薄膜体声波谐振器( FBAR)是一种薄膜体声波谐振微机电系统( MEMS)器件, 其与振荡电路相结合, 可以将大气环境中的湿度、气压等信息转化为高频振荡信号, 作为环境参数的度量。振荡电路是 FBAR检测系统的关键, 针对实际应用中 FBAR品质因数较低, 导致频率检测电路功耗大、相位噪声特性差的特点, 比较了 3种频率检测方案, 包括现有的 Pierce振荡器、环形振荡器, 以及提出的改进交叉耦合振荡器。 3种振荡器分别采用不同的方法来优化其关键技术指标, 通过比对, 为进一步的检测系统设计提供帮助。本文所采用的 FBAR谐振器品质因数为 205.5, 采用 SMIC0.18 μm CMOS工艺设计振荡电路, 所设计的 3种振荡器功耗分别是26.3 mW,0.382 mW,4.32 mW, 在1 MHz频偏时的相位噪声分别是 -111 dBc/Hz,-152 dBc/Hz,-126 dBc/Hz, 交叉耦合振荡器能满足高精确度的环境变量测量、交叉耦合结构要求。

Film Bulk Acoustic Resonator(FBAR) can be applied in oscillating circuits to transform humility and pressure of atmosphere into frequency signal. Three kinds of oscillating circuits are designed for the FBAR whose quality factor is low: Pierce oscillator, ring oscillator, improved cross-coupled oscillator. Different methods are adopted in the three kinds of oscillators to optimize phase noise and power dissipation. The quality factor of the FBAR is 205.5, and SMIC 0.18 μm CMOS is utilized. The power dissipation of three kinds of oscillators is respectively 26.3 mW, 0.382 mW, 4.32 mW, and the phases are respectively -111 dBc/Hz, -152 dBc/Hz, -126 dBc/Hz at a 1 MHz offset. The improved cross-coupled oscillator can meet the requirement of precise detector.