Methods and apparatus for tuning devices having resonators

Abstract

Methods and apparatus for tuning devices having resonators are described. Phase shifters are included in the circuits and used to shift the phase of the output signal(s) of the resonators. In some implementations, the phase shifters are configured in a feedback loop with the resonators. One or more of the apparatus described herein may be implemented as part, or all, of a microelectromechanical system (MEMS).

What is claimed is: 
     
         1 . A method of tuning a device having a mechanical resonator, the method comprising:
 receiving an output signal of the mechanical resonator;   producing a phase-shifted signal from the output signal; and   inputting the phase-shifted signal to the mechanical resonator.   
     
     
         2 . The method of  claim 1 , wherein producing the phase-shifted signal is performed without using a variable capacitor. 
     
     
         3 . The method of  claim 2 , wherein producing the phase-shifted signal is performed without using a varactor. 
     
     
         4 . The method of  claim 2 , wherein producing the phase-shifted signal is performed without using an inductor. 
     
     
         5 . The method of  claim 1 , wherein producing the phase-shifted signal comprises generating, from the output signal, a first signal and a second signal and phase shifting the first signal relative to the second signal. 
     
     
         6 . The method of  claim 5 , wherein producing the phase-shifted signal further comprises amplitude weighting the first signal and second signal by different amounts. 
     
     
         7 . The method of  claim 6 , wherein producing the phase-shifted signal further comprises combining the first signal and second signal subsequent to phase-shifting the first signal relative to the second signal and amplitude weighting the first signal and second signal by different amounts. 
     
     
         8 . The method of  claim 7 , wherein combining the first signal and the second signal comprises adding the first signal and the second signal together. 
     
     
         9 . The method of  claim 7 , wherein producing the phase-shifted signal further comprises limiting an amplitude of at least one of the first signal and the second signal. 
     
     
         10 . The method of  claim 9 , wherein limiting an amplitude of at least one of the first signal and the second signal comprises limiting the amplitude by an amount configured to provide a feedback loop comprising the mechanical resonator with unity gain. 
     
     
         11 . The method of  claim 6 , wherein amplitude weighting the first signal and second signal by different amounts comprises applying unity gain to one of the first signal and second signal. 
     
     
         12 . The method of  claim 5 , wherein phase-shifting the first signal relative to the second signal comprises phase shifting only one of the first signal and second signal. 
     
     
         13 . The method of  claim 5 , wherein generating the first signal and the second signal comprises splitting the output signal. 
     
     
         14 . The method of  claim 1 , wherein the output signal of the mechanical resonator is a multi-ended signal comprising a first end and a second end and wherein producing the phase-shifted signal comprises phase-shifting the first end relative to the second end. 
     
     
         15 . The method of  claim 14 , wherein phase-shifting the first end relative to the second end comprises phase-shifting the first end by a first amount and phase shifting the second end by a second amount. 
     
     
         16 . The method of  claim 14 , wherein producing the phase-shifted signal further comprises amplitude weighting the first end and second end by different amounts. 
     
     
         17 . The method of  claim 16 , wherein phase-shifting the first end relative to the second end is performed prior to amplitude weighting the first end and second end by different amounts. 
     
     
         18 . The method of  claim 16 , wherein amplitude weighting the first end and second end by different amounts is performed prior to phase-shifting the first end relative to the second end. 
     
     
         19 . The method of  claim 16 , wherein producing the output signal further comprises limiting an amplitude of at least one of the first end and the second end. 
     
     
         20 . The method of  claim 14 , wherein producing the phase-shifted signal further comprises adding signals resulting from phase-shifting the first end relative to the second end using a differential summation circuit.