A High-Performance Phase-Sensitive Detector

A phase-sensitive detector is described that enables the retrieval of signals submerged 90 dB (voltage) below the noise level. Operation over four decades of signal amplitude (a fullscale linearity error of 0.01 percent) is possible for a frequency range of 0-150 Hz. Design features are offered allowing an experimenter to construct the device from inexpensive components and be assured a predictable performance.