Abstract
This FM receiver mainly by FM/AM radio chip CAX1191M, PLL frequency synthesizer BU2614 and monolithic integrated circuit AT89C51 composition. In many monolithic integrated circuits application system, uses the electrical signal and the non-electric signal frequently, transmits the control signal and the data message, by realizes the remote control or the telemetering function, for example light signal, ultrasonic wave signal,electricity pulse signal and so on. But this FM wired/In the wireless remote control broadcast system, uses the double audio frequency electrical signal transmission receive, realizes wired to FM/Radiobroadcasting long-distance control management. This kind of double audio frequency correspondence has the control simply,implementation convenient, the transmission is reliable, moreover construction cost inexpensive characteristic, also is one more commonly used mailing address. The realization monolithic integrated circuit system double audio frequency, this radio has used double audio frequency decoding chip MT8870, demodulates the tonic train signalling from the frequency-modulated signal, and separates the double tonic train signalling from the tonic train signalling to enter the double audio frequency decoding electric circuit implementation letter command to decode, thus carries on the low gear rate using the frequency modulation channel the control command transmission. Mainly take monolithic integrated circuit chip AT89C51 as the control core,the realization assigns thefrequency range the search and the double audio frequency instruction terminal demonstration.
Key words : Receiver；Phase-lock； Double audio frequency；Decoding
