Research And Application Of Multi-mode Filter Technology

As an important part of wireless communication system, radio frequency filter is particularly vital to achieve the high performance capability of the whole system. The research of multi-mode filter is of great significance in the fields like miniaturization, ultra-wideband and multiband. At present, Multi-mode filter is mainly researched to realize miniaturization, ultra-broadband and multiband filter. According to the mechanism of "multi-mode", the paper divides the multi-mode filter technology into multi-mode filter based on degenerate mode and multi-mode filter based on high-order mode. Firstly, the method of multi-mode filter based on degenerate mode is summarized and provided as basis for multi-mode filter design. Then the characteristics of dual-mode filter using different structure of perturbation are analyzed, and the reason why there is a zero-point produced in filters is explained. And then an improvement for traditional dual-mode filter is designed, the structure has a smaller size by introducing stub line loader. Also, the simulation of a multi-mode filter cascaded two-stage resonators is designed in the paper, and two different kinds of results are given. This dissertation also researches and designs the multi-mode filter based on high-order mode, the design procedure is summarized, and two kinds of ultra-broadband multi-mode filter are designed and manufactured. The main contributions of this paper are listed below:First, the thesis is classified by the distribution of voltage wave function on the resonator, and the characteristics of square ring resonator is analyzed. Filter design including method multi-mode filter based on degenerate mode and multi-mode filter based on high order mode is summarized. This approach designing of the multi-mode filter has a guiding significance.Secondly, the characteristics of multi-mode filter based on degenerate mode are summarized when the different forms of perturbation is located in the different position. The improved dual-mode filter scheme is proposed by introducing stub line. Without changing the dual-mode case characteristics, the filter can not only has a tuning function, but also achieves further miniaturization, miniaturization degree of 30%. In this paper, we test and manufacture two improved processing dual-mode filter.Thirdly, this thesis proposes a multi-mode filter cascaded two-stage resonators. Two high-performance multi-mode filters are simulated.Fourthly, this thesis analyzes the characteristics of multi-mode filter based on high-order mode. Two ultra-wideband multi-mode filters are processed and tested. The filters are high-performance in the passband range of 3.1GHz ~ 10.6GHz.