Wide range drift compensated FM signal generator
AssigneeRCA Corporation
InventorJack E. James
Life of this patent
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Abstract
The output frequency of a variable frequency oscillator is compared with that of a reference frequency source by means of a phase detector and the resultant error signal is integrated and applied as a negative feedback signal to the input of the oscillator whereby drift of the oscillator output frequency is minimized. Deviation, modulation index, dynamic stability and linearity are enhanced by means of a pulse generator that is synchronized with a modulating input signal supplied to the oscillator for supplying a keying signal to the phase detector during a portion of each cycle of the modulating input signal.
Claims11
An improved FM signal generator comprising a variable frequency oscillator means for producing an output signal having a frequency proportional to the amplitude of a modulating input signal and a drift compensation circuit responsive to a reference frequency signal for regulating the frequency of said oscillator means, the improvement wherein said drift compensation circuit comprises:
- keyed phase detector means responsive to a keying signal supplied thereto for comparing the output frequency of said oscillator means with that of said reference signal and producing an error signal;
- means for integrating said error signal and applying the resultant integrated error signal as a negative feedback signal to said oscillator means;
- and
- pulse generator means synchronized with said modulating input signal for supplying said keying signal to said keyed phase detector means.
An FM signal generator comprising, in combination:
- controlled oscillator means responsive to a control signal supplied thereto for producing an FM output signal having a frequency proportional to said control signal;
- keyed phase detector means having a first input for receiving said FM output signal, a second input for receiving a reference signal of predetermined frequency, a third input for receiving a keying signal and an output for producing an error signal representative of the phase/frequency relationship of said FM output signal and said reference signal when said keying signal is present;
- memory means for accumulating said error signal during the period said keyed phase detector is enabled by the presence of said keying signal and for storing said error signal during the period said keyed phase detector is not enabled;
- means for combining a modulating input signal with the accumulated and stored error signal in said memory means and for applying the resultant signal as said control signal to said controlled oscillator means;
- and
- pulse generator means synchronized with said modulating input signal for supplying said keying signal to said keyed phase detector means at least once during each period of said modulating input signal.
Dependencies are inferred from the claim text.