One thing you may consider is multiplying your source and reference up to a much higher frequency and then mixing them together, using the mixer as a phase detector, to a low frequency for measurement. Problem being is that the phase noise of most modern oscillators, somewhat removed from the carrier, is way way down and most often below the noise floor of the instrument used to try ad measure it. Of course another question is where does the carrier stop and the noise starts? Naturally it all depends on the intended application. Keep in mind the 20*log(N)factor. So, if you take a 10 MHz oscillator and multiply it to 1 GHz the phase noise will have increased by 40 dB/Hz, a much easier to measure number. Of course you do have to be careful to make sure that the noise contribution of your multipliers is minimal, and, fortunately it usually is. 73 - Mike
Mike B. Feher, N4FS 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of David Kirkby Sent: Sunday, April 24, 2005 9:53 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Phase noise measurements - getting started. How is the best way to make phase noise measurements, starting from limited test kit? Methods I've seen rely on a low noise oscillator - not a lot of use if you don't know the noise performance of any of your oscillators. Another assumes your two oscillators each contribute the same amount of noise, which is probably not true on old oscillators, even if they are the same model. A third seems a bit more promising - the use of 3 oscillators and solving a set of simultaneous equations. I've not looked at the maths of this, but assume that it will not work too well if two oscillators are quite good, and a third bad. I should soon have a 5370B time interval counter with its own oscillator, plus an oscillator I want to test. I also have access to a 8 or so year old spectrum analyser (never recalibrated), scopes, mixers, lock-in amplifiers and general lab kit. My pocket money does not quite stretch to the latest all singing all dancing kit from Agilent. -- Dr. David Kirkby, G8WRB Please check out http://www.g8wrb.org/ of if you live in Essex http://www.southminster-branch-line.org.uk/ _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
