Consumer Electronics

SUM AND DIFFERENCE OF SIGNALS

Although the (L + R) signal is all the listener to a monophonic program needs, the proper reception and reproduction of stereo programs requires the use of an additonal (L–R) signal. This signal is produced at the transmitter by inverting (phase changing by 180 degrees) the R signal (making it negative, or –R) and adding it in its negative form to the L signal. The resulting (L–R) signal, as well as the (L+R) signal, are transmitted on the f.m. broadcast carrier. The two signals are received and separated at the receiver. Then, in the stereo receiver, they are added together to form the L signal alone, and the (L–R) signal is subtracted from the (L+R) signal to form the R signal alone. This is shown mathematically ...