Digitally controlled temperature compensated oscillator system

• US 4,380,745 A
• Filed: 11/07/1980
• Issued: 04/19/1983
• Est. Priority Date: 11/07/1980
• Status: Expired due to Term

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Barlow, Michael L., Lindstrum, Alan L.
• Primary Examiner(s): Grimm, Siegfried H.
• Application Number:
  US06/205,027
• Time in Patent Office: 893 Days
• Field of Search: 331/176, 331/66, 331/158
• US Class Current: 331/176
• CPC Class Codes: H03K 3/011 Modifications of generator to compensate for variations in physical values, e.g. voltage, temperature to maintain energy constant H03K3/015
• CPC Class Codes: H03L 1/026 by using a memory for digitally storing correction values H03L1/025 takes precedence
• CPC Class Codes: H03L 1/027 by using frequency conversion means which is variable with temperature, e.g. mixer, frequency divider, pulse add/substract logic circuit H03L1/023, H03L1/026 take precedence

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.

Claims

1. 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.

2. A system as recited in claim 1 wherein said means for converting said second output signal to a first binary number comprises:

(a) a binary counter coupled to be enabled by said second output signal and having its clock input coupled to the system output signal.

3. A system recited in claim 2 wherein said means for generating a signal having said error frequency includes:

(a) a programmable frequency divider coupled to be programmed by said second binary number from said programmable memory and having its clock input coupled to the system output signals.