SARK110-UserManual v1.3

or can operate in automatic tracking mode. The Multiband mode is a unique feature of the SARK-110, whereby it is able to display simultaneously the pl...

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SARKSARK-110 Vector Impedance Antenna Analyzer User’s Manual Revision 1.3.1 Updated to Firmware Version 0.10.x

This document is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. © Melchor Varela – EA4FRB 2011-2017

SARKSARK-110

User’s Manual

Contents 1

2

3

INTRODUCTION.......................................................................................................................4 1.1

OVERVIEW ...........................................................................................................................4

1.2

MAIN FEATURES...................................................................................................................5

1.3

OVERVIEW OF FUNCTIONS ....................................................................................................6

1.4

PRECAUTIONS ......................................................................................................................7

1.5

REGULATORY COMPLIANCE ..................................................................................................7

OPERATING THE SARK-110 ..................................................................................................8 2.1

SCREEN LAYOUT ..................................................................................................................8

2.2

STATUS SYMBOLS MEANING .................................................................................................9

2.3

MEANS OF INPUT ................................................................................................................10

2.4

MAIN MENU .......................................................................................................................11

2.5

CHANGING THE FREQUENCY ...............................................................................................12

2.6

CHANGING THE SPAN .........................................................................................................13

2.7

CHANGING THE START AND STOP FREQUENCIES .................................................................14

2.8

FREQUENCY PRESETS........................................................................................................15

2.9

USING MARKERS ................................................................................................................16

2.10

CHANGING THE VERTICAL AXIS PARAMETER ....................................................................19

2.11

SAVING AND RECALLING MEASUREMENTS .......................................................................19

2.12

TAKING SCREENSHOTS ...................................................................................................25

2.13

CHANGING THE OPERATING MODE ..................................................................................26

2.14

CHANGING THE SETTINGS ...............................................................................................26

OPERATING MODES.............................................................................................................40 3.1

SCALAR CHART MODE ........................................................................................................40

3.2

SMITH CHART MODE ..........................................................................................................42

3.3

SINGLE FREQUENCY MODE ................................................................................................45

3.4

CABLE TEST MODE (TDR) .................................................................................................49

3.5

FIELD MODE ......................................................................................................................52

3.6

MULTI-BAND MODE ............................................................................................................54

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User’s Manual

3.7

SIGNAL GENERATOR MODE ................................................................................................57

3.8

COMPUTER CONTROL MODE ..............................................................................................61

3.9

BAND SCAN MODE .............................................................................................................63

SPECIAL FUNCTIONS...........................................................................................................65 4.1

TRANSMISSION LINE ADD/SUBTRACT ..................................................................................65

4.2

CIRCUIT MODELS ...............................................................................................................68

4.2.1

Loop Antenna/Coil ................................................................................................68

4.2.2

Capacitor ..............................................................................................................71

4.2.3

Quartz Crystal.......................................................................................................72

4.2.4

Transmission Line ................................................................................................74

4.3

TUNING STUBS...................................................................................................................77

APPENDIX A:

THEORY OF OPERATION..............................................................................79

APPENDIX B:

FUNDAMENTAL PARAMETERS....................................................................81

APPENDIX C:

UPGRADING THE FIRMWARE ......................................................................83

APPENDIX D:

OSL CALIBRATION ........................................................................................84

APPENDIX E:

FREQUENCY CALIBRATION.........................................................................89

APPENDIX F:

DETECTOR CALIBRATION............................................................................90

APPENDIX G:

FREQUENCY PRESETS FILE ........................................................................94

APPENDIX H:

SCALE PRESETS ...........................................................................................95

APPENDIX I:

CUSTOM CABLE SETTINGS .............................................................................97

APPENDIX J:

SPECIFICATIONS ...........................................................................................98

APPENDIX K:

ACKNOWLEDGMENTS ................................................................................101

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1 Introduction 1.1

Overview

The SARK-110 Antenna Analyzer is a pocket size instrument providing fast and accurate measurement of vector impedance, VSWR, vector reflection coefficient, return loss and R-L-C (as series or parallel equivalent circuits). Additionally, the analyzer features a TDR (Time Domain Reflectometer) mode which is intended for fault location and length determination in coaxial cables as well as a programmable RF signal generator. The SARK-110 is intended for standalone operation but also operates when connected to a personal computer in combination with SARK Plots client software for Windows, further enhancing the device’s capabilities. Typical applications include checking and tuning antennas, impedance matching, component testing, cable fault location, measuring coaxial cable losses and cutting coaxial cables to precise electrical lengths. As a signal generator it is ideal for receiver calibration, sensitivity tests and signal tracing. The SARK-110 features a Direct Digital Synthesis (DDS) generator with a range of 0.1 to 230 MHz and a frequency resolution of 1 Hz. The instrument has full vector measurement capability and accurately resolves the resistive, capacitive and inductive components of a load. The measurement reference plane is automatically adjusted via the Open/Short/Load calibration procedure for higher measurement accuracy. Also, the analyzer implements a transmission line addition or subtraction feature in order to make antenna measurements while discounting the effect of the feed line. The user interface, based on a color display, has been designed to be intuitive and easy to use. The graphical impedance displays provide a quick view of the antenna impedance characteristics on a user-selected sweep range. This includes the graphical plot of two userselectable parameters in a scalar chart or a complex reflection coefficient in Smith chart form. To help speed up measurements, two markers are available, both of which are user positionable or can operate in automatic tracking mode. The Multiband mode is a unique feature of the SARK-110, whereby it is able to display simultaneously the plot of an impedance parameter in four scalar charts. This feature is ideal for tuning multiband antennas. Also included is a single frequency measurement mode that presents a complete impedance parameter analysis at a user selectable frequency and displays diagrams of equivalent circuits. The analyzer uses an internal 2MB flash disk for the storage and recall of measured parameters, screenshots, analyzer configuration and firmware updates. This disk is accessible via USB so the measured parameters can be downloaded to a PC for analysis using the ZPLOTS spreadsheet program or the SARK Plots client software for Windows.

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Please let us have your suggestions through the website http://www.sark110.com as we are highly motivated to extend this device’s functionality, based on community requests.

1.2

Main Features •

Pocket size and lightweight



Solid aluminum case



Intuitive and easy to use



Operating modes: Scalar Chart, Smith Chart, Single Frequency, Cable Test (TDR), Field Mode, Multi-band, Signal Generator, Computer Control and Band Scan



Good accuracy over a broad range of impedances



Resolves the sign of the impedance



Manual and automatic positioning tracking markers



Internal 2MB USB disk for the storage of measurements, screenshots, configuration and firmware upgrade



Exports data in ZPLOTS-compatible format for further analysis on a PC



SARK Plots client software for Windows



Lifetime free firmware upgrades



Open to community requested features



Open source Software Development Kit (SDK) including a device simulator for development of user applications

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Overview of Functions

The unit has a Test Port located on its left side, to connect to the device under test. This receptacle accepts straight MCX plug connector types. The product pack includes an MCX to SMA female connector adapter and a 20-cm SMA plug to SMA female cable adapter. The USB port located on the right side facilitates connection to a personal computer for communication and internal battery charging using a compatible mini-USB cable (not included). The unit charges the internal battery when connected to USB. The internal battery charger automatically manages the charge cycle and stops the process when the battery is fully charged. The complete charge cycle takes around 3.5 hours. Slide the Power Switch button located on the right side to the ON position to turn the unit on. An automatic power-off feature can be set for power-saving after a user-specified period of inactivity. Operation is controlled by four buttons and two navigation keys located on the top side of the unit. A 3” TFT color LCD is used to display diagrams.

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Precautions 1. Never connect the unit to an antenna during a lightning storm and windy dry days. Lightning strikes and static discharges can damage the unit and may kill the operator. 2. Static build-up on an antenna may cause damage to the unit when connected. As a precaution, before pluging the coax cable into the analyzer always discharge the antenna by momentarily shorting the center and outer conductors of the connecting coax cable together and then touching the coax connector shell to the analyzer to equalize the charge. After operation, always disconnect the antenna. 3. Maximum safe RF input is 2V peak (+16 dBm). Exceeding this RF level may damage the unit. Note that powerful active transmitters nearby may induce a high RF voltage on the antenna. 4. Test port is DC coupled. Use an external series capacitor for measurement scenarios whereby a DC voltage is present. 5. This product emits a low power RF signal during its active measurement mode. When connected to an antenna system, this radiation may cause interference to nearby communication systems. Connect only for as long is necessary. 6. On first time use, it is recommended saving the factory files in a safe place. Please connect the device to a PC via an USB cable and copy the files in the internal disk to a location in your PC.

1.5

Regulatory Compliance

SARK-110 is certified for CE compliance under regulations EN61000-4-2 and EN55022.

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2 Operating the SARK-110 This chapter provides information about the SARK-110’s basic functionality and user interface.

2.1

Screen Layout

The following figure shows the screen layout in Scalar Chart mode. It shows diagram areas that are the same for all operating modes of the SARK-110. Screen layouts that show specifics for each operating mode are provided in corresponding sections of this manual.

