# Noise Power Ratio measurement with PSA and Signal Studio NPR

Question asked by nickmmw on Feb 5, 2008
Latest reply on Jul 19, 2010 by tabbott
Posted: Sat Feb 02, 2008 10:07 pm    Post subject: Noise Power Ratio measurement

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Hello,

I have used the Agilent Signal Studio software to create an NPR test stimulus with the following parameters:

- number of tones = 1001
- noise pedestal width = 80 MHz
- notch width = 800 KHz (10 tones in the notch)
- tone spacing = 80 KHz
- Notch depth = 50 dB
- Fcenter = 20 GHz
- using Agilent E8267D VSG and E4448 PSA
- PSA att = 22 dB
- external att = 30 dB
- Pmax of DUT ~ 40 dBm
- Gain of DUT ~ 25 dB

My questions are in regards to the actual NPR measurement on the PSA:
Note that I am writing software with Agilent VEE pro to measure a DUT's NPR, after the creation of an NPR stimulus with the signal-studio-software.

Note that I'm using the 'band-interval-power' marker function on the PSA

- is 'notch depth' and system NPR the same thing?

- the signal studio software reports a notch depth of 50 dB after correction,
how does signal studio compute this notch depth? When we actually measure the DUT, is it accurate to use the same method to calcuate the DUT's NPR as signal studio did? If so, how does signal studio exactly calculate notch depth?

- How does the width of the band-interval-power affect the NPR measurement?

- I am seeing differences in the calculation of NPR with different sizes of band interval - using the 'band-intvl-pwr' function. Why would we see differences? NPR = (pedestal pwr dBm/ Hz divided by notch pwr dBm/ Hz)

- I am seeing large differences in the calculation of NPR with different res-BW setting on the PSA. Any advice on how to select optimum RSB for measuring synthesized noise - in the notch and in the pedestal?

- I would like to detect as deep into the notch as possible - however, I'm concerned with the fact that the tones are 80KHz apart. What res-BW is reccomended ? What's the best way to determine the optimum res-BW and 'band-interval-power width' for this measurment?

- If we were using a 'true' AWGN generator, I guess that the res-BW and size of the 'band-interval-power' would not matter. However, since the noise pedestal is synthesized, any insight on how to perform NPR measurements with the PSA (with highest possible dynamic range) would be very helpful.

thank you,

Nick