The PAR Meter: Characteristics of a New Voiceband Rating System

The peak-to-average ratio (PAR) meter provides a single number measure of the quality of circuits used for transmitting voiceband data signals. A PAR system consists of a generator and a receiver connected to opposite ends of a transmission network to be tested. The generator transmits a precise repetitive pulse through the system, and each pulse is dispersed by the distortions that it encounters. Then, the receiver responds to the pulse envelope peak and to the pulse envelope full-wave average and indicates the ratio on a zero suppressed scale. New equipment to obtain this measure has been designed to avoid ambiguities when used on systems with nonlinear distortion or phase intercept distortion. The PAR concept is reviewed, and the techniques used in this second-generation equipment to overcome these ambiguities and the affects of various distortions on the new meter's response are described. Also, PAR signal spectrum objectives and the measurement sensitivity to circuit parameters are listed.