Substrate Integrated Waveguide Balanced Bandpass Filter With Common-Mode Reflectionless and Suppression Characteristics

In this paper, we proposed a substrate integrated waveguide balanced bandpass filter (BPF) with common-mode (CM) reflectionless and suppression characteristics. The presented BPF utilizes the triangular patches, meander-line resonators, and eighth-mode substrate integrated waveguide resonators to realize the bandpass filtering performance. Furthermore, CM reflectionless performance is achieved by adopting the two transmission lines and a grounded resistor. For demonstration, the proposed BPF design is verified, fabricated, and measured. The fabricated BPF's center frequency is 5.2 GHz, differential-mode insertion loss is 1.7 dB, 3-dB passband is 4.7-5.7 GHz, the CM reflectionless band is 3.5-7.2 GHz, the minimum CM suppression within the measured frequency range is 33 dB.