FM receiver comprising a circuit arrangement for determining the field strength of FM transmitters

Claim 1

In an FM receiver, a circuit for determining field strength of at least two FM transmitters operating at different frequencies, said circuit comprising: an FM demodulator which produces at its output an output signal with a characteristic that indicates when the FM receiver is tuned to one or the other of said different frequencies, said output signal then having an amplitude value determined by the field strength of the FM transmitter to which the FM receiver is tuned, a comparator having a first input coupled to the output of the FM demodulator and a second input coupled to a source of reference voltage, said comparator deriving at its output a binary output signal determined by said output signal characteristic, an integrator stage having an input coupled to the output of the comparator and having an output at which is produced an activation signal only in response to said output signal characteristic of the FM demodulator, and means for evaluating signals indicative of FM transmitter field strength and which has first and second inputs coupled to the output of the FM demodulator and to the output of the integrator stage, respectively, such that said first input of the evaluating signal means receives the FM demodulator output signal without a substantial delay.