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 3 dB has been achieved for filters across 220 MHz to 640 MHz with unloaded Q as high as 50. The out-of-band rejection of filters is as high as 60 dB. 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.