Reducing errors, complexity, and measurement time of PM noise measurements

It is shown that a novel measurement technique based on the two-oscillator technique and the addition of a noise source in series with the reference oscillator can significantly reduce calibration time for accurate PM (phase modulation) measurements in oscillators and other components compared to the traditional two-oscillator technique. This technique also significantly reduces the measurement time and improves the accuracy of three-cornered-hat measurements. Measurement complexity is greatly reduced. The noise source is used to generate a known level of PM noise (PMCAL) for calibrating the product of mixer sensitivity and amplifier gain with Fourier frequency. This can be used to correct for PLL (phase-locked loop) effects when PMCAL is larger than the residual phase noise in the oscillator under test. PMCAL is typically constant to ±0.1 dB for Fourier frequencies from 0 to 5% of the carrier (maximum width typically less than 500 MHz). When the PMCAL is off, the noise added to the reference signal is typically less than -150 dBc/Hz at 1 Hz and -190 dBc/Hz at 10 kHz for carrier frequencies of 5 to 100 MHz