Apparatus for measuring frequency change of an oscillator

1. A method, comprising:

scaling a first output signal from a first oscillator to provide a first output frequency from a first frequency synthesizer, the first oscillator comprising a first resonator having a first resonant frequency, wherein the first resonant frequency is temperature dependent;

scaling a second output signal from a second oscillator to provide a second output frequency from a second frequency synthesizer, the second oscillator comprising a second resonator having a second resonant frequency, wherein the second resonant frequency is temperature dependent;

mixing the first output frequency with the second output frequency to determine a difference frequency;

determining a change of an output frequency of the first oscillator from the difference frequency; and

determining a change in a temperature from the output frequency.

2. The method of claim 1 , wherein the difference frequency is at least four orders of magnitude less than the first output frequency and the second output frequency.

3. The method of claim 1 , wherein the determining comprises:

measuring a period of an output signal after the mixing; converting the period into the difference frequency; and determining the change in the output frequency from the difference frequency.

4. An apparatus, comprising:

a first oscillator, the first oscillator comprising a first resonator having a first resonant frequency, wherein the first resonant frequency is temperature dependent;

a second oscillator, the second oscillator comprising a second resonator having a second resonant frequency, wherein the second resonant frequency is temperature dependent;

a first frequency synthesizer configured to receive a first input from the first oscillator and to provide a scaled first output frequency based on the first input;

a second frequency synthesizer configured to receive a second input from the second oscillator and to provide a scaled second output frequency based on the second input;

a mixer configured to receive the scaled first output frequency and the scaled second output frequency and to output a difference between the scaled first output frequency and the scaled second output frequency; and

a processor configured to determine a change in an output frequency of the first oscillator based on the difference, and to determine a temperature of the first resonator from the output frequency.

5. The apparatus of claim 4 , wherein a frequency of the difference is at least four orders of magnitude less than the first output frequency and the second output frequency.

6. The apparatus of claim 4 , wherein the first and second resonators are one of: a quartz resonator, a surface acoustic wave (SAW) resonator, and a bulk acoustic wave (BAW) resonator.

7. The apparatus of claim 4 , wherein the processor is configured to measure a period of the output from the mixer, to convert the period into a difference frequency, and to determine the change in the output frequency of the first oscillator from the difference frequency.

8. The apparatus of claim 4 , wherein the apparatus is included in a thermometer.

9. The apparatus of claim 4 , wherein the apparatus is included in an infra-red imaging device.

10. An apparatus, comprising:

a first substrate comprising a reaction site;

a second substrate comprising a first resonator and a second resonator, wherein the first resonator is thermally coupled to the reaction site, the first oscillator comprising a first resonator having a first resonant frequency, wherein the first resonant frequency is temperature dependent, and the second oscillator comprising a second resonator having a second resonant frequency, wherein the second resonant frequency is temperature dependent;

a first oscillator including the first resonator and a second oscillator including the second oscillator;

a first frequency synthesizer configured to receive a first input from the first oscillator and to provide a scaled first output frequency based on the first input;

a second frequency synthesizer configured to receive a second input from the second oscillator and to provide a scaled second output frequency based on the second input;

a mixer configured to receive the scaled first output frequency and the scaled second output frequency and to output a difference between the scaled first output frequency and the scaled second output frequency; and

a processor configured to determine a change in an output frequency of the first oscillator based on the difference, and to determine a temperature from the output frequency of the first oscillator.

11. The apparatus of claim 10 , wherein the first and second resonators are one of: a quartz resonator, a surface acoustic wave (SAW) resonator, and a bulk acoustic wave (BAW) resonator.

12. The apparatus of claim 10 , wherein the processor is configured to measure a period of the output from the mixer, convert the period into a difference frequency, and determine the change in the output frequency of the first oscillator from the difference frequency.