Two Instruments, Complex Stimulus-Response Measurement

When you have two instruments, you can perform stimulus-response measurements by measuring the stimulus signal with one instrument, and the response signal with the other instrument. Unlike the other two methods, this method requires that you create two separate VSA measurements.

Observe maximum input power limits. See the technical specifications for your measurement hardware to determine the maximum input limits.

Some Keysight signal generators provide user power limiting (e.g. to set a max input power level to your DUT Device under Test: An acronym used to describe some type of electrical apparatus connected to test instrumentation. The apparatus can range from a single component to a complex subsystem such as a mobile phone, base station or MSC.). This is generally found in the AMPTD menu ("User Power Max" for the N5182A MXG).

When you have two X-Series analyzers of the same model (e.g. two MXA's), it may be possible to combine them into a single Analyzer Configuration and treat them as a single instrument with two channels. In this case, see the Dual X-Series Analyzer Configuration Measurement topic for setting up the Analyzer Configuration, and then use the Multi-channel Instrument stimulus-response measurement procedure instead of this one.

Initial Setup

  1. Connect the measurement instruments to your computer. See the Creating Hardware Configurations topic for more information.

    These instruments will be referred to as Instrument 1 and Instrument 2.

  2. If you are using an Keysight signal generator as the stimulus, connect the 10 MHz Megahertz: A unit of frequency equal to one million hertz or cycles per second. OUT of one of the measurement instruments to the REF IN of the signal generator and REF IN of the other measurement instrument.

  3. Connect the stimulus signal to your DUT and to Channel 1 of Instrument 1 (using a coupler, for example).

  4. Connect the output (response) of the DUT to Channel 1 of Instrument 2.

  5. Configure the VSA

    1. Preset the VSA (File > Preset > Preset Setup). This will reset the VSA back to a basic Vector measurement.

    2. Select the Analyzer Configuration that contains your Instrument 1 (from step 1)

      Click Utilities > Hardware > Analyzer and choose from the list.

    3. Set the center frequency

      Click MeasSetup > Frequency to open the MeasSetup dialog and then set the Center parameter.

    4. Set the Span (also in the MeasSetup dialog)

      Span must be the same for both stimulus and response signals.

    5. Set Main Time Length

      Click the Time tab in the MeasSetup dialog. See Choosing the Time Length for a discussion on choosing an appropriate time length.

      To increase the range of the Main Time Length parameter, select the MeasSetup > ResBW > Frequency Points > Auto check box.

    6. Set the range (Input > Analog > Range) or click the Auto-range button in the toolbar to ensure the best dynamic range for an accurate measurement.

    7. Create a new Vector measurement

      Click MeasSetup > New Measurement > Vector. This should also set the selected measurement shown in the VSA toolbar to the new measurement (Meas02).

    8. Repeat steps b-f for the newly created measurement except select Instrument 2 in step b.

  6. Open the Measurements dialog

    Click MeasSetup > Measurements

  7. Configure triggering

    These steps will configure the VSA to use the Trig Out synchronization feature of the VSA to loosely synchronize the acquisitions of multiple measurements (so that you do not have to provide an external trigger signal to both instruments).

    1. Connect the External Trigger OUT of Instrument 1 to the External Trigger IN of Instrument 2.

    2. Select the Trig Out check box for Meas01.

    3. Set Instrument 2 to External trigger

      Make sure Meas02 is the selected measurement in the VSA toolbar, and then click Input > Trigger and set Style to External.

Measure Stimulus-Response

  1. Run both measurement by clicking the Restart button in the Measurements dialog and verify that your stimulus and response signals appears as expected.

  1. Add Graph traces

    1. Add a new trace to the VSA (Click Trace >  )

    2. Select the type of Graph trace you want (Click Trace > Data > Graph).

      Initially, you might want to view AM Amplitude Modulation - CW modulation using amplitude variation in proportion to the amplitude of the modulating signal. Usually taken as DSB-LC for commercial broadcast transmissions and DSB-SC for multiplexed systems./AM, AM/PM, and Gain Compression. Then, when you are trying to track down the cause of a high-EVM Error vector magnitude (EVM): A quality metric in digital communication systems. See the EVM metric in the Error Summary Table topic in each demodulator for more information on how EVM is calculated for that modulation format. event, you might want to view the Delta EVM Time, Stimulus Time, and Response Time traces.

    3. Configure Graph Settings (click Trace > Graph Settings)

      You can skip steps i-iii. They are shown for your reference (the Auto selection should choose the correct data in this scenario).

      1. Clear the Auto check box

      2. Set Stimulus Data to Meas01 - Ch1 Main Time

      3. Set Response Data to Meas02 - Ch1 Main Time

      4. Customize any of the other settings as desired.

    4. Autoscale the trace

      When you don't see any data, the trace may be outside the limits of the trace grid. Try right-clicking in the center of the trace grid and choosing Auto Scale.

    5. Repeat a-d to add more Graph traces if desired.

      Instead of configuring each Graph trace in step c, you can configure one trace and skip step c for the other Graph traces. Once you are finished adding the Graph traces, select the configured trace and click Copy To > All Traces.

  2. Run the measurement

    Click the Restart button in the toolbar.

See Also

Measurement Overview