Direct digital synthesizer with a central frequency controllable

Details Direct digital synthesizer with a central frequency controllable Direct digital synthesizer with a central frequency controllable

1992-12-29

1995-04-18

Eisenzopf, Reinhard J.

Telecommunications

Transmitter and receiver at same station

With frequency stabilization

455260, 455310, 331 18, 331 25, H03L 718, H04B 140

Patent

active

054086876

ABSTRACT:
A synthesizer for use in a transmitter/receiver effectively eliminates spurious signals contained in an output signal. The synthesizer has a direct digital synthesizer for producing an output signal having a frequency corresponding to oscillation frequency data, and a voltage-controlled variable bandpass filter to which the output signal from the direct digital synthesizer is supplied. The oscillation frequency data is also supplied to a ROM, from which control voltage data corresponding to the supplied oscillation frequency data is read. The control voltage data from the ROM is supplied to a D/A converter which applies a control voltage to the voltage-controlled variable bandpass filter. The center frequency of the passband of the voltage-controlled variable bandpass filter is controlled by the applied control voltage in conformity with the frequency of the output signal from the direct digital synthesizer. The output signal from the direct digital synthesizer passes through a narrow passband of the voltage-controlled variable bandpass filter, so that spurious signals are eliminated from the output signal from the direct digital synthesizer.

REFERENCES:
patent: 4951004 (1990-08-01), Sheffer et al.
patent: 4965533 (1990-10-01), Gilmore
patent: 5028887 (1991-07-01), Gilmore
patent: 5130671 (1992-07-01), Shahriary et al.

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