Research On Wide Stop Band And Adjustable Technology Of Microwave Filter

Microwave wireless communication technology has become one of the most dynamic technologies in the world.Especially in recent decades,the widespread use of satellite communications,navigation and remote sensing,mobile communications,and electronic countermeasures has driven the rapid development of wireless communications technology.Multi-band,multi-standard communication makes the electromagnetic environment more and more complicated,which puts forward higher performance requirements for microwave filters.For example,wide stopband technology has obvious advantages in reducing out-ofband interference and improving signal purity;tunable filters can improve system integration in military countermeasures and device reuse,reducing cost and volume.In this article,we will analyze and study the wide stopband and adjustable technology of microwave filters.In the study of wide stopband characteristics,this paper proposes wide stopband technologies suitable for rectangular waveguide filters,dielectric resonator filters,and stripline filters.1.By studying the formation principle of the parasitic passband and the analysis of higher-order mode coupling,this paper proposes a new rectangular waveguide filter design scheme.This solution can reduce the coupling of higher-order modes without affecting the transmission of the fundamental mode,so that the higher-order modes cannot form a parasitic passband,thereby improving the stopband performance.2.This paper proposes a design method for dielectric resonator filters,which can significantly improve the stopband performance and frequency response symmetry.A metal plate is added to the dielectric resonator filter to suppress the transmission of higher-order modes to improve the stopband performance.By introducing the hybrid coupling structure,the dispersion effect of the coupling structure is compensated,the influence of the dispersion effect on the frequency response symmetry is reduced,and the performance of the dielectric resonator filter is further improved.3.A design method of a wide-stopband low-pass filter is given.By introducing a stepped impedance resonator,a number of transmission zeros are added outside the passband,and the wide stopband characteristics of the low-pass filter can be achieved by optimizing the number and position of the zeros.At the same time,the introduction of a stepped impedance resonator enables a miniaturized design of the filter.The above three design solutions applicable to different scenarios are efficient,convenient,low cost,and superior in performance,which constitute a relatively complete wide stopband technology research.Simulation and actual test results verify the effectiveness of the method.In addition,the tunable technology of the filter is studied in this paper.Based on the analysis and research on the tunable scheme and tunable mode,this paper proposes a stable tuning condition suitable for mechanical tuning of waveguide filters from the perspective of the coupling matrix.The characteristics of the change of the resonator's self-resonant frequency and the change of the coupling coefficient when the filter is stably tuned are proposed.An electromagnetic simulation model of the tunable filter was established and stable tuning was achieved in the range of 500 MHz.The electromagnetic simulation results verified the validity of the method.