Monolithic silicon micromachined Ka-band filters

This paper describes a novel kind of filter at Ka-band on silicon substrate, which is based on the substrate integrated waveguide (SIW) design and MEMS fabrication process. Inductively coupled plasma (ICP) deep etching is used to form the square via-holes of SIW cavities. A 5-pole micromachined filter is made from rectangular cavities integrated into a silicon substrate and is fed by coplanar waveguide(CPW) transmission-lines through current probes. Measured results show a 0.5 dB loss with a 6.5% bandwidth at a center frequency of 30.9 GHz. The final size of the filter chip is 10.0 mm x 2.7 mm x 0.4 mm. This micromachined filter gives compact size and outstanding performance with relatively mature batch process.