High-Selectivity Bandpass Filter with Controllable Transmission Zeros Designed Using an Over-Moded Groove Gap Waveguide Cavity

In this paper, based on the gap waveguide technology, an X-band high-selectivity and low-loss over-moded filter with out-of-band transmission zero point is proposed. The filter has good electrical performance and manufacturing flexibility, which can reduce manufacturing costs. It consists of two cascade cavities designed using a grooved gap waveguide structure. It consists of two cascaded cavities designed using the groove gap waveguide structure. By adjusting the structure and size, it can flexibly control the position of the two transmission zero points in the upper and lower stop bands. The design has very good out-of-band suppression and simple structure. To validate this structure, a filter was designed and optimized, operating in the X-band with a center frequency of 11.1 GHz. It has two out-of-band transmission zeros, with a passband bandwidth of approximately 100 MHz. The maximum in-band return loss is 30 dB, and the minimum insertion loss is 0.4 dB.