DGS Loaded Substrate Integrated Waveguide Dual Mode Cavity Filter

novel substrate-integrated waveguide (SIW) dual-mode cavity bandpass filter with a loaded defected ground structure (DGS) is proposed. The SIW dual-mode cavity operates in two modes, TE110 and TE120, and the field distribution of the TE110 mode is altered by installing a metal perturbation aperture in the middle of the cavity to bring its resonance frequency close to that of the TE120 mode, forming a bandpass filter with two resonance points in the passband. A DGS structure is embedded at the ground level of the SIW to introduce a transmission zero in the high-frequency rejection band, thus improving the rejection performance of the filter for the high-frequency rejection band. The simulated and measured results show that the center frequency of the filter is 3.75 GHz; the 3 dB bandwidth is 0.3 GHz; the relative bandwidth is 8%; the return loss is less than -15 dB; and the insertion loss in the passband obtained from the simulation is about -0.35 dB, while that obtained from the measurement is 0.4 dB lower than that of the simulation, and the filter has a transmission zero near the high-frequency stopband of 6 GHz, which enables the high-frequency parasitic passband to move away from the passband of the filter. Except for the passband, all other signals in the Sub6 GHz band can be effectively suppressed by the filter. This design combines the SIW dual-mode cavity with the DGS structure to design the filter, which can realize the flexible adjustment of bandwidth and transmission zero point, and the design method is simple and innovative. The filter can be applied to the 5G n77 frequency band, which has a certain application value.