1

Diagram

10

Transmission Line length setting

2

Traces

11

Reference impedance setting

3

Markers

12

Calibration profile

4

Vertical axis labeling

13

Filter setting

5

Horizontal axis labeling

14

Sampling setting

6

Active main menu option

15

Calibration status

7

Submenu

16

Run/Hold status

8

Selected submenu option

17

USB/Battery status

9

Markers information window

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Status Symbols Meaning Calibrated

Calibration status

Not calibrated

Measurements in progress Run/Hold status Measurements on hold

Device operating from USB USB/Battery status

Battery charge status when operating from battery

Disk

Disk write operation in progress

Zoom

Zoom:E

Zoom Extends

(Smith Chart)

Zoom:1o

Zoom 1 Octave

Zoom:1s

Zoom 1 Sixteenth

Zoom:nq

Zoom 1 to 4 (n) Quarter

Sampling

Filter

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st

st

st

th

d/s

Double sampling

r/2

Normal sampling – resolution ½

r/4

Normal sampling – resolution ¼

r/8

Normal sampling – resolution 1/8

ave

Average

smo

Smoothing

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Means of Input

There are four buttons and two navigation keys on the SARK-110.

Navigator A Navigator A is used to navigate within the main menu.

Navigator B Navigator B is used for changing the value of the active option in the main menu (for Freq, Span, Marker1, Marker2, LeftY and RightY) and to navigate within the popup submenus.

Run/Hold [►||] The Run/Hold button is used to control the operating state of the SARK-110: Working or Paused. In the paused state the signal generator and measurement circuits are inactive. Note: when loading a stored data file the analyzer is automatically placed in a paused state.

Select [■] The button is used to activate the popup submenu associated with the highlighted option and for selecting the desired option within the popup submenu. Note: Pressing any other button will cancel a selection.

Save Screen [●] The Save Screen button is used to take a screenshot of the current screen. The screenshot is stored on the internal flash disk.

Save Conf. [▲] The Save Conf. button is used to store the complete analyzer state and settings. The stored state is restored automatically after the device is powered on.

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Main Menu

The main menu is the primary navigation tool. Navigator A is used to change the active menu option. If the Main Menu setup option is enabled, a popup menu is shown automatically when the Navigator A right or left buttons are pressed; see the screenshot below. The active menu option is shown on the top left side of the screen

Figures below illustrate the main menu options available for each mode.

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2.5

Changing the Frequency

There are two methods of editing the frequency (center frequency for sweep modes): (i) Use Navigator A to select «FREQ» in the main menu. Press the Select [■] button to display the popup dialog associated with «FREQ». Then use Navigator B to change the frequency. The frequency will change according to the current frequency multiplier that is highlighted in reverse video. Use Navigator A to change the frequency multiplier position if needed. Press the Select [■] button to validate the frequency selection. Press any other button to cancel the operation. The screenshot below is of the frequency edit dialog, showing the highlighted frequency multiplier positioned over digit 5 (frequency increments of 10 KHz).

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(ii) Use Navigator A to select «FREQ» in the main menu. Then use Navigator B to change the frequency. The frequency will change according to the current frequency multiplier. The frequency multiplier can be changed from the popup dialog, see (i) above. Note: the span range will be adjusted automatically if the resultant upper or lower frequency entry causes it to fall outside operational limits.

2.6

Changing the Span

There are two methods of editing the Span: (i) Use Navigator A to select «SPAN» in the main menu. Press the Select [■] button to display the popup dialog associated with «SPAN». Then use Navigator B to change the span. The span will change according to the current span frequency multiplier that is highlighted in reverse video. Use Navigator A to change the span frequency multiplier position if needed. Press the Select [■] button to validate the span selection. Press any other button to cancel the operation. The screenshot below is of the span edit dialog, showing the span frequency multiplier positioned over digit 7 (frequency increments of 1 MHz).

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(ii) Use Navigator A to select «SPAN» in the main menu. Then use Navigator B to change the span. The span will change according to the current span frequency multiplier. The span frequency multiplier can be changed from the popup dialog, see (i) above.

2.7

Changing the Start and Stop Frequencies

For sweep modes it is also possible specifying the Start and Stop frequencies. Use Navigator A to select «FREQ» or «SPAN» in the main menu and then press Navigator A to change the entry mode. These main menu options will change to display «START» and «STOP». Pressing the Navigator A again will revert to the «FREQ» and «SPAN» entry mode. The screenshot below shows the main menu changed to allow the entry of «START» and «STOP» frequencies.

Operation is similar to the «FREQ» or «SPAN» entry: (i) Use Navigator A to select «START» or «STOP» in the main menu. Press the Select [■] button to display the popup dialog. Then use Navigator B to change the frequency. The frequency will change according to the current frequency multiplier that is highlighted in reverse video. Use Navigator A to change the frequency multiplier position if needed. Press the Select [■] button to validate the frequency selection. Press any other button to cancel the operation. (ii) Use Navigator A to select «START» or «STOP» in the main menu. Then use Navigator B to change the frequency. The frequency will change according to the current frequency multiplier. The frequency multiplier can be changed from the popup dialog, see (i) above.

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2.8

User’s Manual

Frequency Presets

The analyzer provides predetermined frequency and span settings including the amateur radio bands and other suitable settings. Use Navigator A to select «PRESET» in the main menu. Press the Select [■] button to activate the Preset popup submenu. Use Navigator B to highlight the desired preset. Press the Select [■] button to validate the preset selection. Press any other button to cancel the operation. See in the screenshot below the available presets:

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2.9

Using Markers

The SARK-110 has two markers that can either be manually positioned by the user or set to operate in automatic tracking mode. The markers indicate the horizontal and vertical position of the point on which they are positioned. The horizontal position of a marker is shown by a dotted vertical line which extends from the top to the bottom of the measurement diagram. The markers information window, in blue background, shows the frequency (or distance in cable test mode) and the two values that correspond to the plotted values at each of the markers. Use Navigator A to select either «MARK 1» or «MARK 2» in the main menu. Press the Select [■] button to activate the Marker popup submenu. Available options are: «Enable» for activating or deactivating the marker, «Tracking» for selecting the tracking mode, «Info» to display detailed information and «Center» to set the center frequency at the marker position; see screenshot below:

The automatic tracking feature makes positioning of the markers easier, thus helping the user to speed up measurements. The following tracking modes are available:

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SARKSARK-110 •

Peak Min (p)



Peak Max (P)



Absolute Min (m)



Absolute Max (M)



Value Cross Any (X)



Value Cross Up (^)



Value Cross Down (v)

The automatic positioning of markers is activated in the «Tracking» sub-option. Select the tracking mode from any of the modes above and then the applicable parameter to track. In addition, a detection value must be specified for the Cross detection modes. For example, you could set Marker 1 to automatically track the minimum VSWR values in the trace: «MARK 1» «Tracking» «Peak Min» «VSWR»; and Marker 2 to track the crossovers on the 50-ohm impedance value: «MARK 2» «Tracking» «Cross Any» «Z» «50.0». You could also program the unit to detect the bandwidth by setting «MARK 1» «Tracking» «Cross Down» «VSWR» «2.0»; and «MARK 2» «Tracking» «Cross Up» «VSWR» «2.0». Navigator B will be used to move to the different detection points, except for the Max and Min tracking modes where logically there is only a single detection point. The tracking mode for each marker is shown in the markers information window. This information is displayed in red if either the data is not available or if the tracking condition cannot be resolved; otherwise it is displayed in green. The screenshot below shows Marker 1 tracking the minimum value of VSWR and Marker 2, tracking all |Z| crossing at 50-ohms:

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The «Info» option displays detailed information of the readings at the marker position, including the difference in frequency between both markers. One possible use of this feature is determining the VSWR bandwidth of an antenna. Besides, the display includes the calculation of electrical length of a line that will be useful for applications such as tuning stubs; see section 4.3. The «Info» option can be also selected by pressing Navigator A when either «MARK 1» or «MARK 2» are highlighted.

The «Center» menu option can be used to set the center frequency at the marker’s frequency value.

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2.10 Changing the Vertical Axis Parameter In Scalar Chart mode, the SARK-110 can display two traces from any of the available parameters for the vertical axis. Use Navigator A to select either «LEFT Y» or «RIGHT Y» in the main menu. There are two methods of changing the selected vertical axis parameter: (i) Press the Select [■] button to activate the LeftY or RightY popup submenu. Use Navigator B to highlight the desired submenu parameter option. Press the Select [■] button to validate the selection. Press any other button to cancel the operation. The screenshot below shows the available parameters for the vertical axis:

(ii) Use Navigator B when either the «LEFT Y» or «RIGHT Y» option is highlighted. Options are selected sequentially.

2.11 Saving and Recalling Measurements The SARK-110 has the capability to store measurements to the internal disk and recall them either to review the data later in the analyzer screen or to download the data from the USB disk

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to a PC for further analysis using SARK Plots or the ZPLOTS Excel application, available from http://www.ac6la.com/zplots.html. Use Navigator A to select «FILE» in the main menu for data file operations. Press the Select [■] button to activate the File popup submenu. Use Navigator B to highlight the desired submenu File option. «Save Data File» The Save Data File option enables the current measured data to be saved for further review:

After selecting the «Save Data File» submenu option, enter the file name. By default, the file name has the format “sark__xx.csv” (or “sark__xx.tdr” for Cable Test mode), where xx is an automatically assigned number. To change the file name, use Navigator B to change the character value and Navigator A to change the character position highlighted in inverse video. Press the Select [■] button to validate the selection. Press any other button to cancel the operation.

