Research On High Power Microwave Breakdown Characteristics Of Cavity Filter

The cavity filters are often used in narrowband receivers due to their small insertion loss and high out-of-band rejection.The power capacity characteristics of the cavity filters are important concerns in microwave engineering applications.Most of the literature studies mainly focus on the microwave breakdown characteristics of cavity filters under continuous wave or long pulse conditions,but few research on the transient narrow pulse breakdown effect of cavity filters in narrowband high power microwave environment.The research work of this thesis is helpful to understand and master the mechanism of high power microwave breakdown effect of cavity filters,and provides technical basis for high power microwave protection of narrowband receivers.Taking the S-band comb-line cavity filters for example,the microwave pulse power capacity of the filters is studied by using the microwave device breakdown simulation software SPARK3 D and the three-dimensional particle simulation software CHIPIC.The atmospheric pressure,metal material and device temperature's impacts on power capacity are simulated.The relationship between the breakdown threshold law,microwave pulse width and microwave power parameters is deeply analyzed.The cavity filter model is designed and processed,so as to carry out the high power microwave breakdown effect test.Simulation and experimental studies show that SPARK3 D can give cavity filters long pulse or continuous wave power capacity estimation,but it can't accomplish transient narrow pulse breakdown simulation;however,CHIPIC has the transient microwave breakdown simulation capability,and its simulation result trend is consistent with the experiment data.So that CHIPIC can be used for microwave breakdown effect test under HPM electromagnetic environment.The three-dimensional particle simulation data under different microwave pulse parameters illustrates that with the increase of pulse width at the same power,the state of the cavity filter can be transitioned from no breakdown to critical breakdown,and terminally it may reach the state of complete breakdown.Within the pulse width limits of this research work,the power threshold range of microwave breakdown is in approximately inverse proportion to the microwave pulse width.Meanwhile,the increase of power in the same pulse width can also lead to the similar experimental results.Due to the data from the gas discharge breakdown test of high power microwave,we can see obvious tail erosion phenomenon,and the phenomenon becomes even more visible when increasing the port input power.Moreover,the HPM breakdown threshold range of this S-band comb-line cavity filter can be estimated to be between 400 W and 700 W.