A bandpass sigma-delta modulator employing micro-mechanical resonator

A new second-order bandpass sigma-delta modulator employing a micro-mechanical resonator is presented. The micro-mechanical resonator is used to replace its electronic counterpart for its high Q value. The design is based on the pulse-invariant transform and multi-feedback technique. A compensation circuit is proposed to cancel the anti-resonance in the micro-mechanical resonator in order to obtain the desired transfer function. The modulator is implemented in a 0.6 μm CMOS process with an external clamped-clamped beam micro-mechanical resonator. Simulations show that a 47 dB dynamic range can be achieved in a 200 kHz bandwidth centered at 8 MHz when sampled at 32 MHz.