Micro-mechanical Resonator Band-pass Sigma Delta Modulator-based Modeling And Simulation

In modern RF receivers, high-speed and high-resolution ADCs are needed for IFor RF digitization. Bandpass∑△modulator is seen as a potential candidate to fulfillthis requirement. However, the speed of discrete-time bandpass∑△modulatorimplemented with switched-capacitor circuit is limited by the settling time of theopamps, while the continuous-time bandpass modulator can operate at much highsampling frequency, but suffers from the degradation of dynamic range due to thelow-Q LC or G_mC resonators.This work is to investigate the possibility of employing micromechanicalresonators in bandpass∑△modulator design. The micromechanical resonator is usedto replace its electronic counterpart for its high Q value. The design is based onpulse-invariant transform and multi-feedback technique. A compensation circuit isproposed to cancel the anti-resonance in the micromechanical resonator in order toobtain the desired transfer function. The proposed modulator is implemented in a0.6-μm CMOS process with an external clamped-clamped beam micromechanicalresonator.