Substrate Integrated Waveguide Filter with A Slot in The Middle of Defected Ground Structure

Abstract

The main problem when designing a bandpass filter for microwave and millimeter-wave are the compact size, low insertion loss, high return loss and the sharpness of selectivity. Substrate integrated waveguide (SIW) with defected ground structure (DGS) offer the realization of bandpass filter has low insertion loss, compact size, high return loss, easy to fabricate and more effective cost than using waveguide filter. This research proposed SIW and DGS. DGS is not etched on ground plane, but it is etched in the top layer with the purpose of not disrupting the current flow on the ground. The DGS design is a square open-loop with a slot in middle section to meet low insertion loss, compact size and high return loss. The simulation results give the good performance at range 7. 61–9.88 GHz with the insertion loss values less than 0.6 dB and the return loss values higher than 14 dB while the measurement give the insertion loss values around 3 dB and the return loss values higher than 8 dB. The SIW with three cascaded cells of a square open-loop with a slot in the middle section DGS give the realization bandpass filter more compact and better performance than one cell of DGS.