| 摘要 |
PURPOSE:To realize the reception of the AM stereo broadcast of plural systems through a receiver, by making active a signal processing means suited to the system of the received signal based on a pilot signal. CONSTITUTION:An AM stereo broadcast electric wave, which contains the pilot signals which are different according to the systems and is obtained by giving the modulation of amplitude to an angle modulated wave which is generally expressed by cos[omegact + phi(t)], is received 1. The IF signal is demodulated by an envelope wave detector 3 to be applied to a matrix circuit 5 in the form of a sum signal as well as to a system changeover switch SW7 and a multiplier 8 via a buffer 6. At the same time, the difference signal of the IF signal is demodulated by an FM wave detector 4, and then the IF signals applied to an LPF9 and an equalizing amplifier 10. The output of FM wave detection is applied to the multiplier 8 when a system changeover switch SW11 is on. The pilot signals extracted through the LPF9 are detected by circuits 13, 14 and 16 according to the systems, and the switches SW11, 7 and 12 are driven in accordance with each detection output. As a result, the circuit 5 can reproduce both stereo and monaural signals. |
