Design of the Multiband Substrate Integrated Waveguide Filter using Coupling Matrix based on Frequency Transformation

This paper presents the design of substrate integrated waveguide (SIW) based multi-band filter using the frequency transformation approach. The steps involved in the extraction of coupling matrix elements and the equivalent circuit model for the generalized multi-band filter design are briefly explained. To validate the synthesis method presented in this paper a second-order dual-band bandpass filter is designed with the Chebyshev response. The two passbands are designated at 10.1 – 10.2 GHz and 10.4 – 10.5 GHz with fractional bandwidth (FBW) of 0.985% and 0.957% respectively. The maximum return loss for each passband is 20 dB. Very good agreements are achieved between theoretical responses and full-wave simulations.