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
- can it be right ??
any comments about
the mistake ??
mny thanks
mac
