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AssigneeU.S. Philips Corporation
InventorWolfdietrich G. Kasperkovitz
Estimating the term…
Radio-receiver having a frequency-locked loop which comprises, arranged one after the other, a tunable voltage-controlled oscillator, a mixer stage, a filtering element, as well as a frequency-voltage converter which is connected to the tunable voltage-controlled oscillator, several stable tunings being possible for each transmitter. An unambiguous selection is made from these stable tunings of a tuning to a desired station by muting the radio receiver in the other stable tuning frequency ranges. To this end the radio receiver according to the invention comprises a muting circuit as well as a control circuit for the muting circuit in which use is made of a further frequency voltage converter comprising an all-pass frequency-dependent 180.degree. phase shifting network, a phase detector and a limiter. By adjusting the muting circuit of the radio receiver to the quiescent condition only in the desired tuning range and by activating it outside this range, a suppression of interstation noise is obtained at the same time.
A radio receiver having a frequency-locked loop, which includes a voltage-controlled oscillator having an input for a tuning voltage, a mixer stage coupled to the voltage controlled oscillator and connected to an aerial input, a filtering element coupled to the mixer stage and a frequency-voltage converter coupled to the tuning voltage input of the voltage-controlled oscillator, characterized in that an output of the filtering element is coupled to a first input of a phase detector and, via an all-pass frequency-dependent 180.degree. phase shifting network also to a second input of the phase detector, said all-pass frequency-dependent 180.degree. phase shifting network shifting the phase of a signal passing there-through by an amount which depends on the frequency of said signal and is 180.degree. for a predetermined value of said frequency, the phase-detector being coupled, by way of a limiter, to a control input of a muting circuit for blocking an audio signal unless the receiver is substantially correctly tuned to a broadcast transmission.
Dependencies are inferred from the claim text.