Closed loop variable frequency signal generator

Claim 2

A variable frequency signal generator, comprising: closed loop circuit means operable to produce a circuit output signal of controllable frequency over an output frequency range, said closed loop circuIt means including a signal generator means producing an output signal which is said circuit output signal, said signal generator including a control input for control of the frequency of said circuit output signal, said closed loop circuit means further including a first signal mixing means having first and second input; first signal source means operable to produce a stepping signal of selectively variable frequency over a first frequency range; means applying said circuit output signal to said first input of said first signal mixing means; means applying said stepping signal to said second input of said first signal mixing means, said first signal mixing means operable in response to said circuit output signal and said stepping signal to produce an output signal having sum and difference frequencies; second signal source means operable to produce an input signal of selectively variable frequency over a second frequency range; detector means in said closed loop circuit means responsive to said difference signal from said first signal mixing means and said input signal from said second signal source means for generating a control signal when said circuit output signal applied to said first signal mixing means is higher in frequency than said stepping signal applied to said first signal mixing means, and also when said circuit output signal applied to said first signal mixing means is lower in frequency than said stepping signal applied to said first signal mixing means, said closed loop circuit being stabilized when the frequency of said input signal is equal to said difference frequency; means applying said control signal to said control input of said signal generator means to adjust the output frequency of said circuit output signal, until said closed loop circuit means is stabilized, said closed loop circuit means capable of stabilizing at first and second output frequencies, respectively, with one input signal frequency and one stepping signal frequency, said first and second output frequencies being above and below, respectively, the frequency of said one stepping signal frequency by the amount of the frequency of said one input signal frequency; means for selecting a desired output frequency from said output frequency range; control means responsive to said selecting means for controlling the frequencies of said first and second signal source means, respectively, and for partially controlling the frequency of said circuit output signal such that said closed loop circuit means tends to stabilize at a selected one of said first and second output frequencies.

Claim 3

An apparatus of claim 1, wherein said control means includes logic means responsive to said selecting means for selecting one stepping signal frequency and one input signal frequency for each output frequency.

Claim 4

An apparatus of claim 1, wherein said first frequency range includes a high and a low input frequency defining a first frequency separation therebetween, and wherein a second frequency separation exists between successive frequencies in said second frequency range, said second frequency separation being no greater than said first frequency separation.

Claim 5

An apparatus of claim 1, wherein said first signal source means includes means for generating a reference frequency, and means for generating a series of harmonic frequencies of said reference frequency, and further includes selective filter means responsive to said control means for discriminating selectively between said harmonic frequencies in accordance with said desired output frequency.

Claim 6

An apparatus of claim 1, wherein each single stepping frequency is associated with first and second independent portions of said output frequency range, said first independent portion including those circuit output signals having frequencies defined by adding each input frequency in turn to said single stepping frequency, and said second portion including those circuit output signals having frequencies formed by subtraCting each input frequency in turn from said single stepping frequency.

Claim 7

An apparatus of claim 1, wherein said closed loop circuit means further includes a circuit output signal level control means, said level control means comprising means for detecting the power level of a given circuit output signal, means coupling a portion of said given circuit output signal to said power detecting means, means for attenuating the power level of said given circuit output signal, means responsive to said power detecting means for comparing the detected power level of said given circuit output signal with a desired power level, and means controlling said attenuating means so as to maintain the power level of said given circuit output signal at said desired power level.

Claim 8

An apparatus of claim 1, wherein each output frequency has associated therewith a preselected stepping frequency, said control means including means producing first and second control output signals, and means applying said first and second control output signals to said signal generator means, said producing means producing said first control output signal when a selected circuit output signal is higher in frequency than its associated stepping signal and producing said second control output signal when said selected circuit output signal is lower in frequency than its associated stepping signal.

Claim 9

An apparatus of claim 2, wherein said control means includes memory means for storing information representative of the one stepping frequency associated with each output frequency.

Claim 10

An apparatus of claim 1, including frequency divider means connected between said first signal mixing means and said detector means.

Claim 11

An apparatus of claim 1, including a second signal mixing means having two inputs and an output and a third signal source means and including means connecting said third signal source means to one input of said second signal mixing means, means applying said circuit output signals to said other input of said second signal mixing means, and means connecting the output of said second signal mixing means to said one input of said first signal mixing means.

