Multi-Field Coupling Analysis Of Microwave Devices And Design Of Multi-Band Coaxial Cavity Filter

With the continuous development of modern wireless communication systems,microwave components such as microwave cavity filters,waveguide circulators and multi-band filters are playing an increasingly important role.Microwave filters are usually used in the front end of radio frequency systems to filter out spurious signals and suppress image frequencies.Among them,cavity filters are widely used in microwave radio frequency communication systems because of their high Q value,low loss,and high rectangle factor.However,in the actual working environment,it is affected by different external environment temperatures,such as low-temperature outer space environment and special high-temperature environment.Due to the thermal expansion and contraction effect of the metal cavity,the shape and size of the cavity filter will change,and the working frequency band will shift,which is called the temperature drift phenomenon.After theoretical analysis and experimental verification,we find that the working frequency band of the cavity filter will shift to low frequencies in a high temperature environment;And in a low temperature environment,the working frequency band of the cavity filter will shift to high frequencies.This kind of temperature drift phenomenon is more obvious in narrow-band filters.Therefore,how to design a reasonable temperature compensation device to ensure the stable operation of the cavity filter under different external temperatures has become a hot research topic.Waveguide circulators are mainly used in microwave communications,electronic warfare,military microwave systems and other fields because of their high power capacity and high reliability.The waveguide isolator can be obtained by connecting a matched load to one of the ports of the waveguide circulator.At this time,the microwave signal can only be transmitted in one direction,and the reflected energy will be absorbed by the load end.Based on the basic working principle of the circulator,this paper designs and simulates a three-port waveguide isolator that works in the X-band.Then,by simulating the real working environment of the waveguide isolator,the heat dissipation performance of the waveguide isolator under the conditions of air convection heat transfer and water convection heat transfer is compared.It provides more references for the design and thermal simulation of high-power waveguide isolators.Dual-band filters are becoming more and more important because they can be used in the multi-band integration of communication systems.With the rapid development of electronic technology in space communication,the use of dual-band filters with high Q value,small size and high rectangular coefficient is increasing.This paper presents a design method of coaxial dual-band filter with wide stopband suppression.By setting the half-window coupling structure and using loaded coaxial resonator,the stopband suppression of the dualband coaxial filter can be significantly improved.Take the L-band coaxial dual-band filter as an example to design and test.The parasitic passband frequency of this design is 3.52 times the center frequency of the low-frequency channel filter,which is 30% higher than the stopband suppression under the traditional structure,which verifies the effectiveness of the method.