Effect of DGS Utilization on Characteristics of Square shaped CSRR-Based SIW BPF

This paper discusses the effect of defected ground structure (DGS) utilization on the characteristics of substrate integrated waveguide (SIW) bandpass filter (BPF) made of square shaped complimentary split ring resonator (CSRR). There are 2 pieces of DGS pattern with a round and square pattern made on the groundplane. Meanwhile the CSRR has 2 pairs of patterns consisting of an inner ring and an outer ring. The proposed SIW BPF was designed on a 1.6mm thick FR4 epoxy dielectric substrate with the size of 45mm × 40mm. The filter is designed to have the center frequency of 6.75 GHz with the frequency range from 3 GHz to 15 GHz. The investigated parameters of filter include DGS shape, CSRR dimension, distance between vias, and via diameter. It is found that the utilization of DGS and CSRR could enhance the filter characteristics. The characterization results show that the filter with square DGS patterns has the best performance among others with S
₁₁
value of -18.44 dB, S
₂₁
value of -3.01 dB, and fractional bandwidth of 122%.