The «Save Data File» option can be also selected by pressing Navigator A when «FILE» is highlighted.

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If the file base name (the name without the xx numbers) is changed, it will be recalled in subsequent save data operations. In the example below, if the file base name is changed to EA4FRB in the first save data operation, then the same file base name will be applied to all subsequent saves of that file.

«Load Data File» To retrieve the stored data, select the «Load Data File» submenu option. A second popup submenu is displayed with a list of available files. Use Navigator B to highlight the desired file. Press the Select [■] button to validate the selection. Press any other button to cancel the operation. Once the file is selected, the data is loaded and plotted.

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«Load Bitmap File» Use the «Load Bitmap File» option to display a captured screenshot. Press the Select [■] button to finalize the operation.

«Browse Bitmaps» Select the option «Browse Bitmaps» from the «FILE» menu to review the captured screenshots. Use Navigator B to select the different bitmaps. Press the Select [■] button to finalize the operation. «Delete File» Use the «Delete file» option to delete a single file on the device disk. When selecting the «Delete File» option a popup submenu will be displayed with the list of available files. Use Navigator B to highlight the desired file. Press the Select [■] button to validate the selection. Press any other button to cancel the operation.

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«Delete All» Use the «Delete All» option to delete all user files. When selecting the «Delete All» option, a confirmation dialog box is activated to prevent an accidental deletion.

«Deep Sweep Save» The deep sweep save function provides the capability of saving measurements with higher accuracy and resolution. It permits a higher number of frequency points to increase the frequency resolution to be specified and uses the higher accuracy settings during the sweep scan; this means a double sampling rate and an average of four measurements per single frequency point. In addition, this function enables a user programmable timeout for the automatic start of measurements to be specified. This function is similar to the self-timer function on cameras. In order to use this function, first set the frequency and span range in any of the sweep modes such as Scalar Chart and then select «FILE» «Deep Sweep Save».

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The procedure is as follows: Enter the file name.

Enter the number of frequency points. Minimum value is 258 and maximum value is 10000.

Specify

an

optional

delay

for

the

automatic start of the measurements (self-timer function).

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SARKSARK-110 When a Delay is specified, a countdown will commence. Otherwise, press the appropriate button to continue.

After completing the sweep scan, the analyzer will save the results of the sweep scan to the file. Notice that the scan time is much longer than usual due to the higher accuracy setting and the additional number of points.

Press the appropriate button to continue.

2.12 Taking Screenshots Press the Save Screen [●] button to capture the current screen. Then enter the file name. By default the file name has the format “sark__xx.bmp”, where xx is an automatically assigned number. To change the file name, use Navigator B to change the character value and Navigator A to change the character position highlighted in inverse video. Press the Select [■] button to validate the selection. Press any other button to cancel the operation.

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Select the option «Load Bitmap File» or «Browse Bitmaps» from the «FILE» menu to review the captured screenshots. Also, they can be reviewed on a PC because they are in Windows bitmap compatible format. Note: the bitmap files use a significant amount of disk (48 or 94kB per screenshot)

2.13 Changing the Operating Mode Use Navigator A to select «MODE» in the main menu. Press the Select [■] button to activate the Mode popup submenu; see the screenshot below:

Use Navigator B to highlight the desired submenu mode option. Press the Select [■] button to validate the selection. Press any other button to cancel the operation.

2.14 Changing the Settings Use Navigator A to select «SETUP» in the main menu. Press the Select [■] button to activate the Setup popup submenu; see the screenshot below:

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Use Navigator B to highlight the desired submenu setup option. Press the Select [■] button to validate the selection. Press any other button to cancel the operation.

Setup – Rotate Screen The Rotate Screen setup menu option can be used to flip the screen so that the device can be used upside down. Use Navigator B to highlight the Rotate Screen submenu setup option. Press the Select [■] button to flip the screen. Repeat the process to flip the screen back.

Setup –Calibration The calibration features are accessible through the Calibration submenu:

Setup – Calibration - OSL See Appendix D:

Setup – Calibration - Frequency See Appendix E:

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SARKSARK-110 Setup – Detector See Appendix F:

Setup – Calibration - OSL Profile See Appendix D:

Setup – Run Mode The Run Mode setup menu option allows setting «Continuous» or «Single Shot» sweep modes.

In continuous mode the analyzer is constantly sweeping provided that it is not in paused state. In single-shot mode the sweep automatically stops on completion. Press the Run/Hold [►||] button to start a new sweep. Notice that in the stop condition the power consumption is reduced, so using single-shot mode helps to increase the battery autonomy.

Setup - Scale The SARK-110 provides three pre-defined scale values: Normal, High and Low as well as automatic scaling. This setting defines the maximum and minimum values for each parameter on the Y axis, see Appendix H:. This setup is valid for the Scalar Chart, Field, Cable Test (Normal and Auto only) and Multi-band modes.

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Setup - Z0 This setup permits the reference characteristic impedance to be changed. The value can be selected from a set of predetermined values or it can be user-specified selecting the Custom option.

Setup - Automatic Power Off This setup permits the automatic power off delay to be selected from a set of predefined times.

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After power-off, press the Select [■] button to resume operation. Alternatively, power off and power on the device using the Power Switch.

Setup - Cable Type The length measurements in the cable test mode and transmission line operations require the proper setting of the cable type. This setup permits the selection of cable parameters from a set of predetermined values for the most popular coaxial cables. Additionally, the user can specify three custom cable settings; see Appendix I:

Setup – Smith Chart Circles This setup enables the display of the constant VSWR circle or constant-Q lines.

The screenshots below show how to configure a VSWR circle set at a value of 5.0.

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The screenshots below show how to configure constant Q-lines set at a value of Q of 1.

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Circles can be disabled by selecting «None».

Setup – Color Theme This setup permits a choice of two color themes: «Black» or «White».

The screenshots below shows graphs with color themes set to «White» and «Black»:

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Setup – Plot Thickness This setup allows a choice of thickness of the diagram’s traces from two options: «Thick» and «Thin». This option is unavailable in the Field Mode graph, where traces are always set to thick.

The screenshots below show graphs with plot thicknesses set to «Thick» and «Thin»:

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Setup – Filter This setup offers the choice of one of two noise reduction filters or none for the Scalar Chart, Smith Chart, Field and Multi-band modes.

The «Average» filter minimizes the noise but at the expense of reducing the measurement speed. Four samples are taken for each measurement frequency and an average from these samples is calculated.

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The «Smoothing» filter is a moving average calculation for each measurement point of the unweighted mean of the previous measurement points. The measurement speed is not affected but there could be a loss of accuracy. The magnitude of the peak or valley of a rapidly changing parameter may be affected. Check the results with and without the filter if there is any doubt.

Setup – Sampling This setup permits a choice of sampling modes: «Normal», «Double», «Normal / Res. 1/2», «Normal / Res. 1/4» and «Normal / Res. 1/8». The «Normal» option is the default setting and provides a good balance between accuracy and measurement speed. The «Double » option is intended for enhanced accuracy measurements, because it reduces measurement ripple by doubling the number of samples taken, but at the expense of a slower sweep speed. This enhancement of the measurements is more noticeable when using automatic scales for measurement over a small range of values. The rest of options are equivalent to «Normal» option, but the sweep speed is faster because the number of frequency measurement points is reduced by half, quarter or octave.

Setup – Buzzer This setup enables control of the analyzer’s sounds. Select «Enabled» to enable all the sounds. Select «Disable Key Click» to deactivate the feedback click sound when pressing the buttons or the navigation keys. Alert and error sounds will continue to be enabled. Select «Disable All» for an all-silent operation.

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Setup – Backlight This setup allows adjustment of the display’s backlight intensity. The range is from 1 to 10, where the higher value corresponds to the higher brightness.

Setup – Units This setup allows configuration of distance units either in meters or feet.

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Setup – Stubs This setup allows configuration of the fraction of wavelength and velocity factor for the tuning stubs feature; see section 4.3.

Setup – Main Menu This setup permits enabling or disabling the main menu.

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SARKSARK-110 Setup – Reset to Factory Defaults This setup permits resetting the analyzer to its default settings.

The internal disk drive can be optionally formatted. Press the Select [■] button to format the disk or any other button if only a reset to factory defaults is required. It is recommended that the disk contents are backed up to a PC as most of the files will be lost during the format. Only the Detector Calibration file (detcalib.dat) and the file associated with the selected OSL Calibration profile are preserved.

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Setup – About The About screen displays copyright information, firmware release number, disk size and free space.

