A Compact Substrate Integrated Waveguide Bandpass Filter with Harmonic Suppression

In this paper, a compact substrate integrated waveguide (SIW) bandpass filter loaded by hairpin defected ground structure (DGS) is proposed. Due to increased effective capacitance caused by the hairpin structure, the proposed DGS owns a larger quality factor which leads to better performance of band-rejection sharpness and deepness. By combing the high-pass characteristic of SIW and band-rejection characteristic of DGS, the proposed filter achieves good performance in both passband and stopband. In order to verify the design, a bandpass filter with center frequency of 17.25GHz is fabricated and measured. The measured results show good agreement with the simulated results. The measured insertion loss is lower than 1.2 dB within passband from 16.2 GHz to 18.7 GHz, the upper stopband rejection is better than 30dB and harmonic suppression is better than 32dB.