Researches On Microwave Multi-mode Dielectric Resonators And Filters

With the rapid development of wireless communication technology , mobile base stations and RF systems have more stringent requirements on the performance of microwave devices, especially for the miniaturization, low loss and high suppression of microwave filters are becoming increasingly demanding. In this paper, the multi-mode dielectric filters have the characteristics of multi-mode and volume multiplexing, which can realize the miniaturization of the filters , the dielectric filters also have the feature of high Q value, which can realize the low loss . So the research in this paper has important engineering application value.In this paper, we do some research on multi-mode technology and dielectric filters . A three-mode dielectric filter of TE01?and HEH11 mode based on slotting technique is proposed ; a dual-band dielectric filter based on the mode of TE01? and HEH11 is proposed.The specific research contents are as follows:1. Slotting along the radial direction of 45°/135°/225°/315°on the traditional cylindrical dielectric resonators makes the resonance frequencies of TE01? and HEH11 to become same,So that a dielectric resonator with mixed three-mode cavity is constructed;According to the asymmetrical electric field structure of the modes, a microstrip substrate is provided on the surface of the dielectric resonator, and a metal-conduction band coupling structure of the sickle type is used on the substrate to construct a tri-mode dielectric filter,the tuning of the frequency of each mode and the adjustment of the coupling coefficient are realized by using a plurality of metal screws and dielectric screws in the cavity. Three - mode dielectric filter is processed,debugged and tested. The results are good, low loss is achieved, and the volume is reduced2. Based on the traditional cylindrical dielectric resonator, by using single TE01? mode and HEH11 dual mode to realize the two passbands and the three-mode double-pass dielectric cavity filter is realized. In the implementation of the specific filter, the structure consisting of a vertical cylindrical metal conductor and an arc-shaped metal conductor is used as an input / output port coupling structure;The TE01? mode and HEH11 (horizontal polarization) mode coupling between two cavities is realized by a double capacitance probe structure; coupling; using some metal screw adjust the frequency of each mode and realize HEH11 two-mode coupling between two cavities.Through the physical processing, debugging and testing, good results is tested.we achieve a dual-band work and the volume has been reduced.3. In additions, a dual-frequency coupler is studied in this paper. A kind of ladder impedance parallel coupling line is proposed and applied to the design of dual frequency coupler with arbitrary coupling coefficient and large frequency ratio. The 20dB coupler and 6dB coupler with frequency ratios of 1GHz / 7.5GHz and 1GHz / 5.2GHz are designed respectively. In addition,a broadband dual-frequency coupler can be realized by cascading multiple symmetrical ladder impedance parallel coupling lines, and the method of design and examples are given in this paper. The three types of couplers are processed with lower return loss, higher isolation, wider bandwidth and smaller size than the traditional single-frequency coupler.