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3 Operating Modes 3.1

Scalar Chart Mode

1

Diagram

9

Reference impedance setting

2

Traces

10

Calibration profile

3

Markers

11

Filter setting

4

Vertical axis labeling

12

Sampling setting

5

Frequency axis labeling

13

Calibration status

6

Active main menu option

14

Run/Hold status

7

Markers information window

15

USB/Battery status

8

Transmission Line length setting

The Scalar Chart mode provides functionality for impedance measurements of antennas, transmission lines and RF circuits. The analyzer performs reflection measurements within a user-specified frequency range, defined by the frequency and the span. The two user-selectable fundamental parameters are displayed as a Cartesian diagram. Up to two markers can be selected to provide precise information in the plotted areas. Their positions can either be userselected or automatically tracked. They are also useful for indicating characteristic points in the plot. Rev 1.3.1 May 22nd, 2017

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Use Navigator A to select «MODE» in the main menu. Press the Select [■] button to activate the Mode popup submenu and use Navigator B to highlight «Scalar Chart» submenu mode option. Finally press the Select [■] button to enter Scalar Chart mode. The analyzer performs measurements and updates the plot continuously if the Run Mode in the «SETUP» menu is set to Continuous. The sweep can be stopped at any time by pressing the Run/Hold [►||] button. If the Run Mode in the «SETUP» menu is set to Single Shot, the sweep automatically stops on completion of a single pass. Press the Run/Hold [►||] button to start a new sweep. The results of the measurements are kept in internal memory and plotted on the display to permit user analysis. The measurements can be resumed at any time by pressing the Run/Hold [►||] button again. Measurement data can be stored at any time on the internal disk by pressing the Save Screen [●] button and restored later for review through different options in the «FILE» menu.

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SARKSARK-110 3.2

Smith Chart Mode

1

Diagram

9

Reference impedance setting

2

Trace

10

Calibration profile

3

Markers

11

Filter setting

4

Constant VSWR circle

12

Sampling setting

5

Frequency start and end

13

Calibration status

6

Active menu option

14

Run/Hold status

7

Markers information

15

USB/Battery status

8

Transmission Line length setting

The Smith Chart mode is equivalent to the Scalar Chart mode but in this case the complex reflection measurements for the user-specified frequency range are displayed in a Smith Chart diagram. Use Navigator A to select «MODE» in the main menu. Press the Select [■] button to activate the Mode popup submenu and use Navigator B to highlight «Smith Chart» submenu mode option. Finally press the Select [■] button to enter into Smith Chart mode. The analyzer performs measurements and updates the plot continuously if the Run Mode in the «SETUP» menu is set to Continuous. The sweep can be stopped at any time by pressing the

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Run/Hold [►||] button. If the Run Mode in the «SETUP» menu is set to Single Shot, the sweep automatically stops on completion. Press the Run/Hold [►||] button to start a new sweep. The trace is painted in two colors: green trace shows the reflection coefficient for the frequencies below the center frequency and red trace for the frequencies above the center frequency. This allows easily identifying the position of the center frequency. The impedance measurement data and marker positions are preserved when changing to the Scalar Chart mode and vice versa. For example, markers can be set at the zero reactance points of the plot (where the plot crosses the X axis) in the Smith Chart mode and see them in Cartesian format in the Scalar Chart mode. There are two zoom choices available. For both options the center is unchanged and the outer circle of the chart can be specified at a VSWR of 5.0 or 2.0.

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SARKSARK-110 3.3

Single Frequency Mode

1

VSWR bar

9

Frequency setting

2

Series impedance complex form

10

Transmission Line length setting

3

Circuit equivalent series

11

Reference impedance setting

4

Series resistance and equivalent

12

Calibration profile

inductance (or capacitance) values 5

Parallel impedance complex form

13

Sampling option

6

Parallel circuit equivalent

14

Calibration status

7

Parallel resistance and equivalent

15

Run/Hold status

16

USB/Battery status

inductance (or capacitance) values 8

Active menu option

The Single Frequency mode provides impedance measurements at a single frequency. All the measured fundamental parameters at the selected frequency are shown in the display. In addition, a VSWR graph is available for a quick visualization of this parameter. As well as the two element equivalent circuit models, both series and parallel circuits are displayed as schematics.

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Use Navigator A to select «MODE» in the main menu. Press the Select [■] button to activate the Mode popup submenu and use Navigator B to highlight «Single Frequency» submenu mode option. Finally press the Select [■] button to enter into Single Frequency mode. The analyzer performs the measurements continuously, unless it is paused by pressing the Run/Hold [►||] button. The measurements can be resumed at any time by pressing the same button again. This mode offers optional VSWR audio feedback. When activated by the menu option «AUDIO», the analyzer produces beeps of different duration as an indication of VSWR. The audio is produced only for VSWR values between 1.0 and 10.0 and the beep duration is shorter for lower values.

There are four presentation modes in single frequency mode.

Select «DISP» «Data» for a tabulated presentation of the readings.

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Select «DISP» «Graphic» for the graphic presentation.

Select «DISP» «Big VSWR» for a presentation mode where the VSWR readings are displayed with a big font for easy viewing.

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Matching Networks is another supported presentation mode. In this mode the analyzer automatically calculates the L/C values in four matching networks. Select «DISP» «Matching Networks» for this presentation mode.

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SARKSARK-110 3.4

Cable Test Mode (TDR)

1

Diagram

8

Zoom mode

2

Traces

9

Cable Velocity Factor Setting

3

Markers

10

Calibration profile

4

Vertical axis labeling

11

Sampling option

5

Distance axis labeling

12

Calibration status

6

Active menu option

13

Run/Hold status

7

Markers information

14

USB/Battery status

Cable Test or Time Domain Reflectometer (TDR) mode is intended to identify potential coaxial cable faults that could disrupt signal transmission. Unlike native TDR test equipment, the method of measurement in the SARK-110 is based on the theory of Frequency Domain Reflectometry (FDR). The analyzer makes swept reflection measurements over the entire frequency range and mathematically transforms the gathered data to Time Domain using an inverse Fourier transform. As a result, the step and impulse responses are plotted on the display, providing information about the location and the nature of any fault. The impulse response trace (green trace) gives an indication of the fault location. The step response trace (red trace) provides an indication of the nature of the fault.

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The vertical axis of the graph displays the reflection coefficient: Rho = -1 for short load, 0 for matched impedance load (ZLoad = Z0), or Rho = +1 for open load. The horizontal axis displays the distance in meters. Use Navigator A to select «MODE» in the main menu. Press the Select [■] button to activate the Mode popup submenu and use Navigator B to highlight the «Cable Test» submenu mode option. Finally press the Select [■] button to enter into Cable Test mode. This measurement requires the user to select the cable’s characteristic impedance and velocity factor. These settings are obtained from the selected cable in the «SETUP»«Cable Type» menu option. As in the other modes, the measurements can be performed continuously or in single shot mode and controlled by the Run/Hold [►||] button, but in this case it takes some seconds for the results to show on the display due to the time it takes to make a full frequency sweep. The distance from the start of the cable to any discontinuity may be found by moving one of the markers over the discontinuity of interest. The distance of the fault from the start of the cable is then shown in that marker’s distance figure. There is a basic zoom feature controllable from the «ZOOM» menu option. This allows zooming into one of the four quarters of the graph or the complete span via the option «Extends». Also available is a zoom option to extend the first octave and the first sixteenth of the graph for short cable lengths. See in the screenshots below the operation of the zoom function in which the measurement of a coaxial cable line of 27.5 meters and Velocity Factor of 0.66 in open condition (unterminated at the other end) is shown below:

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Figures below illustrate the responses of known discontinuities:

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SARKSARK-110 3.5

Field Mode

1

Diagram

9

Reference impedance setting

2

Trace

10

Calibration profile

3

Vertical axis labeling

11

Filter setting

4

Frequency axis labeling

12

Sampling setting

5

Reading (value and Z) at the center

13

Calibration status

frequency 6

Maximum and minimum values

14

Run/Hold status

7

Active menu option

15

USB/Battery status

8

Transmission Line length setting

Field Mode is equivalent to the Scalar Chart mode but simpler to use and with a more legible presentation aimed at operation in the field. The reading at the center frequency is shown using a bigger font. Frequency and magnitude of maximum and minimum points in the trace are shown at the top of the graph. This will be helpful, for instance, in the identification of the frequency and magnitude of the minimum VSWR point.

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Use Navigator A to select «MODE» in the main menu. Press the Select [■] button to activate the Mode popup submenu and use Navigator B to highlight «Field» submenu mode option. Finally press the Select [■] button to enter into Field mode. Operation is similar to the scalar chart mode with some limitations such as only one trace is plotted and the markers feature is not available.

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SARKSARK-110 3.6

Multi-band Mode

1

Diagrams

8

Calibration profile

2

Trace

9

Filter setting

3

Selected band

10

Sampling setting

4

Active menu option

11

Calibration status

5

Frequency and magnitude value for

12

Run/Hold status

13

USB/Battery status

each band 6

Transmission Line length setting

7

Reference impedance setting

The Multiband mode is a unique feature of the SARK-110 to display the plot of an impedance parameter in four scalar charts simultaneously. This feature is ideal for tuning multiband antennas. Additionally, it can be used to display different views of the same band, as a kind of zoom feature. Use Navigator A to select «MODE» in the main menu. Press the Select [■] button to activate the Mode popup submenu and use Navigator B to highlight «Multi-band» submenu mode option. Finally press the Select [■] button to enter into Multi-band mode. Operation is similar to the scalar chart mode but with some limitations such as unavailability of markers and a single trace only. Rev 1.3.1 May 22nd, 2017

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The main menu «BAND» option permits selecting the active band. The selected band is highlighted in the frequency axis of the band graph. Frequency and span settings are applied to the selected band. The detailed measurements at the top of the screen correspond to the selected band as well.

