Abstract A signal seeking system for use in an FM stereo multiplex receiver is disclosed wherein the receiver includes tuning, intermediate frequency amplifying and detecting stages. A search mechanism, for example, a search motor, is provided for varying the tuned frequency of the tuning stage. When the 19 KHz. pilot signal from a stereo broadcast is received, a first output signal is provided. Also, when the output of the intermediate frequency amplifying stage is of a sufficient amplitude at the predetermined intermediate frequency of the receiver, a second output signal is provided. The first output, indicative of the reception of a stereo broadcast, and the second output, indicative that the receiver is tuned to the carrier frequency of the stereo station, are applied to a coincidence circuit which supplies an output to the search mechanism which stops the tuning operation at the frequency of the received stereo broadcast. Automatic frequency control is supplied to the tuning stage as the search mechanism is stopped for fine tuning the receiver to the received stereo broadcast.
In a stereo FM receiver including tuning, intermediate frequency amplifying and detecting stages, the combination of: search means for varying the tuned frequency of said tuning stage; stereo sensing means responsive to the detected output of said detecting stage for providing a first signal when a stereo broadcast is being received; IF sensing means responsive to the output of said intermediate amplifying stage for providing a second signal when the output of said intermediate amplifying stage reaches a predetermined amplitude; coincidence means responsive to said first and second signals for providing a third signal; and stop means for stopping said search means from varying the tuned frequency of said tuning stage at substantially the tuned frequency of said stereo broadcast.
Claim 2
Dependent Claim
120 words
In a stereo FM receiver including tuning, intermediate frequency amplifying and detecting stages, the combination of: search means for varying the tuned frequency of said tuning stage; stereo sensing means responsive to the detected output of said detecting stage for providing a first signal when a stereo broadcast is being received; IF sensing means responsive to the output of said intermediate amplifying stage for providing a second signal when the output of said intermediate amplifying stage reaches a predetermined amplitude; coincidence means responsive to said first and second signals for providing a third signal; and stop means for stopping said search means from varying the tuned frequency of said tuning stage at substantially the tuned frequency of said stereo broadcast.
Claim 3
Dependent Claim
46 words
The combination of claim 1 including: AFC means for applying automatic frequency control signals from said detector stage to said tuning stage in response to said third signal, with said tuning stage being fine tuned in response thereto to the tuned frequency of said stereo broadcast.
Claim 4
Dependent Claim
37 words
The combination of claim 2 wherein FM stereo multiplexed signals including a 19 kHz. pilot signal are being transmitted and wherein: said stereo sensing means includes means responsive to said pilot signal for generating said first signal.
Claim 5
Dependent Claim
25 words
The combination of claim 3 wherein: said IF sensing means includes filter means for passing signals at said intermediate frequency and substantially attenuating other frequencies.
Claim 6
Dependent Claim
28 words
The combination of claim 4 wherein: said IF sensing means includes peak detecting means for peak detecting the output of said filter means and providing said second signal.
Claim 7
Dependent Claim
46 words
The combination of claim 1 including: AFC means for applying automatic frequency control signals from said detecting stage to said tuning stage in response to said third signal, with said tuning stages being fine tuned in response thereto to the tuned frequency of said stereo broadcast.
Claim 8
Dependent Claim
80 words
The combination of claim 5 wherein said stereo sensing means includes: pilot amplifying means responsive to said 19 kHz. pilot signal for providing an amplified pilot output; doubler means responsive to said amplifier pilot output for providing said first signal as detected 38 kHz. signals and also providing demodulating 38 kHz. signals; and including stereo demodulating means responsive to the output of said detecting stage and said demodulating 38 kHz. signals for providing the stereo audio outputs of said receiver.