AM Stereophonic signal receiver with electric field strength detection

摘要

An AM stereophonic receiver in which degradation of the quality of reproduced sound due to a decreased electric field strength is prevented. A main signal detector produces a sum signal representing the sum of first and second channel signals while a sub signal detector produces a difference signal representing the difference therebetween. The sum signal is coupled directly to a matrix circuit while the difference signal is coupled through a variable control type low-pass filter and a monophonic/stereophonic switch to the matrix circuit. The low-pass filter is controlled by a detection signal representative of the electric field strength of the received signal to reduce high frequency components when the electric field strength decreases below a predetermined value. The low-pass filter is bypassed when the electric field strength is sufficiently high.