Parametrically driven quartz UHF oscillator
The present invention is a piezoelectric crystal oscillator using parametric amplification to enhance the Q. Parametric amplification is accomplished by driving the same region of the crystal as used for the oscillator with an overtone of the crystal resonator.
1. An oscillator device comprising:
a slab of piezoelectric material with a first frequency of a mechanical mode of vibration;
a first drive electrode disposed on an upper surface of the slab and a second drive electrode disposed on a lower surface of the slab opposite the first drive electrode;
a first amplifier operating at substantially an integer multiple of the first frequency;
an input of a second amplifier connected to the first drive electrode and an output of the second amplifier connected to an input of the first amplifier;
the second drive electrode connected to the sum of an output of the first amplifier and the output of the second amplifier.
2. The oscillator of claim 1 wherein the first amplifier operates substantially at twice the first frequency.
3. The oscillator of claim 1 wherein the first amplifier comprises:
a bandpass filter with a center frequency substantially equal to the first frequency;
an output of the bandpass filter is connected to an input of a frequency multiplier; and
the frequency multiplier configured to generate an output at a multiple of the first frequency;
wherein the input of the first amplifier is connected to an input of the bandpass filter.
4. The oscillator of claim 3 wherein the first amplifier further comprises a phase shifter connected to the output of the frequency multiplier;
wherein the output of the phase shifter is connected to the output of the first amplifier.
5. The oscillator of claim 1 wherein the piezoelectric material is selected from the group consisting of quartz, langasite, langanite and langatate.
6. The oscillator of claim 1 wherein the piezoelectric material is selected from the group comprising an AT-cut quartz and a SC-cut quartz.
7. The oscillator of claim 1 wherein the mode of mechanical vibration is a shear mode.
8. The oscillator of claim 7 wherein the first frequency of a mechanical mode of vibration is greater than 50 MHz.
9. The oscillator of claim 1 wherein the bandpass filter is an integrated monolithic crystal filter formed on the slab of piezoelectric material.
10. The oscillator of claim 3 wherein the bandpass filter comprises electrodes disposed on the slab near the first drive electrode and second drive electrode.
11. A piezoelectric resonator configured for parametric amplification, said piezoelectric resonator comprising:
a piezoelectric member;
a first and second resonator electrodes associated with said piezoelectric member and positioned to enable a first electric field to be generated in a first direction; and first and second parametric drive electrodes associated with said piezoelectric member and positioned to enable a second electric field to be generated in said first direction and coincident with said first electric field.
12. The piezoelectric resonator of claim 11 wherein the resonator has a resonant frequency equal to a frequency of a mechanical mode of vibration; and
the first electric field oscillates at the frequency of the mechanical mode of vibration; and
the second electric field oscillates at a frequency a multiple of the frequency of the mechanical mode of vibration.
13. An oscillator device comprising:
a slab of piezoelectric material with a first frequency of a mechanical mode of vibration;
a first means for driving the piezoelectric material at the first frequency; and
a second means for driving the piezoelectric material at an integer multiple of the first frequency
wherein the second means for driving the piezoelectric material further comprises means for receiving an output of the first means for driving the piezoelectric material;
means for bandpass filtering the output of the first means for driving the piezoelectric material;
means for frequency multiplying an output of the bandpass filter by the integer number; and
means for phase shifting an output of the means for frequency multiplying.
14. The oscillator of claim 13 wherein the integer multiple is two.
15. The oscillator of claim 13 wherein the piezoelectric material is selected from the group consisting of quartz, langasite, langanite and langatate.
16. The oscillator of claim 13 wherein the piezoelectric material is selected from the group comprising an AT-cut quartz and a SC-cut quartz.
17. The oscillator of claim 13 wherein the mode of mechanical vibration is a shear mode.
18. The oscillator of claim 13 wherein the first frequency of a mechanical mode of vibration is greater than 50 MHz.