Coupling Spring Design and Insertion Loss Minimization of Second Order MicroElectroMechanical Filters

For a microelectromechanical (MEM) filter a new approach for the coupling spring design is presented. A designed MEM bandpass filter consists hereby of two laterally driven resonance structures which are coupled by a mechanical spring. For this structure an electrical equivalent circuit is presented and analyzed analytically. The transfer function and the correlation between the bandwidth and the coupling spring for this filter are derived. A complete design procedure for micromechanical bandpass filters is presented with simulation results. With changing design parameters the filter response has been demonstrated to be maximally flat as in the case of Butterworth-Filters, or to have a response allowing a wider bandwidth than in the former case. Both of these cases are studied theoretically and simulated for the same frequency range. In respect of the insertion loss value, a modified source and load resistance is applied which keeps it under 1 dB.