Low-loss MEMS band-pass filters with improved out-of-band rejection by exploiting inductive parasitics

This paper reports on a new implementation of integrated lumped filters with improved out-of-band rejection and passband loss. Inductive parasitics are exploited to provide additional transmission zeros at the high frequency end, which can improve both the out-of-band rejection and roll-off. Thick silver is electroplated to reduce the insertion loss and achieve high quality factor. An insertion loss of better than 3dB has been achieved for filters across 220MHz to 640MHz with unloaded Q as high as 50. The out-of-band rejection of filters is as high as 60dB. These are believed to be the highest performing integrated filters in terms of out-of-band attenuation and spurious-free response implemented on silicon substrate.