AnsweredAssumed Answered

Add extra external amp to measurement system

Question asked by iamstupid on May 12, 2011
Latest reply on Jun 30, 2011 by Dr_joel
Hello Experts in the forum,
This is Sean. Sorry for bother, I am having trouble to measure some pretty low power noise.
I currently have a Spectrum Analyzer with preamp installed, but this only give me about 1dB margin for pass even with the input port of SA terminated. So it is quite easy to see failure when I really do measurements. I am planning to add extra amp to the system.

Let's assume something:

The measurement result with SA input terminated and Preamp on is -161dBm/Hz
The measurement result with UUT connected is -159dBm/Hz. (with Preamp on)
The Criteria (or say, the limit) is -158dBm/Hz.

Can I add another external amplifier before the signal enters into the Spectrum Analyzer so that the result can be lower?

If yes,

1. What is the consideration for the external amplifier? Can I add a 30dB AMP? (It is confirmed there is no other large RF noise except the noise desired to measure)

2. what is the right way to calculate the actual noise level generated by the UUT?

3. With those values, what should be the actual result? And what should be the noise floor of the whole system?

4. Can I shutdown the internal preamp and using the external 30dB AMP and say this is PASS?

Really sorry for bother, but I do need your kindly support for clarify myself.

best regards, Sean