The «CHART» menu option allows enabling or disabling specific charts. The screenshots below show the Band 4 disabled.

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The «Save Data File» function operates in the same way as in other modes. The data for each band of the enabled charts is stored sequentially in individual files. The «Load Data File» loads the data from a file to the selected band only.

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SARKSARK-110 3.7

Signal Generator Mode

The SARK-110 can be used as a programmable RF signal source in Signal Generator Mode. It outputs a sinusoidal RF signal at a frequency programmable from 1 kHz to 230 MHz with eight user selectable amplitude levels ranging from -73 dBm to -10 dBm. In addition, frequency sweeps can be programmed with linear, bi-linear, logarithmic, or bi-logarithmic functions. Additionally, the signal may be modulated in FM and AM modes. This signal generator mode is ideal for receiver testing and alignment, sensitivity tests, RF signal tracing and troubleshooting. Use Navigator A to select «MODE» in the main menu. Press the Select [■] button to activate the Mode popup submenu and use Navigator B to highlight «Signal Generator» submenu mode option. Finally press the Select [■] button to enter into Signal Generator mode. The screenshot below shows the signal generator screen in continuous frequency operation mode. The screen includes the programmed frequency in Hertz and the output power level expressed both in dBm and volts.

Frequency can be changed as usual; see chapter 2.5. For changing the output level, Use Navigator A to select «LEVEL» in the main menu. Use Navigator B to select the desired level or press the Select [■] button to activate the level selection pop up dialog. There are eight selectable output levels ranging from -73 dBm to -10 dBm. The «Maximum» output level setting produces the device’s maximum output signal level that the hardware can support at the assigned frequency. Note that when using this setting there is both a more noticeable amplitude roll off with frequency as well as higher distortion of the output signal.

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The signal generator outputs continuously unless it is paused by pressing the Run/Hold [►||] button. In the Hold state the level graph and power level indicators change to red. Signal generation can be resumed at any time by pressing the Run/Hold [►||] button again.

In frequency sweep mode the signal frequency will sweep between two user-defined frequencies. To change the sweep parameters, Use Navigator A to select «SWEEP» in the main menu and press the Select [■] button to validate the different sweep parameters.

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SARKSARK-110 The following parameters should be supplied: •



Sweep: o

None

Continuous frequency mode

o

Frequency

Sweep frequency mode

o

Continuous

Continuous signal generation

o

Single

Signal generator stops after a single sweep

o

Count:

Signal generator stops when number of sweeps reach count

Repeat:





Function: o

Linear

Linear frequency increase or decrease

o

Log

Logarithmic frequency increase or decrease

o

Bi-Linear

Start-Stop-Stop-Start sweep (Linear)

o

Bi-Log

Start-Stop-Stop-Start sweep (Log)

Start Frequency: o





Number of points: o



Hertz

Stop Frequency: o





Number of steps between start and stop frequency



Delay uS: o

Hertz



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Step time Micro-seconds

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All the sweep parameters are shown on the screen as seen in the screenshot below:

In Amplitude Modulation mode the signal is 50% modulated with a 1 kHz tone. In Frequency Modulation mode the tone frequency is 1 kHz and the frequency deviation is 2.5 kHz.

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SARKSARK-110 3.8

Computer Control Mode

The SARK-110 can be operated from a personal computer using SARK Plots client software for Windows, further enhancing the capabilities of the instrument. There is no need to install a dedicated driver since communication is implemented using the standard USB HID interface. Use Navigator A to select «MODE» in the main menu. Press the Select [■] button to activate the Mode popup submenu and use Navigator B to highlight «Computer Control» submenu mode option. Finally press the Select [■] button to enter into Computer Control mode. The analyzer establishes the USB link when it is connected to a personal computer but only accepts commands from the client in Computer Control mode.

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The command interface specification is open for anyone wishing to develop client software. Source code examples of the communication interface are available for different operating systems. This information is available at the following link: http://www.sark110.com/commands-interface

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SARKSARK-110 3.9

Band Scan Mode 8

6

9

10

7

4

4

3

3

2

1

5

1

Diagram

6

Active menu option

2

Traces

7

Markers information

3

Markers

8

Calibration status

4

Vertical axis labeling

9

Run/Hold status

5

Frequency axis labeling

10

USB/Battery status

The SARK-110 can be used as a rudimentary Spectrum Analyzer in Band Scan Mode. It can be used to scan for nearby signals that may interfere with the measurements or to measure the power of the spectrum of signals in a lab environment. Operation is similar to the Scalar Mode. There are two traces: left axis shows the signal power level (Pwr) and right axis shows the peak hold (Peak). Press the Run/Hold [►||] button twice to reset the Peak trace at any time. The sweep speed is slower than in other modes and is largely proportional to the width of the Span setting. Narrower spans yield faster sweeps. Save Data and Load Data file operations are not available in this mode, but it is possible to capture screenshots as in the other modes. The SARK-110 was not designed as a Spectrum Analyzer so there are a number of limitations when used for this function, such as:

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The power level is not calibrated so the measured power levels are not necessarily accurate.



The input mixer has no image suppression, so on narrow spans, the image will appear at an equal amplitude, see the next screenshot

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4 Special Functions 4.1

Transmission Line Add/Subtract

The SARK-110 provides the capability of subtracting a length of transmission line (transpose to load) or adding a length of transmission line (transpose to input). Use the subtraction feature to discount the effect of the feed line so the measurements will be as if the analyzer were connected at the antenna feed point. Use the addition feature for simulating the effect of a feed line. The transmission line type has to be known in advance. The SARK-110 provides a comprehensive list of cable types and in addition the user can specify up to three custom cable types. The selection of the cable is available in the menu «SETUP» «Cable Type», see the screenshot below:

The transmission line length has to be entered into the «TL LEN» menu option within the Main menu. Use negative quantities for Subtract operations (transpose to load) and positive quantities for Add operations (transpose to input). The pop-up edit dialog is activated by pressing the Select [■] button when the «TL LEN» option is active; see the screenshot below. The value is set by using Navigator B to adjust the digit at each of the current length multiplier positions, shown in reverse video. The length multiplier position can be changed using Navigator A. The length is validated by pressing the Select [■] button. The setting is cancelled by pressing any other button. Note that the length value can be set to zero by pressing the Save Screen [●] button

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The second method for changing the transmission length is simply by using Navigator B when the «TL LEN» menu option is active. The length value will change according the current length multiplier. The length multiplier can be changed from the pop-up transmission line length edit dialog. Since the precise cable length is not normally known in advance, there is a procedure to get the cable length as follows. As a precondition the cable must be unterminated at the far end. Set the SARK-110 to Smith Chart mode and select «PRESET» «Full HF». The Smith Chart will show a spiral from infinite impedance and going towards the center. When setting negative length values, this spiral will be progressively unrolled and transposed to the infinite impedance point when the exact length will be set. Then, if a load is connected at the cable far end, the presence of the transmission line will be discounted. The screenshots below show an example of this in operation. A line of 28.2m of RG-58C/U coax cable is unterminated at the far end. The first screenshot shows the measurement without applying the TL compensation and the last screenshot shows the measurement once the subtract feature has been applied.

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SARKSARK-110 4.2

Circuit Models

The SARK-110 provides advanced analysis features, including the automatic determination of the circuit models of small loop antennas or coils, capacitors and quartz crystals. It is also capable of automatically determining different parameters having to do with transmission lines. It is essential that the analyzer is calibrated before each measurement for accurate results when using these functions. The open, short and load calibration loads have to be connected to the end of the test port extension cable being employed. Please refer to Appendix D on how to carry out the steps for OSL calibration. The measurement results can be saved in a file in tabular format or as a screenshot. The Circuit Models function is only available in the Single Frequency Mode. Select «MODE» «Single Frequency» to change to the Single Frequency mode. Then select «CMODEL» in the main menu and the desired function in the pop-up submenu.

