US 4,791,377 AGranted

Direct frequency synthesizer

AssigneeGTE Government Systems Corporation

InventorsJohn Grandfield, James T. Campbell, Carl H. Gundel, William Shillue

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Abstract

A frequency synthesizer has in series a digital synthesizer, mix and divide circuits, and a mix only circuit. Each mix and divide circuit includes a mixer having an IF input, a LO input and a RF output, a filter, and a frequency divider. A segment of a digital word selects a tone from a tone generator and also selects a passband of the filter. The selected tone is coupled to the LO input of the mixer. The frequency divider divides the filtered RF output of the mixer. The mix only circuit is at the output of the last of the series connected mix and divide circuits. The mix only circuit is similar to a mix and divide circuit, but does not have a frequency divider. The digital synthesizer provides a signal to the input of the first of the series connected mix and divide circuits, the frequency of which corresponds to a segment of a digital word. The filter is preferably a voltage tunable bandpass filter.

Claims3

Dependent claims

A frequency synthesizer comprising:

a. tone generating means for providing a plurality of tones;
b. a plurality of series connected mix and divide circuits, including a first and a last mix and divide circuit, each mix and divide circuit including a mixer having an IF input, an LO input and a RF output, filter means for filtering the RF output of said mixer with a selectable passband;
means for selecting a tone from said tone generating means and selecting a passband of said filter means in response to a segment of a digital word;
means for coupling the selected tone to the IF input of said mixer, and frequency divider means for dividing the filtered RF output of said mixer;
c. a mix only circuit at the output of the last of said series connected mix and divide circuits, said mix only circuit including a mixer having an IF input, a LO input and a RF output, filter means for filtering the RF output of said mixer with a selectable passband, means for selecting a tone from said tone generating means and selecting a passband of said filter means in response to a segment of a digital word;
means for coupling the selected tone to the IF input of said mixer, and
d. a digital synthesizer for providing a signal to the input of the first of said series connected mix and divide circuits, the frequency of said signal corresponding to a segment of a digital word.

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/110,396Filed 20 Oct 1987
Granted: 13 Dec 1988
Term ends: Not estimatedThe source records don’t support an estimate.

Classification4 codes

H03B 21/04
By beating unmodulated signals of different frequencies: using several similar stages
H03B 21/025
By plural beating, i.e. for frequency synthesis ; Beating in combination with multiplication or division of frequency: by repeated mixing in…
H03B 2200/0072
Functional aspects of oscillators: frequency hopping and enabling of rapid frequency changes
H03B
Generation of oscillations, directly or by frequency-changing, by circuits employing active elements