Keysight N9000A Manual

Also see for EXA X-Series N9010A: Configuration guide Measurement guide Measurement guide Manual Measurement guide

Contents

Keysight N9000A Manual Manual pdf 33 page image

33SCPI Programming FundamentalsTechniques for Improving Measurement PerformanceRFBurst triggering depends on its establishment of a valid triggering reference level, based on previous bursts. If you onlyhave a single burst, the peak detection nature of this triggering function, may result in the trigger being done at thewrong level/point generating incorrect data, or it may not trigger at all.Making a Single Burst MeasurementTo achieve consistent triggering and valid data for this type of measurement application, you must synchronize thetriggering of the DUT with the instrument. You should use the instrument’s internal status system for this.The first step in this process is to initialize the status register mask to look for the “waiting for trigger” condition (bit 5).Use :STATus:OPERation:ENABle 32Then, in the measurement loop:1. Send query :STATus:OPERation:EVENt? to clear the current contents of the Operation Event Register.2. Send query :READ:PVT? to initiate a measurement (in this example, for GSM Power versus Time) using the previoussetup. The measurement then waits for the trigger.Make sure attenuation is set manually. Do not use automatic attenuation, as this requires an additional burst todetermine the proper attenuation level before the measurement can be made.3. Create a small loop that polls the instrument for a status byte value of 128. Then wait 1 msec (or 100 ms if the displayis enabled) before checking again, to minimize bus traffic. Repeat these two commands until the condition is set, toensure that the trigger is armed and ready.4. Trigger the DUT to send the burst.5. Retrieve the measurement data.Optimize GSM Output RF Spectrum Switching Measurement (N9071A MeasurementApplication)For ORFS (switching), setting the break frequency to zero (0) puts the instrument into a measurement setup where it canuse a direct time measurement algorithm, instead of an FFT-based algorithm. The non-FFT approach is faster.However, remember that the break frequency for ORFS (modulation) measurements must be >400 kHz for validmeasurements, so, if you are making both types of measurements, you will need to change the break frequency.To make Power Measurements on Multiple Bursts or Slots useCALCulate:DATA:COMPress?The Calculate/Compress Trace Data Query is the fastest way to measure power data for multiple bursts/slots. (For detailsof the command, see the Programming the Analyzer chapter of any X-Series Help file or Users & Programmers ReferencePDF.) There are two reasons for this:1. It can be used to measure data across multiple, consecutive slots/frames with just one measurement, instead of aseparate measurement on each slot,2. It can pre-process and/or decimate the data so that you only return the information that you need, which minimizesdata transfer to the computer.Example: you want to do a power measurement for a GSM base station where you generate a repeating frame with 8different power levels. Using the Waveform measurement, you can gather all the data with a single CALC:DATA:COMP?acquisition.