4.2.1

Loop Antenna/Coil

This function determines the equivalent circuit model of small loop antennas or coils. This function is specially tailored for the measurement of antennas for HF RFID applications. Detailed usage

of

this

function

is

described

in

the

Application

Note

available

at:

http://www.sark110.com/application-notes/rfid-appnote The measurement procedure is as follows:

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Select the file name and press [●] or select [▲] when the results are not to be saved in a file

Enter the desired operating frequency

Enter the desired scan limit

After some seconds the results are shown on the screen. A

screenshot

can

be

captured

by

selecting [●]

The figure below describes the measured parameters:

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The internal procedure performed by the analyzer is as follows: the analyzer measures the impedance at 1 MHz and at the desired operating frequency (e.g. 13.56 MHz). Then it searches for the antenna’s self-resonant frequency and measures the impedance at that point. The following parameters are extracted from these measurements: Fra

Self-resonant frequency of the antenna

Z(Fop)

Z at operating frequency

Z(Fra)

Z at resonant frequency

Rs

Equivalent resistance at F = 1 MHz

La

Equivalent inductance at F = 1 MHz

Rp

Equivalent resistance at the self-resonant frequency

The antenna capacitance is calculated with the following equation:

Ca =

1 La × (2 × π × Fra ) 2

The series equivalent resistance of the antenna at the operating frequency Fop = 13.56 MHz is calculated with the following equation:

(2 × π × Fop × La ) 2 Ra = Rs + Rp

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The quality factor is calculated using the following equation:

Qa =

4.2.2

2 × π × Fop × La Ra

Capacitor

This function determines the equivalent circuit model of capacitors. The measurement procedure is as follows: Select the file name and press [●] or select [▲] when the results are not to be saved in a file

Enter the operating frequency

After some seconds the results are shown on the screen. A

screenshot

can

be

captured

by

selecting [●]

The figure below describes the measured parameters:

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The internal procedure performed by the analyzer is as follows: the analyzer measures the impedance at 1 MHz and at the desired operating frequency. Then it searches for the selfresonant frequency and measures the impedance at this point. The following parameters are extracted from these measurements: Fra

Self-resonant frequency of the capacitor

Z(Fop)

Z at operating frequency

Z(Fra)

Z at resonance frequency

Ca

Equivalent capacitance at F = 1 MHz

Ra

Equivalent resistance at the self-resonant frequency

The capacitor’s parasitic inductance is calculated with the following equation:

La =

1 Ca × (2 × π × Fra ) 2

The quality factor is calculated using the following equation:

Qa =

4.2.3

1 (2 × π × Fop × Ca × Ra ) Quartz Crystal

This function determines the equivalent circuit model of quartz crystals. Detailed usage of this function is described in the Application Note available at: http://www.sark110.com/applicationnotes/equivalent-circuit-determination-of-quartz-crystals The measurement procedure is as follows:

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Select the file name and press [●] or select [▲] when the results are not to be saved in a file

Enter the frequency value, which should be close to the expected resonant frequency of the crystal

Enter the estimated crystal bandwidth value

After some seconds the results are shown on the screen. A

screenshot

can

be

captured

by

selecting [●]

The figure below describes the measured parameters:

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The process starts by searching for the series and parallel resonant frequencies. The start scan frequency is taken from the specified frequency value. The resonant frequencies are identified in the singularities where the impedance changes from pure capacitive (phase value close to -90º) to pure inductive (phase value close to +90º). The resonant frequencies are then obtained from the frequency points where the measured phase value is close to zero. After determining the series and parallel resonant frequencies, the series resistance (Rs) at the series resonant frequency is measured. Then the parallel capacitance (Co) is measured. This value is measured from a frequency that is 2.5 MHz below Fs and 2.5 MHz above Fp. From these measurements, the rest of the parameters are derived: The value of series capacitance (Cs) is given by:

 Fp  Cs = 2 × Co ×  − 1  Fs  The value of the series inductance (Ls) is given by:

1 4 × π × Fs 2 × Cs

Ls =

(

2

)

Finally, the quality factor of the crystal (Q) is calculated by:

Q=

1 Ls × Rs Cs

4.2.4

Transmission Line

This feature allows you to automatically measure different parameters having to do with transmission lines, namely: •

The line's characteristic impedance (Z0)



The true velocity factor



The matched line loss in terms of dB over the total line length and in dB/100m

The measurement procedure is as follows:

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Select the file name and press [●] or select [▲] when the results are not to be saved in a file

Enter the start frequency

Enter the stop frequency

Enter the transmission line length

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Connect the transmission line terminated with an open circuit. Press the appropriate button to continue, or to exit.

Connect the transmission line terminated with a short circuit. Press the appropriate button to continue, or to exit.

After some seconds the results are shown on the screen. A

screenshot

can

be

captured

by

selecting [●]

Note: Try to keep the electrical length of the line exactly the same between the open and short termination conditions. Ideally you would terminate the line with the same standard loads that were used to do the Open Short Load (OSL) calibration. Z0 is obtained by calculating the arithmetic mean of the real part of the following equation for all the frequency points:

Z 0 = Zoc × Zsc The calculation of the Velocity Factor (VF) and matched loss is more convoluted and will not be explained here. The relevant information is that the VF is provided at the upper frequency and the matched loss is provided at the maximum frequency and the arithmetic mean for all frequency points.

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Tuning Stubs

The SARK-110 facilitates making ¼-λ, ½ -λ and other coaxial stubs with the help of Markers Info feature. Markers Info dialog box provides information about the electrical length of the line. Let’s illustrate the tuning procedure with an example. In this case we are going to make a ¼-λ stub with a RG-58 cable for a frequency of 20 MHz. Select «SETUP» «Stubs» and specify the fraction of wavelengths (wavelength=0.25) and the cable velocity factor (VF=0.66).

From the Scalar Chart mode, select start frequency of 1 MHz and stop frequency above the desired frequency –in this case it is set to 30 MHz. Move Marker 2 to the frequency closed to the desired frequency (20 MHz) and select «MARK 2» «Info». At the bottom of the dialog box, “Len” indicates the calculated electrical length of the coax cable.

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Cut a piece slightly longer than this value and connect to the analyzer. Move the Marker 1 to the point where
Select «MARK 1» «Info». The readings show a length of 3.037m and a length difference (M1M2) of 0.563m, which is the excess length of the piece of coax cable. Cut a piece slightly shorter than this value and repeat the process until getting to the expected value.

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Appendix A:

Theory of Operation

The block diagram below illustrates the main functional blocks of the SARK-110 Antenna Analyzer:

The SARK-110 comprises four main sections: a signal generator used as an active source, a bridge to provide signal separation, two tuned receivers that downconvert and detect the signals and a microcontroller and display for calculating and reviewing the results. The signal generator is provided by a single chip dual direct digital synthesizer (DDS) AD9958 from Analog Devices, which generates a sinusoidal signal for impedance measurement and a local oscillator signal for the tuned receivers (mixers). One of the DDS channels operates at the specified test frequency and the other is programmed to operate just 1 kHz above it, which is the value of the intermediate frequency. The DDS has an internal oscillator driven by an external 24 MHz crystal and is able to multiply this clock internally by a user configurable factor of 4 to 20, so the maximum internal clock frequency is 480 MHz. In general the DDS can be configured to generate a frequency of up to one third of the clock frequency but in this design, due to the external reconstruction filter, it is possible to achieve an output frequency of up to 230 MHz. The amplitude level of the DDS channel’s output is frequency dependent and it is reduced with increasing frequency following a SIN(X)/X function. The SARK-110 software compensates for this amplitude rolloff effect by using the capability of the DDS to adjust the amplitude level of the output signal, so the analyzer maintains a flat output amplitude. The output of each of the DDS channels is differential and is amplified by a dual high speed current feedback amplifier working in differential input mode and with output in single ended Rev 1.3.1 May 22nd, 2017

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mode. Most DDS designs use a broadband balun transformer to convert to single end mode but because of the restricted height available in the SARK110 enclosure a silicon-based solution was chosen. The output of each amplifier is followed by elliptic low pass filters with a cut-off frequency of 230 MHz. These filters reduce the level of spurious high frequency components that appear in the output of the DDS. These high frequency components consist of aliases at multiples of the internal clock frequency as well as other spurs. For impedance measurement a resistive bridge is used because of its simplicity and good frequency response, working down to DC. In the bridge the voltage across one resistor is proportional to the voltage being applied to the circuit under test and the voltage across another resistor is proportional to the current flowing into the circuit connected to the analyzer’s test port. Both the magnitude and phase are measured. The ratio of the two corresponds to the impedance we want to measure. One of the mixers is used for the voltage measurement and the other for the current measurement. The output of the mixers is the 1 kHz I.F. signal which is then amplified and filtered with a bandpass filter before digitizing. Identical mixer and amplifier circuits are used for both the voltage and current sensing paths. Any small differences in the gain and phase shift of these two signal paths are taken care of by the calibration process. The core of the analyzer is an STM32F103 microcontroller from STMicroelectronics. This microcontroller incorporates the high-performance ARM Cortex M3 32 bit core operating at 72 MHz, a Flash memory of 256 kB, SRAM of 48 kB and an extensive range of I/O and peripherals including a USB device controller and three 12-bit ADC converters. The digitizing of the 1 kHz I.F. signal is done by two independent 12-bit ADC converters contained in the STM32 MCU. These two converters operate simultaneously and are synchronized, so providing good accuracy for the phase measurement. The two sets of digital data from the voltage and current sensors are analyzed using an optimized implementation of the discrete Fourier transform that works with a single bin. This produces the amplitude and phase of the 1 kHz fundamental signal and cancels out any DC component due to offsets in the operational amplifiers. The load impedance magnitude is the voltage amplitude divided by the current amplitude. The phase angle of the impedance is the difference in the phase angles of the voltage and current. Knowing these two parameters, we can calculate the equivalent resistance and reactance of the load impedance. The rest of the parameters such as VSWR, reflection coefficient, etc. are derived from the measured impedance value.

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Appendix B: Abbreviation

Fundamental Parameters Parameter

Description

Rs

Series resistance

Resistive value of a series impedance

Xs

Series reactance

Reactance value of a series impedance

Rp

Parallel resistance

Resistive value of a parallel impedance

Xp

Parallel reactance

Reactance value of a parallel impedance

|Zs|

Magnitude of a

Represents the absolute magnitude of the ratio of the

series Impedance

voltage difference amplitude to the current amplitude.

| Z |=
Impedance Angle

(R

2

+X2

)

It is a measure of the phase angle of the ratio of the amplitude of the voltage to the amplitude of the current, expressed in degrees.

