New Mode of Operation of a Phase Sensitive Detector

The PS detector plays an important role in the instrumentation for spectroscopy and radio astronomy and in atomic frequency standards. Usually the phase sensitive detector is preceded by a narrow-band-pass amplifier centered on the reference frequency or one of its harmonics. Such a procedure discards useful information contained in the other harmonics. It is suggested that the narrow-band amplifier be replaced by a wide-band one and that the reference waveform be shaped to be identical with that of the desired signal. First order calculations show that this method gives slightly better sensitivity than the conventional one. Also, discrimination against coherent signals of other waveforms can be obtained. If a differentiating circuit is inserted into either the input or the reference circuit, the detector output is an odd function of the phase angle. Therefore, this arrangement can be used as a sensor for a servo system used to lock the phase of the reference oscillator to the signal.