Frequency modulator utilizing frequency synthesizer

Details Frequency modulator utilizing frequency synthesizer Frequency modulator utilizing frequency synthesizer

1989-08-14

1991-06-25

Eisenzopf, Reinhard J.

Telecommunications

Transmitter

Angle modulation

455119, 455264, 332127, H04B 104

Patent

active

050274295

ABSTRACT:
A frequency modulator utilizing a frequency synthesizer is disclosed. The modulator is especially useful in a mobile radio communication apparatus. The synthesizer includes a phase locked loop made up of a voltage controlled oscillator (VCO), a programmable frequency divider, a phase comparator, a second frequency divider, a reference oscillator, and a low-pass filter. When a channel control signal is input to the programmable frequency divider, the modulator sensitivity of the voltage controlled oscillator is undesirably deviated according to the channel selection. An increase of the modulator sensitivity due to an increase of the oscillation frequency is compensated for by adding a simple FET to the VCO bias circuit. A control voltage from the phase locked loop is applied to both the voltage controlled oscillator and its bias circuit. The modulator can compensate for changes in sensitivity over a wider frequency bandwidth without expanding the circuit elements of the bias circuit therefore making the modulator especially useful for portable use.

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Comsat Techanical Review, A. Standing, vol. 5, No. 2, Fall 1975, pp. 355-366.

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