FM multiplex broadcasting receiver for receiving RDS and DARC signals

DETAILED DESCRIPTION The present invention is conceived to provide a receiver of simple constitution capable of receiving FM multiplex broadcasts in either or both of the RDS or DARC systems.
In order to achieve this object, an FM multiplex broadcasting receiver according to the present invention includes a DARC signal demodulating circuit and an RDS signal demodulating circuit.
The DARC signal demodulating circuit includes a crystal oscillator which generates a reference clock for demodulating DARC signals, while the RDS signal demodulating circuit includes a clock generating circuit for generating a reference clock for demodulating RDS signals from a signal of the crystal oscillator.
According to one aspect, the clock generating circuit is a PLL circuit which comprises a first frequency divider for dividing an output of the crystal oscillator, a phase comparator connected with the first frequency divider, a VCO connected with the phase comparator, and a second frequency divider connected with the VCO for dividing an output of the VCO and then forwarding the output to the phase comparator.
The output of the VCO is used as a reference clock for demodulation of the RDS signal.
According to this aspect, the ratio of the frequency division number of the first frequency divider to the second frequency divider is set equal to the ratio of the frequency of the reference clock for demodulation of the DARC signal to the frequency of the reference clock for demodulation of the RDS signal.
Although in this aspect, the DARC signal demodulating circuit and the RDS signal demodulating circuit are composed of distinct LSIs, these circuits may also be composed of a single LSI.