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Problem with PSA E4446A automatic digital averaging restart

Question asked by jjt2119 on Jul 19, 2007
Latest reply on Sep 25, 2007 by peiwen
I am using a E4446A PSA (remotely through GPIB interface) to measure the primary harmonic of on-chip ring oscillators in a CMOS variability study.

However, it seems that there is poor VDD decoupling (on-chip) resulting in considerable phase noise and as such, when measuring the center of the primary mode the lobe moves around considerably (as to be expected).

To compensate for this I would like to digitally average the PSD using logarithmic averaging to get an "average primary mode frequency".  The problem is that, as stated in the user manual (page 80) averaging is restarted when:

"Averaging restarts when any of the following occurs:

- a new average number is entered
- any measurement related parameter (e.g., center frequency) is changed
- Restart is pressed
- Single Sweep is pressed"

Clearly the second point is a problem and as such, the averaging keeps restarting due to the phase noise causing the center frequency to shift about.

Does anyone know of a work around for this problem, or a way to force the averaging to continue without automatically restarting?

Jonathan Tompson