A parallel-class thermally-actuated micromechanical filter with tunable center frequency and bandwidth

A thermally-actuated micromechanical filter with center frequency at very high frequency (VHF) range (64MHz) has been demonstrated for the first time by electrically coupling two thermal-piezoresistive (thermal actuation and piezoresistive readout) resonators. A small-signal equivalent circuit for this filter is proposed and used to analyze the measured frequency response. The filter exhibits tunability in the center frequency (72.2ppm) and relative bandwidth (0.002% to 0.004%) through the capability to tune the resonant frequency of each resonator by adjusting their bias voltages due to the Joule heating effect. Although the filter is not an optimized one, it is sufficient to achieve an out-of-band rejection of more than 10dB and ripple of less than ldB in the pass band throughout the whole tuning range.