Essential Nonlinearity of Phase-Sensitive Detector Characteristics

The effect of essential nonlinearity of phase-sensitive detector characteristics is studied and determined theoretically in detail, assuming that the input signal is a sine wave in the presence of additive narrow-band Gaussian noise. Minimum, maximum, and limiting values of nonlinearities of detector characteristics as functions of the input signal-to-noise ratio and the phase angle between the input signal and the reference wave are determined by means of computer-aided analysis. A set of curves that can be used to evaluate in detail the essential nonlinearities of detector performance and characteristics over a wide range of operating conditions and significant parameters is presented. Particular emphasis is placed on the determination of optimum detector operating conditions for minimum essential nonlinearities in wide-band Fourier-transform high-resolution nuclear magnetic-resonance and electron-spin-resonance spectrometers.