Frequency synthesizer

Claim 2

In a frequency synthesizer a sweep search frequency acquisition means effective during an acquisition mode comprising: a sequencer including a counter means; a phase locked loop including a voltage controlled oscillator whose output frequency is dependent upon an applied voltage; a harmonic reference frequency generator for selectably generating one reference frequency harmonic group out of a plurality of such groups in response to the state of said sequencer; means for mixing the phase locked loop output frequency with the selected reference frequency harmonic group to thereby generate counter signals, said counter signals being accumulated by said counter means to vary the state of said sequencer; and, a sweep means for varying the voltage applied to said voltage controlled oscillator at least during the time said synthesizer is in said acquisition mode.

Claim 3

Acquisition means as recited in claim 1 wherein said sweep means comprises sweep speed control means responsive to the state of said sequencer for changing the rate at which said voltage is varied.

Claim 4

Acquisition means as recited in claim 2 wherein said sweep speed control means comprises: a capacitor, the voltage at which comprises said voltage; a constant current generator responsive to a selected electrical means for supplying charges to said capacitor at a rate determined by the selected electrical means; and, a plurality of said electrical means, one of said electrical means being selected in response to the state of said sequencer.

Claim 5

Acquisition means as recited in claim 3 with additionally means for generating a start signal, said sweep speed control means being responsive to said start signal for discharging the voltage at said capacitor to a predetermined base voltage.

Claim 6

Acquisition means as recited in claim 1 wherein said means for mixing includes first detector means for generating counter signals when said output frequency sweeps past one harmonic of the instantaneously selected harmonic group and second detector means for generating counter signals when said output frequency sweeps past the intermediate point between adjacent harmonics of the instantaneously selected harmonic group.

Claim 7

In a frequency synthesizer having a phase locked loop for generating an output frequency including means for sweeping said output frequency during a search mode, a hormonic frequency generator for generating harmonic reference frequencies at a predetermined channel spacing and a mixer means for detecting the nulls obtained when said output frequency is mixed with said harmonic reference frequencies, said nulls being counted until a preselected number corresponding to a desired synthesizer output frequency is counted at which time the search mode is terminated and the phase locked loop locks at the desired synthesizer output frequency, an improvement comprising: null detector means for generating a first signal when said output frequency as swept passes one of said harmonic reference frequencies; intermediate detector means for generating a second signal when said output frequency as swept passes the approximate midpoint between two said harmonic reference frequencies; counter means for accumulating said first and second signals; and, gating means responsive to the instantaneous state of said counter means for directing said first and second signals to said counter means and for controlling the rate at which said output frequency is swept during said search mode.

Claim 8

In a frequency synthesizer having a phase locked loop for generating an output frequency including means for sweeping said output frequency during a search mode, a hormonic frequency generator for generating harmonic reference frequencies at a predetermined channel spacing and a mixer means for detecting the nulls obtained when said output frequency is mixed with said harmonic reference frequencies, said nulls being counted until a preselected number corresponding to a desired synthesizer output frequency is counted at which time the search mode is terminated and the phase locked loop locks at the desired synthesizer output frequency, an improvement comprising: null detector means for generating a first signal when said output frequency as swept passes one of said harmonic reference frequencies; intermediate detector means for generating a second signal when said output frequency as swept passes the approximate midpoint between two said harmonic reference frequencies; counter means for accumulating said first and second signals; and, gating means responsive to the instantaneous state of said counter means for directing said first and second signals to said counter means and for controlling the rate at which said output frequency is swept during said search mode.

Claim 9

The improvement of claim 6 wherein said gating means includes means responsive to the instantaneous state of said counter means for extinguishing said harmonic reference frequencies and for generating a different group of harmonic reference frequencies, said null detector means and said intermediate detector means being responsive to said different group when generated.

Claim 10

A frequency synthesizer comprising: means for generating a plurality of reference frequency signals at decade intervals; means responsive to control signals for selecting one of said plurality of reference frequency signals; a spectrum generator for generating the harmonics of the selected reference frequency signal; a voltage controlled oscillator responsive to an applied voltage signal for generating an output frequency; mixer means responsive to the harmonics of the selected reference frequency signal and said output signal for generating a first signal when said output signal sweeps through one of said harmonics and for generating a second signal when said output frequency sweeps through a point intermediate adjacent ones of said harmonics; first detector means for generating counter signals in response to said first signals when the speed at which said output frequency is swept is within a predetermined rate; second detector means for generating counter signals in response to said second signals; counter means for accumulating said counter signals; gate means responsive to the instantaneous state of said counter means for generating said control signals; and, means responsive to said control signals for controlling the rate of change of said voltage signal.

Claim 11

A frequency synthesizer comprising: means for generating a plurality of reference frequency signals at decade intervals; means responsive to control signals for selecting one of said plurality of reference frequency signals; a spectrum generator for generating the harmonics of the selected reference frequency signal; a voltage controlled oscillator responsive to an applied voltage signal for generating an output frequency; mixer means responsive to the harmonics of the selected reference frequency signal and said output signal for generating a first signal when said output signal sweeps through one of said harmonics and for generating a second signal when said output frequency sweeps through a point intermediate adjacent ones of said harmonics; first detector means for generating counter signals in response to said first signals when the speed at which said output frequency is swept is within a predetermined rate; second detector means for generating counter signals in response to said second signals; counter means for accumulating said counter signals; gate means responsive to the instantaneous state of said counter means for generating said control signals; and, means responsive to said control signals for controlling the rate of change of said voltage signal.

Claim 12

The frequency synthesizer of claim 8 wherein said first detector means comprises a plurality of null detectors, each associated with only one of said reference frequency signals and generating counter signals when said output frequency sweeps through the harmonics of its associated reference signal, and wherein said second detector means comprises a plurality of intermediate detectors, each associated with only one of said reference frequency signals and generating counter signals when said output frequency sweeps through a point intermediate adjacent ones of the harmonics of its associated reference frequency signal.

Claim 13

The frequency synthesizer of claim 9 wherein said counter means comprises a plurality of counters, each said counter associated with a different one of said reference frequency signals and with additionally a plurality of selectors, one associated with each said counter and for entering a binary number into the associated counter, the binary number so entered being related to a portion of a desired synthesizer output frequency.

Claim 14

The frequency synthesizer of claim 10 with additionally means for generating a start signal, said counter means being responsive to said start signal for acquiring a number related to a desired synthesizer output frequency and for driving said voltage signal to a base value whereby said output frequency is driven to a base frequency.

Claim 15

The frequency synthesizer of claim 11 wherein said means for generating a start signal in response to any one of a plurality of conditions indicative of said synthesizer output frequency not being at a desired value.