A cross‐coupled dielectric waveguide filter based on blind holes and via holes is proposed in this study. Using a unique all‐hole design, a fourth‐order cross‐coupled dielectric waveguide bandpass filter is realized by drilling via holes or blind holes in a square dielectric waveguide, followed by coating the surface with thin metal. Magnetic coupling is realized using two blind holes located symmetrically above and below each other. Further, electrical coupling is realized using a combination of two blind holes located symmetrically above and below each other and an interconnecting via hole. Both types of coupling are analyzed and designed. Moreover, a circular via hole is provided in the middle of the square cavity to suppress the parasitic response of the filter. Coupling debugging holes, resonant debugging holes, and feed holes are realized using shallow blind holes, thereby alleviating the process of manufacturing and debugging. The structure of the designed filter is discussed, simulated, manufactured, and measured. The results show that the proposed filter has a center frequency of 3.5 GHz, an insertion loss of less than 0.5 dB, a return loss of less than 15 dB, and a relative bandwidth of 5%, exhibiting excellent performance that includes two out‐of‐band transmission zeros.

A novel dielectric waveguide filter based on isosceles right‐angled triangular (RAT) resonators is presented in this letter. By connecting the vertices of four isosceles RAT waveguide cavities, a square fourth‐order cross‐coupled waveguide bandpass filter is formed. The presented filter uses the partition wall and shallow blind hole to realize positive coupling and the deep blind hole to realize negative coupling. Moreover, the filter facilitates debugging and testing by setting the debugging blind hole on one side of the waveguide and setting the feed blind hole on the opposite side. The design, analysis, and simulation of the physical model of the filter are discussed. The fabricated filter has a center frequency of 3.5 GHz, relative bandwidth of 5%, insertion loss of less than 1 dB, in‐band return loss of more than 15 dB, and two out‐of‐band transmission zeros at 3.27 and 3.65 GHz.

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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.

In this article, a novel isosceles right triangle resonators filter is presented based on cross‐coupling technology. The whole filter is a square structure and it consists of four isosceles right triangle resonators. By introducing negative cross‐coupling between two resonators, a fourth‐order cross‐coupling dielectric waveguide filter with two out‐of‐band transmission zeros (TZs) is implemented. By changing the sign of the coupling coefficient, the TZ can be changed around the passband. Positive coupling is achieved through a coupling partition and shallow coupling blind holes, and negative coupling is achieved through symmetrical upper and lower blind holes. The new resonator structure is introduced and the design, simulation, and physical measurement of the filter are discussed. The results show that the center frequency of the filter is 3.5 GHz and the relative bandwidth is 5.7%. The passband return loss is more than 14 dB, the insertion loss is less than 0.1 dB.