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Phase noise measurement / delay line - RF Cafe Forums

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

Joined: Fri Nov 02, 2007 3:45 am
Posts: 10
Location: germany
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



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