Active resonator system with tunable quality factor, frequency, and impedance
Active feedback is used with two electrodes of a four-electrode capacitive-gap transduced wine-glass disk resonator to enable boosting of an intrinsic resonator Q and to allow independent control of insertion loss across the two other electrodes. Two such Q-boosted resonators configured as parallel micromechanical filters may achieve a tiny 0.001% bandwidth passband centered around 61 MHz with only 2.7 dB of insertion loss, boosting the intrinsic resonator Q from 57,000, to an active Q of 670,000. The split capacitive coupling electrode design removes amplifier feedback from the signal path, allowing independent control of input-output coupling, Q, and frequency. Controllable resonator Q allows creation of narrow channel-select filters with insertion losses lower than otherwise achievable, and allows maximizing the dynamic range of a communication front-end without the need for a variable gain low noise amplifier.
1. A method of Q-boosted filtering, comprising:
(a) providing an input signal;
(b) splitting the input signal into two signals 180° out of phase;
(c) passing each of the 180° out of phase signals through a respective Q-boosted resonator; and
(d) combining each output of the Q-boosted resonators into a Q-boosted filter output;
(e) wherein each Q-boosted resonator is a microelectromechanical system (MEMS) resonator.
2. A Q-boosted resonator, comprising:
(a) a microelectromechanical system (MEMS) wine-glass resonant structure;
(b) at least four electrodes coupled to the resonant structure;
(c) wherein the resonant structure is configured to be biased by a tuning voltage relative to the electrode that is an input, the electrode that is an output, the electrode that is a feedback input, and the electrode that is a feedback output; and
(d) wherein the resonant structure has a resonant frequency that is changed by varying the tuning voltage; and
(e) an amplifier, disposed between the feedback input electrode and the feedback output electrode, that is configured to form a positive feedback loop with the resonant structure;
(f) wherein the positive feedback loop is configured to boost an intrinsic Q of the resonant structure.
3. The Q-boosted resonator of claim 2 :
(a) wherein the at least four electrodes comprise an input electrode, an output electrode, a feedback input electrode, and a feedback output electrode, each of said electrodes coupled to the resonant structure; and
(b) wherein each of said electrodes is coupled by a coupling selected from a group of couplings consisting of: capacitive and piezoelectric.
4. The Q-boosted resonator of claim 2 , wherein each amplifier comprises a transimpedance amplifier.
5. The Q-boosted resonator of claim 2 , wherein each amplifier comprises a negative-resistance amplifier.
6. The method of Q-boosted filtering of claim 1 , further comprising:
(a) controlling a resonant frequency of each Q-boosted resonator;
(b) wherein a substantially flat pass band is formed between the resonance frequencies of the two Q-boosted resonators.
7. The method of Q-boosted filtering of claim 6 , wherein each Q-boosted resonator comprises:
(a) a resonant structure; and
(b) an input electrode, the output electrode, a feedback input electrode, and a feedback output electrode, each of said electrodes capacitively coupled to the resonant structure.
8. The method of Q-boosted filtering of claim 7 , wherein controlling the resonant frequency for one of the Q-boosted resonators comprises applying a bias voltage between the resonant structure of the Q-boosted resonator and the input electrode, the output electrode, the feedback input electrode, and the feedback output electrode, each of said electrodes capacitively coupled to the resonant structure.
9. The Q-boosted resonator of claim 2 , wherein each resonant structure is selected from a group of resonators consisting of: comb-driven resonators, piezo coupled resonators, ring resonators, contour mode ring resonators, wine-glass ring resonators, Lame mode resonators, bar resonators, flexural beam resonators, membrane resonators, comb-driven flexural-mode resonators, center-supported disk resonators, surface acoustic wave (SAW) devices, bulk acoustic wave (BAW) devices, film bulk acoustic resonator (FBAR) devices, lateral overmoded bulk acoustic-wave resonator (LOBAR) devices, piezo actuated resonators, internal dielectric actuated resonators, internally-transduced resonators having a capacitive couple formed from a semiconductor junction, and combinations of the foregoing.
10. The Q-boosted resonator of claim 2 , wherein each resonant structure is supported above a substrate by one or more anchors.
11. The Q-boosted resonator of claim 10 , wherein each resonant structure tuning voltage is transmitted through one or more of the anchors.
12. A Q-boosted resonator, comprising:
(a) a micromechanical resonant structure;
(b) at least four electrodes coupled to the resonant structure;
(c) wherein the resonant structure is configured to be biased by a tuning voltage relative to the electrode that is an input, the electrode that is an output, the electrode that is a feedback input, and the electrode that is a feedback output; and
(d) wherein the resonant structure has a resonant frequency that is changed by varying the tuning voltage; and
(e) an amplifier, disposed between the feedback input electrode and the feedback output electrode, that is configured to form a positive feedback loop with the resonant structure;
(f) wherein the positive feedback loop is configured to increase or decrease an intrinsic Q of the resonant structure.
13. The Q-boosted resonator of claim 12 , wherein each amplifier comprises a negative-resistance amplifier.
14. The Q-boosted resonator of claim 12 , wherein each resonant structure is selected from a group of resonators consisting of: comb-driven resonators, piezo coupled resonators, ring resonators, contour mode ring resonators, wine-glass ring resonators, Lame mode resonators, bar resonators, flexural beam resonators, membrane resonators, comb-driven flexural-mode resonators, center-supported disk resonators, surface acoustic wave (SAW) devices, bulk acoustic wave (BAW) devices, film bulk acoustic resonator (FBAR) devices, lateral overmoded bulk acoustic-wave resonator (LOBAR) devices, piezo actuated resonators, internal dielectric actuated resonators, internally-transduced resonators having a capacitive couple formed from a semiconductor junction, and combinations of the foregoing.
15. The Q-boosted resonator of claim 12 , wherein each resonant structure is supported above a substrate by one or more anchors.
16. A Q-controlled resonator, comprising:
(a) a microelectromechanical system (MEMS) resonant structure;
(b) at least four electrodes coupled to the MEMS resonant structure;
(c) wherein the MEMS resonant structure is configured to be biased by a voltage VP relative to a ground;
(d) wherein the four electrodes comprise:
(1) an input electrode biased at V E1 relative to the ground;
(2) an output electrode biased at V E2 relative to the ground;
(3) a feedback input electrode; and
(4) a feedback output electrode;
(e) wherein the MEMS resonant structure has a resonant frequency that is changed by varying the tuning voltage V P ; and
(f) an amplifier, disposed between the feedback input electrode and the feedback output electrode, configured to form a feedback loop with the MEMS resonant structure;
(g) wherein the feedback loop is configured to either increase or decrease an intrinsic Q of the MEMS resonant structure.
17. A Q-controlled resonator, comprising:
(a) a microelectromechanical system (MEMS) resonant structure;
(b) at least four electrodes coupled to the MEMS resonant structure;
(c) wherein the four electrodes comprise:
(1) an input electrode biased at V E1 relative to the ground;
(2) an output electrode biased at V E2 relative to the ground;
(3) a feedback input electrode; and
(4) a feedback output electrode;
(d) wherein the MEMS resonant structure has a resonant frequency that is changed by varying any of the voltages V E1 and V E2 ; and
(e) an amplifier, disposed between the feedback input electrode and the feedback output electrode, configured to form a feedback loop with the MEMS resonant structure;
(f) wherein the feedback loop is configured to either increase or decrease an intrinsic Q of the MEMS resonant structure.