Research And Design Of High Performance Wideband Filter In RF Front-end

Filter plays an important role in the communication system.In the RF receiver,filter is the most used microwave component,as one of the key components of RF receiver,its performance directly determines whether the receiver can work effectively.With the update of communication equipment,the performance of all kinds of functional components in the receiver is required to be improved,and the requirements for filters are more stringent.As a kind of high-performance filter,HTS filter can achieve various high-performance improvements through flexible design,such as greatly reducing insertion loss,making extremely high selectivity,reducing phase distortion of equalization group delay,area miniaturization,out of band high-order harmonic suppression,etc.At the same time,due to the continuous improvement of communication rate,the bandwidth of the filter also needs to be constantly improved.The traditional design method has limited the bandwidth of the filter.In recent years,a kind of multimode filter based on the principle of multimode resonance also shows a higher advantage.This kind of filter not only has a small insertion loss,but also can form a wider passband,which meets the requirements of high-speed communication,it will play an important role in 5G base station communication in the future.In view of the significance of the research on high-performance superconducting filter and broadband filter,this paper chooses the topic and studies,and the main contents of the research include:1.The research and design of wide stopband self equalization HTS filter.Based on the characteristics that the magnetic field distribution and electric field distribution of the open-loop resonator are located in the middle of the resonator and at the end of the resonator respectively,step impedance line and inserted finger capacitor structure are added to the open-loop resonator in this design,and the whole resonator is made into L-shape,which is convenient for cross coupling.Finally,the HTS filter has the characteristics of miniaturization,low insertion loss,wide stopband,flat group delay and so on.The filter has high comprehensive performance.2.C-band wide stopband HTS filter.The filter is always based on the principle of step impedance line.The traditional step impedance line is folded properly to increase the coupling coefficient,The filter can obtain a wide bandwidth.At the same time,parallel coupling feeders are used to further enhance the stop band suppression characteristics of the filter,Finally,the harmonic frequency is suppressed beyond 21 GHz,which improvesthe high-performance filter in the C-band satellite communication system good design ideas are provided.3.The design of high performance double broadband and three broadband filters.The principle of multi-mode resonance is adopted in both filters,Multiple coupling paths are added to the resonator,so that the resonance mode is no longer a single-mode resonance at the frequency corresponding to the half wavelength.In this kind of multi-mode resonator,multiple modes are excited at the same time,and they are distributed from low frequency to high frequency in sequence.In this paper,these modes are used to design multiple filters with wider passband,so that the insertion loss is greatly increased The harmonic frequency is also suppressed to a far position by using the center loaded SIR structure.In the design,the length and width of each branch are preliminarily estimated by MATLAB,and then the simulation software is used to verify and optimize the results.The maximum insertion loss of the two filters in their respective passband is not more than 1d B,and the relative bandwidth can reach more than 10%,which fully meets the application requirements of broadband filters.