Design Of Resonator-iris And Ridge Waveguide Dual-mode Bandpass Filter

With the rapid development of wireless communication technology, it requires higher performance filter, such as excellent frequency selectivity, low insertion loss, volume miniaturization, the larger bandwidth, and the farther spurious bands. This article focuses on both Self-resonant iris filters, with low insertion loss, wide passband, farther spurious response, and dual-mode ridge waveguide filter with compact structure.Design theories of systematic filter were introduced and field modes in the rectangular waveguide were analyzed. We analyzed the discontinuity of the two-port network by pattern matching method, we obtained theoretical values of the coupling coefficient of each mode in coaxially symmetric waveguide-step, and also gave the theoretical value of the coupling coefficient of each mode in rectangular waveguide to the double-ridged waveguide. An equivalent circuit of the inductive irises, the capacitive irises and inductive post were analyzed using the equivalent circuit method, and their equivalent susceptance value was obtained.This article proposed two new self-resonant irises. One is called convex iris, the structure of this iris is very simple and its characteristics were analyzed. The convex self-resonant iris was applied to design a waveguide bandpass filter, which has a center frequency of9.95GHz, with relative bandwidth of26%. The other is the double-ridged iris, it was applied to design a waveguide bandpass filter, which has a center frequency of6.70GHz, with relative bandwidth of20.9%, the filter simulation result showed that its spurious passband appeared in two times of the center frequency.The article described how to extract the coupling matrix of the generalized chebyshev filter, simultaneously, the two most commonly used topology structure, CT and CQ were introduced. We compled matlab program of cross-coupled filter with these theories. A novel dual-mode ridge waveguide structure was proposed, then, a dual-mode cross coupling bandpass filter was designed with the dual-mode resonator. This filter has compact structure, small size, and good band rejection.