VSWR

Voltage Standing

It is a measure of how efficiently radio-frequency power is

Wave Ratio

transmitted from a power source, through a transmission line and into a load (for example, from a power amplifier through a transmission line and into an antenna).

RL

Return Losses

Return loss is the negative of the magnitude of the

(S11 dB)

reflection coefficient in dB.

RL = 20 × log 10( Rho) CL

Cable Losses

Measurement of insertion loss of a cable in dB. The measurement should be performed by applying a short circuit at the cable end.

CL = ABS ( |Rho|

RL ) 2

Magnitude of a

It is a measure of the absolute magnitude of the ratio of

Reflection

the amplitude of the reflected wave to the amplitude of the

Coefficient (Rho or

incident wave.

S11)

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Abbreviation
Parameter

Description

Reflection

It is a measure of the phase angle of the ratio of the

Coefficient Angle

amplitude of the reflected wave to the amplitude of the

(S11 Angle)

incident wave.

 RhoI  Ph = a tan    RhoR  %Ref Pwr

Percentage of

% RPwr = Rho 2 × 100

Reflected Power

Q

Quality Factor

It is defined as the ratio of the energy stored in a component to the energy dissipated by the component.

Q= Cs

Ls

X R

Series

Equivalent series capacitance at the measurement

Capacitance

frequency

Series Inductance

Equivalent series inductance at the measurement frequency

Cp

Lp

Parallel

Equivalent parallel capacitance at the measurement

Capacitance

frequency

Parallel Inductance

Equivalent parallel inductance at the measurement frequency

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Appendix C:

Upgrading the firmware

The SARK-110’s firmware may be upgraded via USB as described in the following steps. This procedure

assumes

you

have

downloaded

the

appropriate

update

file

from:

http://www.sark110.com/files/firmware The downloaded file has the following format: SARK110-APP-x.y.z.dfu.zip

Where x.y.z is the incremental version number.

The downloaded file has to be unzipped to produce an update file in the format: SARK110-APP-x.y.z.dfu Procedure: 1. Connect the SARK-110 to the PC with a USB cable 2. Locate the SARK’s USB flash drive unit using the File Explorer of your PC 3. Copy the firmware file, e.g. SARK110-APP.x.y.z.dfu to the SARK’s USB flash drive unit 4. Do a safe eject of the SARK’s USB flash drive unit from your computer 5. Power off the SARK-110 and power it on again while simultaneously holding down the Run/Hold [►||] button 6. The Device Firmware Upgrade screen prompts you to install the firmware file 7. If several firmware files are on the SARK’s USB flash drive unit, use Navigator B to select the file to load 8. The firmware upgrade will commence after pressing the Select [■] button 9. Once complete, press the “Save Conf” [▲] button, which will reset the analyzer and run the upgraded firmware 10. Select «SETUP»«About» and check if the firmware version shown on the screen agrees with the installed one

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Appendix D:

OSL Calibration

The SARK-110 provides a calibration procedure to compensate for the stray capacitance and impedance of the external test fixture, e.g. the extension cable. This should be performed every time the external test fixture is changed as well as periodically. Calibration is performed by using a set of calibration plugs consisting of: an Open circuit, a Short circuit and a calibrated Load having the same value as the reference impedance. These loads are connected sequentially to the end of the test lead as instructed on the screen as described below. To set the reference impedance, please refer to Setup - Z0 in the chapter 2.14. The place where these loads are connected during the calibration is called the Reference Plane.

The analyzer performs a series of measurements with these loads, calculating error coefficients that are stored in a file that is automatically loaded each time the analyzer is run. These error coefficients are used to correct the measured values. The number of calibration points is fixed to 400. The frequency range for the calibration can be programmed by the user, allowing setting a narrower frequency span for higher resolution measurements. The device supports the storage of up to eight calibration profiles. These profiles can be associated to different test port adapters or different frequency ranges. Select «SETUP» «Calibration» «OSL Profile» to set the active calibration profile. The active profile is shown in the status line; e.g. “P0” for profile 0.

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After selecting the calibration profile, the profile characteristics are shown in a popup dialog.

Once the calibration profile has been selected, choose «SETUP» «Calibration» «OSL» to start the OSL calibration procedure.

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The calibration procedure is as follows: Enter the start frequency (default is the lower frequency limit)

Enter the stop frequency (default is the upper frequency limit)

Enter an optional name for the profile

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Connect the open load. Load status is indicated by the color of the |Rh| indicator. Green denotes load good status. Press the appropriate button to continue, or to exit.

The calibration progress will be shown in the display bar.

Connect the short-circuit load. Load status is indicated by the color of the |Rh| indicator. Green denotes load good status. Press the appropriate button to continue, or to exit.

The calibration progress will be shown in the display bar.

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Connect the reference load. Load status is indicated by the color of the |Rh| indicator. Green denotes load good status. Press the appropriate button to continue, or to exit.

The calibration progress will be shown in the display bar.

Press the appropriate button to apply the new calibration settings, or to cancel them.

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Appendix E:

Frequency Calibration

This setup permits the frequency synthesizer to be calibrated to 1 Hz. The calibration operation is available at «SETUP» «Calibration» «Frequency».

To calibrate the synthesizer, select «Frequency» from the «Calibration» submenu and adjust the frequency while measuring it with an accurate frequency counter or, alternatively, zero-beat it against WWV. Use Navigator B to change the frequency. The frequency will change according to the current frequency multiplier that is highlighted in reverse video. Use Navigator A to change the frequency multiplier position if needed. When an exact 10 MHz output is obtained, press the Select [■] button to permanently store the setting. For best accuracy, turn on the unit for at least 10 or 15 minutes before calibrating. Press the Save Screen [●] button if the default setting needs to be restored.

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Appendix F:

Detector Calibration

This procedure performs alignment of the SARK-110’s internal measurement circuits. This operation is done once at the factory and it is not necessary for the user to repeat it, but the procedure is detailed for completeness. This procedure comprises a calibration phase and an optional detector-test phase to check the detector circuits. For Detector calibration, the Short load is connected directly at the Test port; see the figure below. For the optional detector test phase, the following loads are required: 50, 100 and 200ohm.

Before performing this operation it is strongly recommended that the file containing the factory results, detcalib.dat, is backed up to enable a restore, if needed. Select «SETUP» «Calibration» «Detector» to start the detector calibration procedure.

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The calibration procedure is as follows:

Connect the short load. Load status is indicated by the color of the voltage and current detector indicators. Green denotes a load good status. Press the appropriate button to continue, or to exit. The calibration progress will be shown in the display bar.

The calibration is completed. The calibration coefficients are shown at the bottom of the screen, for information. Press the appropiate button to apply the new calibration settings, or to cancel them.

Press the appropiate button to go to the optional Detector Test, or to exit.

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Connect the 0-ohm load. Load status is indicated by the color of the voltage and current detector indicators. Green denotes a load good status. Press the appropriate button to continue, or to exit.

Connect the 50-ohm load. Load status is indicated by the color of the voltage and current detector indicators. Green denotes a load good status. Press the appropriate button to continue, or to exit.

Connect the 100-ohm load. Load status is indicated by the color of the voltage and current detector indicators. Green denotes a load good status. Press the appropriate button to continue, or to exit.

Connect the 200-ohm load. Load status is indicated by the color of the voltage and current detector indicators. Green denotes a load good status. Press the appropriate button to continue, or to exit.

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Press the appropiate button to repeat the test, or to exit.

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Appendix G:

Frequency Presets File

Default frequency presets can be modified by the user by supplying a special text file stored on the analyzer’s disk. The file name must be “presets.txt” and the format for each band entry in the file is as follows:

legend, start_freq, stop_freq, def_mul_freq, def_mul_span, marker1_freq, marker2_freq Where: o

legend: string to be displayed in the preset menu (max length: 20)

o

start_freq: start frequency, specified in MHz

o

stop_freq: stop frequency, specified in MHz

o

def_mul_freq: default multiplier for setting the frequency

o

def_mul_span: default multiplier for setting the span

o

marker1_freq: default marker 1 frequency, specified in MHz

o

marker2_freq: default marker 2 frequency, specified in MHz

Example: 600M: 500 KHz,

0.1,

0.9,

3, 4, 0.2,

0.5

160M: 1.8 MHz,

1.3,

2.3,

4, 5, 1.8,

2.0

80M: 3.6 MHz,

1.6,

5.6,

5, 6, 3.5,

3.8

60M: 5.3 MHz,

3.3,

7.3,

5, 6, 5.2,

5.5

40M: 7.1 MHz,

5.1,

9.1,

5, 6, 7.0,

7.2

30M: 10.1 MHz,

8.1,

12.1,

5, 6, 10.1,

10.2

HF RFID: 13.5 MHz, 11.5,

15.5,

5, 6, 13.0,

14.0

20M: 14.2 MHz,

12.2,

16.2,

5, 6, 14.0,

14.4

17M: 18.1 MHz,

16.1,

20.1,

5, 6, 18.0,

18.2

15M: 21.2 MHz,

19.2,

23.2,

5, 6, 21.0,

21.5

12M: 24.9 MHz,

22.9,

26.9,

5, 6, 24.8,

25.0

11M: 27.8 MHz,

25.8,

29.8,

5, 6, 27.0,

28.0

10M: 29 MHz,

26.0,

32.0,

6, 7, 28.0,

29.7

6M: 51 MHz,

48.0,

54.0,

6, 7, 50.0,

52.0

4M: 70.1 MHz,

68.1,

72.1,

5, 6, 70.1,

70.2

2M: 145 MHz,

142.0, 148.0, 6, 7, 144.0, 146.0

Full HF,

0.1,

32.0,

Full Span,

0.1,

230.0, 7, 7, 75.0,

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6, 6, 10.0,

20.0 150.0

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Appendix H:

