CIRCUIT FOR DERIVING A QUALITY SIGNAL DEPENDENT ON THE QUALITY OF A RECEIVED MULTIPLEX SIGNAL

摘要

In a circuit for deriving a quality signal dependent on the quality of a received multiplex signal in a stereo radio receiver. The multiplex signal contains a sum signal (L+R) in the base band, an auxiliary carrier modulated with a difference signal (L-R) and a pilot signal at half the frequency of the auxiliary carrier, the multiplex signal in digital form is multiplied by a reference carrier obtained from a scanning pulse generated in the radio receiver in two phase positions mutually offset by 90 DEG . The mixed signals obtained by the multiplication are multiplied by a correction signal to form corrected mixed signals which are added and taken together with the sum signal to a matrix circuit to form stereo audio signals (L, R). The mixed signals are also multiplied by the other correction signal. The products of these multiplications are subtracted from each other and low-pass-filtered.