Compensative phase meter with lock-in detection

A compensative phase meter is described. It consists of two phase detectors, one integrator and one voltage-controlled phase shifter. Its operation is similar to that of a phase locked loop (PLL) except that the voltage-controlled oscillator in the PLL is replaced by a voltage-controlled phase shifter in the phase meter. Unlike other phase meters, no bias of the phase estimate occurs even when the signal is well below the noise level. The performance of the system is examined. The dependence of parameters such as phase jitter and acquisition time on loop and noise parameters is found. The influence of nonlinear characteristics of the phase shifter and the phase detector on the system performance is investigated.