Scale Presets

The following tables show the default scale presets: Normal Rs Xs Rp Xp |Zs|
Min 10 -500 10 -500 10 -100 1.00 -40 0 0 -190 0 0 -10000 -100 -10000 -100

Max 1000 500 1000 500 1000 100 25.00 0 20 1.0 190 100 20 10000 100 10000 100

Scale Log Linear Log Linear Log Linear Log Log Log Linear Linear Linear Linear Linear Linear Linear Linear

Low Rs Xs Rp Xp |Zs|
Min 0 -125 0 -125 0 -100 1.00 -20 0 0 -190 0 0 -1000 -10 -1000

Max 250 125 250 125 250 100 10.00 0 10 1.0 190 100 20 1000 10 1000

Scale Linear Linear Linear Linear Linear Linear Log Log Log Linear Linear Linear Linear Linear Linear Linear

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High Rs Xs Rp Xp |Zs|
Min 10 -2500 10 -2500 10 -100 1.00 -60 0 0 -190 0 0 -100000 -1000 -100000 -1000

Max 5000 2500 5000 2500 5000 100 100.00 0 30 1.0 190 100 50 100000 1000 100000 1000

Scale Log Linear Log Linear Log Linear Log Log Log Linear Linear Linear Linear Linear Linear Linear Linear

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Default scale presets can be modified by the user by supplying special text files stored on the analyzer’s disk. The file names for each of the scales have to be the following: •

«Scale» «Normal»



«Scale» «High»

“scal_hig.txt”



«Scale» «Low»

“scal_low.txt”



«Scale» «Auto»

“scal_aut.txt”

“scal_def.txt”

The files must contain an entry for each parameter with the following syntax: min,max,log {Y,N}

Note that logarithmic scales do not accept negative ranges.

Example (file name “scal_def.txt”): 10,1000,Y

#Rs

-500,500,N

#Xs

10,1000,Y

#Rp

-500,500,N

#Xp

10,1000,Y

#|Zs|

-100,100,N

#
1.00,25.00,Y

#VSWR

-40,0,N

#RL

0,20,N

#CL

0,1.0,N

#|Rho|

-190,190,N

#
0,100,N

#%Rp

0,20,N

#Q

-10000,10000,N

#Cs

-100,100,N

#Ls

-10000,10000,N

#Cp

-100,100,N

#Lp

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Appendix I:

Custom Cable Settings

The SARK-110 allows the user to specify three custom cable settings by supplying a special text file stored on the analyzer’s disk. The file name must be “custcab.txt” and the format for each cable entry in the file is as follows:

legend, Z0, VF, K0, K1, K2

Where: o

legend: string to be display in the preset menu (max length: 20)

o

Z0: characteristic impedance

o

VF: velocity factor

o

K0: DC resistance, dB/100ft

o

K1: coefficient for conductor loss, dB/100ft

o

K2: coefficient for dielectric loss, dB/100ft

Example: Test cable 1,

50,

0.68, 0.063897,

0.192292,

0.000051

Test cable 2,

60,

0.78, 0.073897,

0.193292,

0.000061

Test cable 3,

70,

0.88, 0.083897,

0.194292,

0.000071

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Appendix J: General

Specifications •

Frequency range: 100 kHz to 230 MHz



Frequency resolution: 1 Hz



Frequency stability: ± 30 ppm



Sine wave output



RF Connector: MCX socket



Output power: ≈-10 dBm (0.1mW, 70.7mV rms) into a 50-ohm load



Sweep time (Scalar Chart/Smith Chart/Field Mode): 3 seconds (Sampling: Normal), 5 seconds (Sampling: Double), 1.5 seconds (Sampling: Normal - Res. 1/2), < 1 second (Sampling: Normal – Res. ¼ and 1/8)



Sweep time (FDR): 6 seconds



Frequency Resolution: 258 points per sweep (258 to 10000 in deep sweep mode)



Return loss dynamic range: 0 to -60 dB



VSWR dynamic range: 100:1 maximum



Impedance reading in open circuit: 60000 (@1 MHz)



Measurement limits: |Z| < 100K, |R| < 100K, |X| < 100K, |Rho| < 0.98, C < 100 nF, L < 100 mH, -180 < ϴ < 180

Measured

Complex impedance (series and parallel) and reflection coefficient in

Parameters

rectangular and polar form, VSWR, return loss, reflection power percentage, quality factor, equivalent capacitance, equivalent inductance

Operating Modes

Scalar Chart, Smith Chart, Single Frequency, Cable Test (TDR), Field, Multi-band, Signal Generator, Computer Control and Band Scan

Features Common • Presets for amateur radio bands To Most Modes

• Adjustable reference impedance • Save to disk and recall functions • Three available fixed scale options and automatic scaling • Presets for popular coaxial cables • Add/subtract transmission line • Black or white color schemes

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SARKSARK-110 • Adjustable plot trace widths

Scalar Chart Mode • Graphical plot of two user-selected parameters in a rectangular chart • Two markers with manual or automatic positioning • Display detailed parameters for center frequency or any of the two marker positions Smith Chart Mode

• Plots complex reflection coefficient in Smith Chart form • Two markers with manual or automatic positioning • Display detailed parameters for center frequency or either of the two marker positions

Single Frequency

• Display all parameters for a single frequency

Mode

• Graphical representation of series and parallel impedance equivalent • VSWR Audio feedback • Circuit models and automatic LC matching network calculator

Cable Test Mode

• Range: ≈ from 2 to 250 m • Displays step and impulse responses

Field Mode

• Graphical plot of one user-selected parameter in a scalar chart with enhanced legibility • Display max and min values

Multi-band Mode

Display rectangular charts for four bands simultaneously

Signal Generator

• Frequency range: 1 kHz to 230 MHz

Mode

• Programmable output level from -73 dBm to -10 dBm into a 50-ohm load • Continuous, frequency sweep, AM and FM modulation modes • Linear, logarithmic, bi-linear and bi-logarithmic sweep modes

Markers

Tracking modes: Peak Min, Peak Max, Absolute Min, Absolute Max , Value Cross Any, Value Cross Up, Value Cross Down

Interface

• Full color 3” TFT LCD 400 x 240 pixels • 4 dedicated buttons • 2 navigation keys

PC Interface

• USB Mini-B receptacle • USB 2.0 Full Speed Composite Device:

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Storage

o

Mass Storage Class (internal disk)

o

HID Class (Computer Control mode)

• 2 MB internal disk FAT compatible • USB Mass Storage • Screenshot save and recall feature • Measurement data save and recall feature • Possibility of files with user definable frequency presets, scale settings and three custom cable types • Measurement data files compatible with SARK Plots and ZPLOTS programs

Calibration

• Automated Open/Short/Load calibration with up to eight stored profiles • 400 calibration points • Frequency calibration

Measurement

• Single conversion superheterodyne

Architecture

• Two independent measurement channels for simultaneous voltage and current measurement for precise phase measurement • Two synchronized 12-bit analog to digital converters

Processor

72 MHz STM32 MCU with 256kB Flash and 48kB SRAM

Power

• 3.7V 1000mAh Internal Lithium-Polymer battery • USB for operation and charging • Automatic Power Off functionality (disabled, 5, 10, or 30minutes) • Autonomy ≈ 2.5 hours • Charge time ≈ 3.5 hours

Environment

Operating temperature: 0ºC to 50ºC

Dimensions

98 * 60 * 14.5 (mm)

Weight

120g

Package Content

• SARK-110 x 1 with built-in battery • MCX to SMA female connector adapter x 1 • SMA plug to SMA female 8” (20-cm) cable adapter x 1

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© Melchor Varela – EA4FRB 2011-2017

User’s Manual

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Appendix K:

Acknowledgments

• I would like to offer a special thanks to the Seeed Studio team for making this product a reality. • The analyzer schematics and layout have been developed using the DesignSpark PCB tool. Product information is available at: www.designspark.com/pcb • The analyzer firmware has been developed using the Lite edition of the Atollic TrueSTUDIO

®

for STM32. Product information is available at: www.atollic.com • FAT File System was provided by the ChaN, FatFs module. • The STM32 firmware and USB library are provided by STMicroelectronics. • Many thanks to Dan Maguire, AC6LA, for the great ZPLOTS MSExcel application: http://www.ac6la.com/zplots.html

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© Melchor Varela – EA4FRB 2011-2017