Circuit arrangement for automatic frequency control in a radio t

Details Circuit arrangement for automatic frequency control in a radio t Circuit arrangement for automatic frequency control in a radio t

1992-02-21

1994-08-02

Eisenzopf, Reinhard J.

Telecommunications

Transmitter and receiver at same station

With frequency stabilization

4551822, 4551922, 455264, 455265, H04B 140, H04B 116

Patent

active

053353641

ABSTRACT:
The present invention relates to a circuit arrangement by which a voltage-controlled temperature-compensated oscillator (VCTCXO) (10) serving as the frequency reference in a radio telephone is controlled. In the circuit arrangement there is used a phase-locked loop which locks the frequency of the VCTCXO (10) to the frequency of the intermediate-frequency signal (2.IF) of the receiver of the telephone. When the telephone is started up, a constant setting voltage (30) is coupled as the control signal (V.sub.con) for the VCTXCO (10) for controlling the reference frequency. In the call state the control signal (V.sub.con) is provided by by the phase-locked loop in which the locking is to the frequency of the intermediate frequency signal. When the call is cut off the control voltage (V.sub.con) is supplied from a memory (26) coupled to the phase-locked loop in which the value of the control signal (V.sub.con) is substantially equal to the control signal (V.sub.con) supplied by the phase-locked loop at the moment of cut-off, and which has been stored in the memory (26).

REFERENCES:
patent: 4817197 (1989-03-01), Shimizu et al.
patent: 4932072 (1990-06-01), Toko
patent: 5073973 (1991-12-01), Ylivakeri
patent: 5115515 (1992-05-01), Yamamoto et al.
patent: 5170492 (1992-12-01), Moller et al.

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