Research On Design Method For Waveguide Plasma Limiter

High power microwave weapon is a new type of directed energy weapons. High power microwave radiated by directed energy radiation device can couple into a variety of electronic equipment through the antenna, power lines, signal lines, aperture, etc., causing some phenomena like interference, flip/disturb, degradation and damage. Then the protection of high power microwave is particularly important. Based on the three factors of electromagnetic compatibility, this paper studies the characteristics of high power microwave, its coupling way and the calculation method of coupling amount of the front door and sensitive equipment and protection methods of antenna ports.Firstly, through using the waveform of Gauss modulation and square wave modulation as the mathematical model of HPM, the time and frequency domain characteristic of single and repetition frequency HPM is presented. Then according to the coupling way of high power microwave, main sensitive equipment is obtained. The damage mechanism of electronic equipment can be turned into the damage mechanism of the most sensitive electronic components in main circuits of electronic equipment, which is the semiconductor device. This paper analyzes the damage mechanism of bipolar device and MOS device, and second breakdown is the main damage mechanism.Based on Fries transmission formula, the model to calculate coupled power from the antenna is proposed, and three factors influencing the coupled power, change of pitch angle, azimuth and frequency of high power microwave are simulated separately. Change of pitch angle or azimuth influence coupled power greatly to directional antenna; when the frequency of transmitting antenna is among of working frequency band of the receiving antenna, namely in-band coupling, coupled power is relatively high.The concept of plasma frequency can be obtained through oscillation of plasma, and electromagnetic wave, the frequency of which is lower than plasma frequency, cannot pass through plasma; plasma can attenuate incident electromagnetic wave,and the amount of attenuation changes with different frequency. The two characteristics make plasma can be used in protection of high power microwave.This paper puts forward the design principle of waveguide plasma limiter based on the relationship, which should be met, between the electric field strength of incident high power microwave and the breakdown electric field of filling gas in t he limiter, the rise time of high power microwave and response time of the limiter. The specific design method and design process is presented. When a single limiter cannot meet the proposed design principle, cascade limiter can be used. From two aspects o f power capacity and response time, PIN limiter and waveguide plasma limiter can be cascaded, which provide better protective performance. Taking the design of an X-band plasma waveguide limiter as an example, the particular design process is given, and the protective performance of the limiter is simulated, verified the correctness and feasibility of proposed design method.