Design of SIW BPF Matching Network with Ultra-Wide Stopband and High Out-of-Band Signal Suppression Characteristics

This paper demonstrates the design of a substrate integrated waveguide (SIW) bandpass filter (BPF) matching network (MN) with ultra-wide stopband and high out-of-band signal suppression characteristics. The proposed SIW BPF MN can be designed with arbitrary termination impedances (ATIs) including unequal real-to-real, real-to-complex, and complexto-complex. To achieve an ultra-wide stopband that extends to high order harmonic frequencies, dumbbell-shape slots (DSSs) are etched on the ground metallic plane at the input and output ports of the circuit, forming a defected ground structure (DGS). The relation between the attenuation level at the stopband and DGS has been investigated. To validate the proposed method, the SIW BPF MN was designed at the center frequency (f0) of 10 GHz. The designed SIW BPF MN were designed with ATI of 15+j 15-to-50 Ω. The proposed SIW BPF MN provides very good frequency selectivity with stopband attenuations better than 45 dB and 29 dB measured from 1 GHz to 8.7 GHz and 10.6 GHz to 30 GHz, respectively.