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E8636B/C: Using ext trigger to speed a measurement sequence

Question asked by dhfx on Mar 9, 2009
Latest reply on Mar 16, 2009 by dhfx
We have a T/R module tester system in the field containing an E8363B PNA, and the application involves taking a repeated series of S-parameter (specifically S21) measurements over 32 DUT attenuator settings followed by 16 DUT phase-shifter settings, all at the same frequency and power level; then repeating at two (or more) other frequencies, for a total of (16 + 32) * 3 = 144 individual S21 gain-and-phase measurements. (The actual measurements are pulsed, with an external modulator on the Source Out from the PNA and the modulator output coupled into R1.)

At present it looks like each of the repeated measurements is commanded separately (from an external host controller), then the value is read and tested, the DUT is advanced to the next step, and the process repeats. What I want to do is speed up the overall testing by reducing the time for the repeated measurements as the DUT is advanced through the attenuation and then the phase steps at each frequency. It looks as if this could be done as a single sweep consisting of three CW subsweeps (one per frequency), triggered externally in point mode in synchrony with the commands to the DUT. The triggers and DUT commands will be generated by an FPGA to eliminate software latency.

What I understand so far is that we can download an app as a user macro to the PNA. When the macro is started it sets up the measurement sweep and enables the ext trigger. On each trigger the PNA does one measurement, stores the value, raises Ready for Trigger and waits for the next trigger. At the end of the sweep, a CHANNEL_SWEEP_COMPLETE event occurs, and an OnEvent handler sets a flag for the macro main, which sees the flag and then formats and writes all the S21 gain & phase values to a .s2p file.

What I am asking is if my understanding so far is correct, or if there is a more appropriate mode of operation that minimizes latency bebtween successive measurements. Any helpful responses will be appreciated.

David Friedman
Sr. Principal Engr.
Symtx, Inc.