CPW band-stop filter using unloaded and loaded EBG structures

Two different structures of unloaded and loaded electromagnetic bandgaps (EBG) are proposed. The models of the unloaded and loaded unit structures are derived by equivalent circuit approach and full-wave electromagnetic simulation is used for extracting the values of the lumped elements in the circuit. A band-stop filter (BSF) has been designed with flat response at a selected frequency by cascading the unit EBG structures. The EBG filter is fabricated on high resistivity silicon substrate employing a microelectromechanical systems (MEMS) surface micromachining process. The measurement results for the loaded EBG reveals a 20 dB stop-band with a bandwidth of 13.2 GHz. The lower and the higher pass-band insertion losses are less than 2 dB and 4.5 dB, respectively. EBG band-stop filters fabricated by the MEMS process have immense potential to be integrated with CMOS devices owing to compactness and low cost.