Hi Just as with PM noise, AM noise is a “that depends” sort of thing. The first dependency is on your test gear. If the AM noise was well below the PM noise, would you be able to measure it? Equally, if you are doing something like a diode detector - can it measure AM below XXX dbc? If the detector is only good to -120 dbc/Hz, you aren’t going to “see” -130 ….
Noise on output state supply lines can generate AM. In some cases the stage is a better AM modulator than PM modulator. Limiting (like with a logic gate) is not going to pass AM noise well. That combination can make for some “interesting” noise profiles. One “old time” assumption for wide band noise is that there is no process that will generate AM independent of PM. Thus they will always be in an equal power relationship. The key phrase here is wide band. Think in terms of notching out the carrier and looking at the result on a spectrum analyzer in this case. One of the classic arguments for an AGC or for certain types of limiters in oscillators is AM to PM conversion. The concern here is “close to carrier” rather than far removed. There certainly are examples tossed around where AM noise is significantly higher than PM noise at low offsets. So, no data that I can share. Maybe a few things in there will be of help. Bob > On Jan 2, 2018, at 2:55 PM, Attila Kinali <[email protected]> wrote: > > Hi, > > I am currently looking at noise calculations that deal with AM and PM noise. > To check whether the calculations make sense, I am looking for some numbers > of the white noise floor AM and PM noise levels of signal sources. > Unfortunately, almost everyone only deals with PM noise and hardly > anyone mentiones AM noise levels. The best I could find sofar is [1] > which supports the notion that AM noise is so far below PM noise, that > it is insignificant. Does someone else have more data and would be willing > to share? > > Attila Kinali > > > [1] http://www.wenzel.com/documents/amnoise.htm > > -- > It is upon moral qualities that a society is ultimately founded. All > the prosperity and technological sophistication in the world is of no > use without that foundation. > -- Miss Matheson, The Diamond Age, Neil Stephenson > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
