Phase sensitive detection as a means to recover signals buried in noise

Phase sensitive detection is formalized in order that its operation can be understood and its practical use optimized. The theory explains how narrow bandwidth amplification is achieved in order to reduce the noise content of a measurand and how the process can be considered simply as a multiplier followed by a low-pass filter. The responses to various excitation and measurand forms are derived for signals ranging from the simple sinusoids to the more complicated signals produced when modulating interference fringes and stabilized laser cavities.