Design Of Band-pass Filter For Quartz Micro-gyroscope Sinusoidal Drive Circuit

Quartz micro-gyroscope is a kind of micro-inertial sensors to measure angularrate The quartz micro-gyroscope sinusoidal drive to improve the stability, resolutionand sensitivity of the detection is very important. Bandpass filter (BPF) is animportant part of the quartz micro-gyroscope sinusoidal drive circuit. In this paper, aswitched-capacitor bandpass filter and a transconductance-capacitor bandpass filteris designed. SC filter due to its high accuracy, small area has a wide range ofapplications in the fie ld of the low-frequency and is an important discrete-time filter.For continuous-time filters, OTA-C filters have often been employed since OTAsprovide high Gm’s and a good controllabilty.First we systematically studied the quartz micro-gyroscope-driven detectionprinciple and the basic filter theory in this paper. Biquad switched-capacitor filter isdesigned on the basis of switched-capacitor circuits by using Signal flow graph;According to Matlab, determined the order and the transfer function of the bandpassfilter; using the cascade method to achieve fourth-order Elliptic SC bandpass filter.Studied the transconductance amplifier (OTA) principle, by using MOS transistorwork in the linear region, combined with the Gain-the boost technology, mobilitycompensation technique to achieve a small transconductance gain, linearity fullydifferential OTA; using the OTA to achieve second-order OTA-C bandpass filter fordifferent Q value; completed system-level design of high-order band-pass filter byMatlab and a six order Butterworth OTA-C bandpass filter is designed by cascadingmethod.Using0.5μm CMOS process to design and simulate the circuit in CadenceSpectre, simulation results show that: For four order Elliptic SC BPF,the gainattenuated55.6dB in the frequency of35.4kHz; the total load capacitance is47.5pFand the capacitance distribution is27.5; by the discrete Fourier transform (DFT)the spectrum diagram shows the total harmonic distortion (THD) is greater than40dB.OTA’s transconductance gain is0.42μS, the transconductance gain change is lessthan0.01@1Vpp; for six order Butterworth OTA-C BPF the gain reduction is55dBin35.4kHz; in the passband the phase close to linear. Both SC and OTA-C filterachieved the design requirements, the accuracy of the SC filter frequency issignificantly greater than the OTA-C filter, the order and the capacitors are relativelysmall, but the OTA-C does not have a clock circuit design, and has a good phasecharacteristics.