Micromechanical resonator based bandpass sigma-delta modulator

Abstract

The design of a newly proposed 2nd-order bandpass I#I? modulator based on micromechanical resonator is presented. The micromechanical resonator is used to replace its electronic counterpart for its high Q value. The design is based on pulse-invariant transform and multi-feedback technique. The proposed modulator is implemented in a 0.6-I?m CMOS process with an external clamped-clamped beam micromechanical resonator.Due to the lack of qualified micromechanical resonators, the testing with the only micromechanical resonator did not give expected results. The test was subsequently carried out with crystal resonators and successfully demonstrated a 2nd-order bandpass I#I? modulator, which proves that the proposed idea is feasible. The test results have shown that when sampled at 4MHz the peak SNR in 200-kHz signal bandwidth is measured to be 22dB while the Matlab simulated value is 25dB. The modulator is also functional at the sampling frequency of 32MHz.