Claim 12

A frequency synthesizer, comprising: a phase locked loop comprising in series connection a voltage controlled oscillator, a first signal mixing means having first and second inputs, and a phase detector having first and second inputs, wherein said voltage controlled oscillator is operable under control of said phase detector to produce circuit output signal having an output frequency controllable over an output frequency range; first signal source means operable to produce a stepping signal having a stepping frequency; means applying said stepping signal to said first input of said first signal mixing means, said first signal mixing means being responsive to said stepping signal at the first input thereof and to said circuit output signal at the second input thereof to generate an output signal having sum and difference frequencies; second signal source means operable to produce an input signal having an input frequency; means for selecting a desired output frequency, each output frequency having associated therewith one input signal frequency and one stepping signal frequency; means applying said input signal to said first input of said phase detector, said phase detector being responsive to an input signal at its first input and to a difference frequency from said first signal mixing means at its second input to generate a control signal having a level proportional to any phase difference between said input signal and said difference frequency, said phase detector being equally responsive to a first difference frequency produced when a stepping signal applied to said first signal mixing means is higher in frequency by a given amount than a circuit output signal applied to said first signal mixing means, and to an identical difference frequency produced when a stepping signal applied to said first signal mIxing means is lower in frequency by said given amount than a circuit output signal applied to said first signal mixing means, said voltage controlled oscillator producing first and second output frequencies with one input signal frequency and one stepping signal frequency; control means responsive to said selecting means for controlling said voltage controlled oscillator in conjunction with said phase detector such that the selected one of said first and second output frequencies is produced; and an output frequency level control means connected in said phase locked loop, said level control means comprising means for detecting the power level of a given circuit output signal, means coupling a portion of said given circuit output signal to said power detecting means, means for attenuating the power level of said given circuit output signal, and means responsive to said power detecting means for comparing the detected power level of said given circuit output signal with a desired power level and controlling said attenuating means so as to maintain the power level of said given circuit output signal at said desired power level.

Claim 13

A frequency synthesizer, comprising: a phase locked loop comprising in series connection a voltage controlled oscillator, a first signal mixing means having first and second inputs, and a phase detector having first and second inputs, wherein said voltage controlled oscillator is operable under control of said phase detector to produce circuit output signal having an output frequency controllable over an output frequency range; first signal source means operable to produce a stepping signal having a stepping frequency; means applying said stepping signal to said first input of said first signal mixing means, said first signal mixing means being responsive to said stepping signal at the first input thereof and to said circuit output signal at the second input thereof to generate an output signal having sum and difference frequencies; second signal source means operable to produce an input signal having an input frequency; means for selecting a desired output frequency, each output frequency having associated therewith one input signal frequency and one stepping signal frequency; means applying said input signal to said first input of said phase detector, said phase detector being responsive to an input signal at its first input and to a difference frequency from said first signal mixing means at its second input to generate a control signal having a level proportional to any phase difference between said input signal and said difference frequency, said phase detector being equally responsive to a first difference frequency produced when a stepping signal applied to said first signal mixing means is higher in frequency by a given amount than a circuit output signal applied to said first signal mixing means, and to an identical difference frequency produced when a stepping signal applied to said first signal mIxing means is lower in frequency by said given amount than a circuit output signal applied to said first signal mixing means, said voltage controlled oscillator producing first and second output frequencies with one input signal frequency and one stepping signal frequency; control means responsive to said selecting means for controlling said voltage controlled oscillator in conjunction with said phase detector such that the selected one of said first and second output frequencies is produced; and an output frequency level control means connected in said phase locked loop, said level control means comprising means for detecting the power level of a given circuit output signal, means coupling a portion of said given circuit output signal to said power detecting means, means for attenuating the power level of said given circuit output signal, and means responsive to said power detecting means for comparing the detected power level of said given circuit output signal with a desired power level and controlling said attenuating means so as to maintain the power level of said given circuit output signal at said desired power level.

Claim 14

An apparatus of claim 11, wherein said control means includes means for producing a first control output signal when a selected output frequency is higher in frequency than its associated stepping frequency and for producing a second control output signal when a selected output frequency is lower in frequency than its associated stepping signal frequency.

Claim 15

An apparatus of claim 11, wherein said first signal source means is operable to produce a plurality of stepping signal frequencies, wherein said second signal source means is operable to produce a plurality of input signal frequencies, wherein each output frequency has associated therewith a preselected stepping frequency, and including means for generating an input control signal representative of any difference in frequency between a selected output frequency and its associated preselected stepping frequency, and means for applying said input control signal to said second signal source means, said second signal source means producing in response thereto an input signal having a frequency equal to the difference between said selected output frequency and its associated preselected stepping frequency.

Claim 16

An apparatus of claim 11, including a second signal mixing means having two inputs and an output, and a third signal source means including means connecting said third signal source means to one input of said second signal mixing means, means applying said circuit output signals to said other input of said second signal mixing means, and means connecting the output of said second signal mixing means to said one input of said first signal mixing means.