Luis Cupido wrote: > Related to this, I have a question in my mind for sometime. > > How close to a decent phase-noise setup are we if > we down convert and use a low frequency spectrum analyzer ? > (downconverting with the best XTAL LO we can imagine). > > My target is microwaves and millimeter waves so I have to > down convert anyway, Or then I have to live with what my > spectrum analyzer show me (a tek 492, in my case). > > --- > > Rephrasing the question, how much better are the low frequency > spectrum analyzers comparing to the microwave spectrum > analysers (in phase noise I mean)? > > > Any comments ? > > Luis Cupido. > ct1dmk. > > P.S.(I know that I'm limites to 100Hz RBW with my 492... and > I would like also to measure closer than that ) > > Luis
The latest spectrum analyser offerings from Agilent have similar phase noise floors for both the millimeter wave and low frequency spectrum analysers. However the low frequency analysers have a lower "flicker" noise corner. The noise floor of a good double balanced mixer is still 30-40dB lower than that a spectrum analyser. Thus you are stuck with using a low bandwidth phase lock loop to get down to the mixer noise floor. Alternatively a dual (first conversion uses analog mixers, 2nd conversion uses DSP techniques) conversion Costas receiver using 4 mixers and 4 ADCs should go down to -170dBc @ offsets of 100Hz or so when correlation techniques are employed. Its a pity the TSC5120A doesnt allow independent access to all 4 of its ADC inputs so a quad of external mixers can be employed to extend the technique to the millimeter wave region. All you need is 4 high resolution ADCs and an offset generator or 2. A couple of high end sound cards may be suitable at least for testing the concepts. Bruce _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.