微机械滤波器3 dB通带特性参数新计算模型

New analytical model for 3 dB bandwidth of MEM filter

以含2个振子的微机械滤波器为对象,提出了一组3dB截止频率、3dB带宽和通带波纹度计算模型.首先,考虑到微机械滤波器的阻尼很小,在振动方程的基础上推导出了通带波纹度近似计算模型.然后,将微机械滤波器的幅频响应函数在2个固有频率处做Taylor二阶展开,再考虑到幅频响应函数的一阶导数在2个固有频率处近似为零,推导出了3dB截止频率及3dB带宽近似计算模型.最后,用计算实例证明了这些近似计算模型的精确性.

A set of new analytical models for 3 dB cutoff frequency, 3 dB bandwidth and ripple of a series two-resonator microelectromechanical system （MEM） filter is presented. Seeing that the damping of the MEM filter is very small, a new analytical model for the ripple of the MEM filter is derived firstly. Then the magnitude response function of the MEM filter is expended in two-order Taylor series around two natural frequencies respectively. The new analytical models for 3 dB cutoff frequency, 3 dB bandwidth are derived based on the fact that the first derivative of the magnitude response function is near zero at the two natural frequencies. The set of new models is validated by comparing its results with the results from conventional method.