phase-sensitive detector

phase-sensitive detector

An electronic device capable of measuring the difference in phase between a periodic signal and a reference signal in the presence of noise. The signal plus noise is multiplied by a reference waveform whose shape and frequency are similar to those of the signal. Components near zero frequency are produced. When the output is smoothed by a low-pass filter a steady signal results, whose amplitude is related to the amplitude of the required signal and to the phase difference between the required signal and the reference waveform. The device is used, for example, in a phase-switching interferometer to detect the component at the switching frequency in the output of the first detector.

phase-sensitive detector

[′fāz ‚sen·səd·iv di‚tek·tər] (electronics) An electronic circuit that consists essentially of a multiplier and a low-pass circuit and that produces a direct-current output signal that is proportional to the product of the amplitudes of two alternating-current input signals of the same frequency and to the cosine of the phase between them.