Circular cross-coupling dielectric waveguide filter based on 90-degree sectoral resonators

In this study, a circular cross-coupled dielectric waveguide (DW) filter was realized based on 90-degree sectoral resonators. The filter is formed by splicing four 90-degree sectoral DW resonators (SDWRs). A shallow blind hole (BH) was set at the center of each 90-degree SDWR to adjust the resonant frequency. The magnetic coupling between the resonators was realized through the rectangular wall and shallow BH. Electrical coupling between the resonators was achieved through deep BHs. The overall structure was designed, simulated, and fabricated. The measured results demonstrate that the designed filter has a center frequency of 3.6 GHz, bandwidth of 200 MHz, insertion loss less than 1 dB, in-band return loss greater than 15 dB, and two out-of-band transmission zeros at 3.38 and 3.82 GHz.