Sampling and switching-sampling-type phase-sensitive detectors

摘要

Two circuits which accept two sinusoidal waveforms of same frequency with phase difference 0 and provides two dc output voltages in which one dc output voltage is proportional to the quadrature component sin 0 and the another is proportional to the in-phase component cos 0, by using (1) sampling and (2) switching-sampling techniques, are described in this article. In sampling-type phase-sensitive detector (PSD), a phase-shifted signal V_I of peak value V_s is sampled by a sampling pulse generated during positive zero crossings of the reference signal V_R. Then the sampled output will be V_Q = V_S sin θ, where θ is the phase difference between V_I and V_R. This is illustrated graphically in this article. In the switching-type PSD, the need of a 90° phase shifter is eliminated to obtain quadrature component. Verification of the feasibility of circuit configuration is established by way of test results on a proto type.