Variable phase amplifier circuit and method of use
A variable phase amplifier circuit is disclosed and its method of use in tuning devices having resonators. The variable phase amplifier receives an input differential signal pair. The input differential signal pair can be generated by a resonator device. The variable phase amplifier generates a modified differential signal pair in response to receiving the input differential signal pair. The variable phase amplifier provides a means to vary the phase of the modified differential signal pair with respect to the input differential signal pair, in an accurate and stable manner. If the modified differential signal pair with a phase shift introduced in it is fed back to the resonator device, the resonator will change its frequency of oscillation, where the new frequency of oscillation is a function of the phase of the modified differential signal pair.
1. A variable phase amplifier circuit comprising:
a phase splitter circuit, wherein the phase splitter circuit generates a first and a second differential signal pair in response to receiving an input differential signal pair, and wherein:
a phase of the second differential signal pair is shifted 90 degrees with respect to a phase of the first differential signal pair;
a phase of a second end of the first differential signal pair is shifted 180 degrees with respect to a phase of a first end of the first differential signal pair;
a phase of a second end of the second differential signal pair is shifted 180 degrees with respect to a phase of a first end of the second differential signal pair;
a first variable gain amplifier circuit coupled to the phase splitter circuit, wherein the first variable gain amplifier circuit comprises:
a first transistor, wherein the first transistor comprises:
a first transistor emitter node, wherein the first transistor emitter node is coupled to an adjustable current source; and
a first transistor collector node, wherein the first transistor collector node is coupled to a supply voltage through a first resistor, and wherein the first transistor collector node outputs the first end of the first scaled differential signal pair in response to the first transistor base node receiving the first end of the first differential signal pair; and
a second transistor, wherein the second transistor comprises:
a second transistor emitter node, wherein the second transistor emitter node is coupled to the first transistor emitter node; and
a second transistor collector node, wherein the second transistor collector node is coupled to the supply voltage through a second resistor, and wherein the second transistor collector node outputs the second end of the first scaled differential signal pair in response to the second transistor base node receiving the second end of the first differential signal pair;
wherein the first variable gain amplifier circuit scales the first differential signal pair by a first scale factor in response to receiving the first differential signal pair;
a second variable gain amplifier circuit coupled to the phase splitter circuit, wherein the second variable gain amplifier circuit scales the second differential signal pair by a second scale factor in response to receiving the second differential signal pair; and
a summation circuit coupled to the first and the second variable gain amplifier circuits, wherein the summation circuit receives a first and a second scaled differential signal pair from the first and the second variable gain amplifier circuits respectively, and outputs a modified differential signal pair in response;
wherein a phase of the modified differential signal pair is a function of the first scale factor, and
wherein the summation circuit sums a first end of the first scaled differential signal pair to a first end of the second scaled differential signal pair, and
wherein the summation circuit sums a second end of the first scaled differential signal pair to a second end of the second scaled differential signal pair.
2. The circuit of claim 1 , wherein the phase of the first differential signal pair is the same as a phase of the input differential signal pair.
3. The circuit of claim 1 , wherein the first differential signal pair is the input differential signal pair.
4. The circuit of claim 1 , wherein the first scale factor is different than the second scale factor.
5. The circuit of claim 4 , wherein the phase of the modified differential signal pair is a function of the first and the second scale factors.
6. The circuit of claim 1 , wherein the first variable gain amplifier circuit comprises a limiter stage, wherein the limiter stage limits the amplitude of the first scaled differential signal pair.
7. A device comprising:
a mechanical resonator; and
a variable phase amplifier circuit coupled to the mechanical resonator, wherein the variable phase amplifier circuit receives an input differential signal pair from the mechanical resonator, and wherein the variable phase amplifier circuit comprises:
a phase splitter circuit, wherein the phase splitter circuit generates a first and a second differential signal pair in response to receiving the input differential signal pair;
a first variable gain amplifier circuit, wherein the first variable gain amplifier circuit scales the first differential signal pair by a first scale factor in response to receiving the first differential signal pair from the phase splitter circuit;
a second variable gain amplifier circuit, wherein the second variable gain amplifier circuit scales the second differential signal pair by a second scale factor in response to receiving the second differential signal pair from the phase splitter circuit; and
a summation circuit, wherein the summation circuit generates a modified differential signal pair in response to receiving a first scaled differential signal pair from the first variable gain amplifier circuit and a second scaled differential signal pair from the second variable gain amplifier circuit;
wherein the mechanical resonator receives the modified differential signal pair from the variable phase amplifier, and wherein the oscillating frequency of the mechanical resonator is a function of the phase of the modified differential signal pair.
