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Phase noise measurement / delay line - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


 Post subject: Phase noise measurement / delay line
Posted: Tue Jan 22, 2008 11:16 am 
 
Captain
User avatar

Joined: Fri Nov 02, 2007 3:45 am
Posts: 10
Location: germany
hi,
i am new to phase noise measurements and i
want to measure phase noise of an oscillator
at first i tried direct measuremnt with a fsek spectrum analyzer from r&s but
i quit because my oscillator is quit better than the lo of the spec

so i want to try the delay line or autocorrelation method cause the setup may be much quicker than refernce source method.
to verify my measurement result i want to measure the phase noise of my signal generator ( smt03 r&s)first

setup: signal generator fout=1ghz/ 14dBm feeding a 6dB power splitter.
from power splitter via delay line ( approx 8.5ns) to mixer lo port and the other port of the power splitter via a variable phase shifter to rf port of the mixer.
the if port of the mixer is connected to a 200khz lowpass followed by a 40dB low noise op-amp

if i look at the output of the amplifier with my oscilloscope i can perfectly adjust the phase shifter for zero volts DC -
in an application note ( Phase noise and AM noise measurement in frequency domain from Lance/Wendell D,.. ) i read that after that i have to calibrate this setup -
i frequency modulate the carrier with 15kHz and choose fm-deviation to get first null of the carrier ( checked with spectrum analyzer)

but what do i do next ??
as i understand the application note : i now have to measure the 15khz sideband at the opamp output and calculate the calibration factor -
if i do this with my spectrum analyzer i get approx -50dbm sideband power and calibration factors of 37.89mhz/volt :smt017 - can it be right ??

any comments about the mistake ??

mny thanks

mac

_________________
regards
mac




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