Q. What do you mean by FM Stereo?
IT shows the block diagram of an FM stereo transmitter and an FM stereo receiver. The following notation is used:
• fL(t), fR(t): Left and right messages that undergo preemphasis and are then added to yield f 1(t) and differenced to give fd(t).
• f2(t): Given by signal fd(t) when it DSB-modulates (with carrier suppressed) a 38-kHz subcarrier.
• f3(t):Alow-level pilot carrier at 19 kHz that is included to aid in the receiver's demodulation process.
• fs(t): Final compositemessagewhen f1(t), f2(t), f3(t), and SCA(subsidiary communications authorization) are all added up.
• SCA: A narrow-band FM waveform on a 67-kHz subcarrier with a total bandwidth of 16 kHz. It is a special signal available to fee-paying customers who may desire to have background music free of commercials or nonaudio purposes such as paging.
• NBPF: Narrow-band band-pass filter.
• LPF, BPF, and NBPF: Appropriate filters that select the spectrum portions corresponding to f1(t), f2(t), and f3(t), respectively.
The output signal-to-noise power ratio is smaller in FM stereo than in a monaural system with the same transmitted power, messages, and other parameters. With a loss as high as 22 dB, many FM stations can tolerate the loss because of the high power being transmitted.