Synchronous modulation resonator with sigma delta modulator
A Synchronous Modulation Resonator (SMR) device, the device includes a resonator having coupled to a Vd source and a Vr source, wherein the Vd is DC biased, wherein the Vr is AC, wherein the resonator provides a resonator output in response to Vd and Vr, a Sigma Delta Modulator (SDM) coupled to the resonator and to the Vr source, wherein the SDM provides a signal output in response to the resonator output and to the Vr, and a digital output block coupled to the SDM, wherein the digital output block is configured to provide a digital signal representation of the resonator output, in response to the signal output.
1. A Synchronous Modulation Resonator (SMR) device, the device comprising:
a resonator having a first input coupled to a Vd driving voltage source and a Vr resonator biasing voltage source, wherein the Vd driving voltage source is characterized as DC biased, wherein the Vr resonator biasing voltage source is characterized as AC biased, wherein the resonator is configured to provide a resonator output in response to Vd from the Vd driving voltage source and Vr from the Vr resonator biasing voltage source;
a Sigma Delta Modulator (SDM) coupled to the resonator, wherein the SDM is coupled to the Vr resonator biasing voltage source, and wherein the SDM is configured to provide a signal output in response to the resonator output and to the Vr of the Vr resonator biasing voltage source; and
a digital output block coupled to the SDM, wherein the digital output block is configured to provide a digital signal representation of the resonator output, in response to the signal output.
2. The device of claim 1 wherein the signal output of the SDM being is synchronized with the resonator output of the resonator.
3. The device of claim 1 wherein the Vr resonator biasing voltage source is configured to output the Vr characterized by a duty-cycle modulation (DCM).
4. The device of claim 3 wherein DCM characterization is characterized by a product of oversampling rate (OSR)*sinc filter order (SFO) cycles.
5. The device of claim 1 being configured for a production test mode to determine resonator mechanical resonant frequency (Fm) and quality factor (Q).
6. The device of claim 1 being configured for low signal bandwidth (BW) operation of <1 kHz.
7. The device of claim 1 wherein the resonator comprises a MEMS device.
8. The device of claim 6 wherein the MEMS device is selected from a group consisting of: an accelerometer and a gyroscope.
9. The device of claim 1 wherein the Vr is characterized by a first frequency and a second frequency, wherein the first frequency comprises a resonator biasing voltage frequency associated with the resonator, and wherein the second frequency comprising a SDM sampling frequency associated with the SDM.
10. The device of claim 9 wherein the first frequency and the second frequency are different within a range of about two to about three orders of magnitudes.
11. A method for operating a Synchronous Modulation Resonator (SMR) device, the method comprising:
providing an SMR comprising
a resonator having a first input coupled to a Vd driving voltage source and a second input coupled to a Vr resonator biasing voltage source, wherein a Vd of the Vd driving voltage source being characterized as DC biased, and wherein the Vr of the Vr resonator biasing voltage source is characterized as AC biased, and wherein the resonator provides a resonator output,
a Sigma Delta Modulator (SDM) coupled to the resonator and to the Vr resonator biasing voltage source, wherein the SDM is configured to output a signal output in response to the resonator output and to the Vr, and
a digital output coupled to the SDM, wherein the digital output is configured is configured to provide a digital signal representation of the resonator output,
in response to the signal output;
modifying a frequency Fr of the Vr of the Vr resonator biasing voltage within a frequency sweep region; and
determining a resonator mechanical resonant frequency (Fm) in response to the digital signal representation of the resonator output.
12. The method of claim 10 further comprising determining a quality factor (Q) associated with the resonator, in response to the digital signal representation of the resonator output.
13. The method of claim 10 further comprising:
driving the SDM with the Vr of the Vr resonator biasing voltage; and
driving the resonator with the Vr of the Vr resonator biasing voltage.
14. The method of claim 11 wherein the Vr of the Vr resonator biasing voltage is characterized as duty-cycle modulated (DCM).
15. The method of claim 14 wherein the DCM characterization includes oversampling rate (OSR)*sinc filter order (SFO) cycles.
16. The method of claim 8 wherein determining the resonator mechanical resonant frequency (Fm) comprises maintaining Fr when the digital signal representation of the resonator output provides an output peak.
17. The method of claim 11 wherein determining the resonator mechanical resonant frequency (Fm) comprises slowly modifying the Fr when the digital signal representation of the resonator output increases.
18. The method of claim 11 further comprising in the Vr resonator biasing voltage source combining a signal comprising the resonator biasing voltage frequency and a signal comprising the SDM sampling frequency.
19. The method of claim 18 wherein the first frequency and the second frequency are different within a range of about two to about three orders of magnitudes.
20. The method of claim 11 wherein modifying the frequency Fr of the Vr comprises modifying the resonator biasing voltage frequency while maintaining the SDM sampling frequency.