Digitally controlled temperature compensated oscillator system
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorsMichael L. Barlow, Alan L. Lindstrum
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Abstract
A crystal oscillator that is temperature compensated by digitally substrang a correction frequency from the running frequency of the crystal oscillator to provide the required operating frequency. The correction frequency is generated by a digital frequency synthesizer circuit which is controlled by the output of a programmable read-only memory which has been programmed to generate the required correction frequency for each temperature code over the operating temperature range. The temperature code is generated by gating a digital counter with the output of a monostable multivibrator which utilizes a thermistor to make its gate interval proportional to temperature.
Claims3
A temperature-compensated oscillator system for producing a system output signal of a constant frequency, which comprises:
- (a) an oscillator having a known output frequency versus temperature characteristic;
- (b) a temperature sensor for producing a first output signal proportional to the temperature at which the oscillator is operating;
- (c) a temperature-controlled timer coupled to receive the first output signal, said temperature controlled timer producing a second output signal having a duration which is related to the temperature sensed by said temperature sensor;
- (d) means for converting said second output signal to a first binary number representing the temperature sensed by said temperature sensor;
- (e) a programmable memory coupled to receive said first binary number on its address input, the memory address identified by said first binary number containing a second binary number representing an error frequency to adjust the frequency of the output signal from the oscillator;
- (f) means for generating a signal having said error frequency in response to said second binary number, said means for generating coupled to receive said addressed second binary number;
- and
- (g) means for combining said signal at said error frequency with the output signal from said oscillator to produce said temperature-compensated system output signal.
Dependencies are inferred from the claim text.