8. The circuit of claim 7 , wherein the oscillating frequency of the mechanical resonator is adjusted in response to adjusting the first scale factor.
9. The circuit of claim 7 , wherein the phase of the modified differential signal pair is adjusted in response to adjusting the first scale factor.
10. The circuit of claim 9 , wherein the summation circuit sums a first end of the first scaled differential signal pair to a first end of the second scaled differential signal pair.
11. The circuit of claim 10 , wherein the summation circuit sums a second end of the first scaled differential signal pair to a second end of the second scaled differential signal pair.
12. The circuit of claim 11 , wherein a phase of the second differential signal pair is different than a phase of the first differential signal pair.
13. The circuit of claim 12 , wherein a phase of a second end of the first differential signal pair is shifted 180 degrees with respect to a phase of a first end of the first differential signal pair.
14. The circuit of claim 13 , wherein a phase of a first end of the second differential signal pair is shifted 90 degrees with respect to a phase of the first end of the first differential signal pair.
15. A method of adjusting a phase of a differential signal pair comprising:
generating a second differential signal pair from a first differential signal pair, wherein:
a phase of the second differential signal pair is shifted 90 degrees with respect to a phase of the first differential signal pair;
a phase of a second end of the first differential signal pair is shifted 180 degrees with respect to a phase of a first end of the first differential signal pair; and
a phase of a second end of the second differential signal pair is shifted 180 degrees with respect to a phase of a first end of the second differential signal pair;
generating a first scaled differential signal pair, wherein generating a first scaled differential signal pair comprises scaling the first differential signal pair by a first scale factor;
generating a second scaled differential signal pair, wherein generating a second scaled differential signal pair comprises scaling the second differential signal pair by a second scale factor;
generating a modified differential signal pair, wherein generating a modified differential signal pair comprises summing the first and the second scaled differential signal pairs;
adjusting the second scale factor, wherein a phase of the modified differential signal pair is adjusted in response to adjusting the second scale factor;
adjusting the first scale factor, wherein the phase of the modified differential signal pair is adjusted in response to adjusting the first scale factor; and
limiting the amplitude of the first and the second differential signal pair.
16. The method of claim 15 , wherein generating a second differential signal pair from a first differential signal pair comprises phase splitting the second differential signal pair from the first differential signal pair.
17. The method of claim 15 , wherein generating a modified differential signal pair comprises:
summing together a first end of the first scaled differential signal pair and a first end of the second scaled differential signal pair; and
summing together a second end of the first scaled differential signal pair and a second end of the second scaled differential signal pair.
18. A method of adjusting the frequency of oscillation of a mechanical resonator comprising:
generating a first and a second differential signal pair in response to receiving an input differential signal pair from a mechanical resonator;
generating a first scaled differential signal pair, wherein generating a first scaled differential signal pair comprises scaling the first differential signal pair by a first scale factor;
generating a second scaled differential signal pair, wherein generating a second scaled differential signal pair comprises scaling the second differential signal pair by a second scale factor;
summing a first end of the first scaled differential signal pair and a first end of the second scaled differential signal pair together to create a first end of a summed differential signal pair;
summing a second end of the first scaled differential signal pair and a second end of the second scaled differential signal pair together to create a second end of the summed differential signal pair;
generating a modified differential signal pair, wherein generating a modified differential signal pair comprises phase shifting the first end and the second end of the summed differential signal pair by a fixed number of degrees, and wherein a phase of the modified differential signal pair is a different value than a phase of the input differential signal pair; and
providing the modified differential signal pair as input to the mechanical resonator, wherein the frequency of oscillation of the mechanical resonator is a function of the phase of the modified differential signal pair.
19. The method of claim 18 , further comprising adjusting the first scale factor, wherein the frequency of oscillation of the mechanical resonator is adjusted in response to adjusting the first scale factor.
20. The method of claim 19 , further comprising adjusting the second scale factor, wherein the frequency of oscillation of the mechanical resonator is adjusted in response to adjusting the second scale factor.
21. The method of claim 18 , wherein the phase of the first differential signal pair is shifted 90 degrees from the phase of the second differential signal pair.
22. The method of claim 21 , wherein a phase of the second end of the first differential signal pair is shifted 180 degrees from a phase of the first end of the first differential signal pair.