Research On S-band High Performance Cavity Filter Technology

Since the advent of wireless systems,filters have become an indispensable core device.Especially in modern advanced wireless systems(such as radar,wireless communications,electronic countermeasures and satellite communications),the performance of filters determines the overall indicators of the system to a certain extent.For wireless communication systems,with the explosive growth of functions and requirements,the available spectrum resources become more and more scarce,which requires high isolation between adjacent bands,so the requirements for filter performance indicators become higher and higher.A design method of S-band high performance cavity bandpass filter is studied in this paper.The filter designed by this method has low loss and high rejection.At the same time,because of the use of “one-cavity multi-mode” technology and “inner conductor loading” technology,the size of the device is greatly reduced to meet the requirements of miniaturization.The specific research contents of this paper include the following three parts:1?The network synthesis technology of high performance filters is studied.On the basis of researching the network functions of common filters and their frequency response characteristics,according to the characteristics of various network functions,quasielliptic functions,which can meet the requirements of high performance indicators,are selected.The selected network functions are deduced mathematically to obtain their general expressions and the original topological structure of filters,and then according to the requirements of design indicators.The corresponding coupling matrix is obtained from the original topological structure,and the coupling coefficients between all levels of resonators are defined.2?Research on filter resonator and cross-coupling structure.HFSS full-wave simulation software is used to simulate the resonator and coupling structure using “onecavity multi-mode” technology and “inner conductor loading” technology.The working mode and physical structure of the resonator are determined,and the relationship between tuning parameters and frequency response characteristics is analyzed.Then the rough size of the coupling structure is obtained according to the obtained coupling coefficient.The filter model is simulated as a whole,and the parameters of the model are optimized and adjusted to determine the mechanical structure of the filter.3?The debugging technology of the filter is studied.Because the network functions used are sensitive,fault-tolerant and inevitably have processing errors,it is necessary to study the debugging methods.According to the relationship between the tuning parameters and the frequency response characteristics obtained in the simulation process,the actual debugging is guided,and the problems are analyzed and summarized,and the debugging methods for such filters are summarized.Finally,a high performance cavity bandpass filter with 2.146-2.169 GHz passband frequency,less than 1 dB insertion loss,2 MHz transition band and 40 dB suppression is realized.