Circuitry for the diversity unit in an FM receiver for a telepho

Details Circuitry for the diversity unit in an FM receiver for a telepho Circuitry for the diversity unit in an FM receiver for a telepho

1987-11-10

1989-08-08

Griffin, Robert L.

Telecommunications

Receiver or analog modulated signal frequency converter

Plural receivers

455 52, 455137, 455276, H04B 1116

Patent

active

048560804

ABSTRACT:
A circuitry in a diversity unit of an FM receiver for a telephone system having at least two channels for receiving signals, and at least one phase-lock loop. The signals received by the channels which possibly differ from each in amplitude and frequency. Each channel comprises a mixer and a band-pass filter for forming an intermediate-frequency signal. The phase-lock loop has phase-lock branches operably connected between each mixer of the channels which comprises a frequency-phase comparator. The phase-lock loop equalizes the channel signals in phase and amplitude. The phase-lock loop further has a summation circuit for adding the channel signals which have been equalized. The frequency-phase comparator has a single phase-lock branch exiting therefrom along with a voltage-controlled oscillator connected to one of the mixers of one of the channels. The voltage-controlled oscillator has a switch on an input side thereof. The switch are for disconnecting the input side of the voltage-controlled oscillator from the frequency-phase comparator of the single phase-lock branch and for switching the voltage-controlled oscillator to a fixed and preset reference frequency. Coupled to another of one of the mixers of another set channels is a fixed-frequency oscillator and a signal-level sensing circuit which, in an event of slow fading the other channel, inputs a separate signal to the switch means of the voltage-controlled oscillator in order to switch the voltage-controlled oscillator to the fixed reference frequency.

REFERENCES:
patent: 4386435 (1983-05-01), Ulmer et al.
patent: 4406017 (1983-04-01), Takahashi
patent: 4528697 (1985-07-01), Nichols
patent: 4584712 (1986-04-01), Isobe et al.
patent: 4593413 (1986-06-01), Ozaki
patent: 4700366 (1987-10-01), Henriksson
patent: 4731801 (1988-03-01), Henriksson
patent: 4752941 (1988-06-01), Takahara et al.

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