Today, I tried to measure the NF of RF power amplifer with Aglient Spectrum analyzer and Signal generator. I know there is three ways to measure NF,
1. use NF analyzer (I don't have one)
2. Q-factor (I don't have two noise source)
3. Gain method. NF = Pn(tot)@output+174dbm-Gain
The problem as following,
1. The Pn(tot)@output is ~-70dbm[pwr in 0dBm, Gain(RFPout-RFPin):32dB, PA is working(Vcc(3.5v), Vpc(2.2v, 25%DC)), center frequency 1710MHz]. So base on the result, the NF of PA should be ~68dB:-(. it is impossible.
My question are
1. Did I do something wrong during test NF?
2. Did the formula right for cal NF by Gain method?
3. Do I need to set the fixed RBW for Spectrum Analyzer? Is there any relationship between NF and RBW setting for SpecAnalyzer?
4. Could anyone provide me some other ways to test it with my available equipment? as well as any helpful appnote.