Analysis of phase noise effect on microwave attenuation precision measurement using a heterodyne receiver

The phase noise effect on microwave attenuation precision measurement using a lock-in amplifier (LIA) is studied. A frequency domain phase noise modeling is used to analyse the phase sensitive detection made by the LIA. The error bound for the magnitude and phase of LIA measurement has been established. The theoretical prediction of the maximum magnitude and phase fluctuation in LIA output agrees with the measured data quite well. This analysis is important for estimating the maximum attenuation measurement error caused by the phase noise of microwave sources and its uncertainty contribution to microwave attenuation measurement.