The Self-breakdown Effect Of Filter And HPM Protection Application

The front-end configuration of a typical microwave receiver consists of a receiving antenna,a filter,a limiter,a low noise amplifier and a mixer.Among them,the low noise amplifier and the mixer are sensitive devices,sensitive to external strong electromagnetic waves,and vulnerable to high power microwave front door attacks.The traditional protection technologies mainly include filtering and amplitude limiting,which are arranged in a serial topology and are functionally independent of each other.It is difficult to achieve the electromagnetic environment protection function of HPM compatibility in time domain and frequency domain in a device.Therefore,this thesis proposes to use the resonant structure in the waveguide band-pass filter to realize the mechanism of strongfield transient self-breakdown effect under the HPM electromagnetic environment,so as to realize a pre-stage HPM protection scheme with time domain and frequency domain in the microwave front end.The scheme is as follows : expanding the filter stopband width,using the characteristics of wide stopband transmission suppression to complete the frequency domain protection of microwave front-end;When the HPM pulse is input,the specially designed filter resonant structure quickly completes the transient microwave breakdown and realizes the energy reflection of most microwave pulses,so as to realize the HPM amplitude limiting protection function of the microwave front-end in time domain and energy domain.Obviously,the broadband stop-band characteristics of waveguide band-pass filter need to be studied firstly in this thesis.Secondly,it is necessary to study the short microwave pulse transmission response in waveguide filter under HPM electromagnetic environment,and obtain the law of microwave breakdown effect under narrow pulse,which provides a scientific basis for the design of this special plasma limiter.Based on the capacitive loading technique,a wide stopband waveguide bandpass filter with special resonant structure is studied.The power capacity of the waveguide filter is calculated by using the corona analysis module of SPARK3 D,and the resonant structure of the waveguide filter is adjusted to balance the normal working power capacity requirement of the waveguide filter and the appropriate HPM breakdown threshold.In this thesis,the PIC particle simulation software CHIPIC,which is widely used in the domestic HPM industry,is used for the numerical simulation of transient microwave pulse breakdown.Starting from the macro-particle model,based on PIC simulation and Monte Carlo collision method(MCC),the transient microwave pulse breakdown model of waveguide filter in HPM electromagnetic environment is constructed.Taking the design of X-band waveguide HPM protection device with center frequency of 9.05 GHz and bandwidth of 400 MHz as an example,the simulation calculation shows that the 40 d B suppression bandwidth covers 10GHz-20.93 GHz,which realizes the wideband out-of-band HPM protection.The initial limiting threshold of the waveguide filter based on the tip cone loaded resonant structure is 1.1k W.When the HPM power reaches 20 k W,the peak leakage energy is less than 13 u J,and the limiting isolation degree of the waveguide filter is greater than 20 d B.The response time is largely independent of the microwave pulse width,and the peak leakage energy is largely independent of the pulse width,and decreases with the increase of the input power.The calculation results verify the research idea of HPM protection compatible with time domain and frequency domain proposed in this thesis.Combined with solid-state PIN limiting technology of microwave front-end back-stage circuit,HPM protection performance can be further optimized and improved,such as higher limiting isolation.The experimental study on the narrow-pulse breakdown characteristics of waveguide bandpass filters under different microwave pulse parameters is also carried out in this thesis.The thesis also carried out small signal testing and HPM injection experiments under low pressure conditions to verify the simulation results.