Research On Response Characteristics Of Low Noise Amplifier Under Strong Electromagnetic Pulse

In recent years,with the increasing demand for miniaturization,integration,and high-speed electronic equipment,the electromagnetic compatibility problem between the various functional modules within the equipment has become particularly prominent,leading to higher and higher electromagnetic susceptibility.When strong electromagnetic pulses(EMP)irradiate electronic equipment,they may enter the equipment in the form of "front door coupling" or "rear door coupling",causing sensitive internal devices to be disturbed or damaged,such as low noise amplifiers(LNA),mixers,and so on.At the same time,due to the strong frequency selectivity of the antenna,the strong electromagnetic pulse associated with the antenna frequency spectrum has a greater threat capability.The LNA is affected by the characteristics of the amplifier's own semiconductor transistors,making it particularly sensitive to strong electromagnetic pulses.Therefore,this thesis mainly focuses on the spectral correlation between the LNA and strong electromagnetic pulses.To start,the response characteristics and thermal damage characteristics of different low noise amplifiers under the action of strong electromagnetic pulses are studied,and the simulation rules are verified through experiments,which is of great significance to the research on the protection methods of low noise amplifiers under strong electromagnetic pulses.In the first part,the basic characteristics of semiconductor transistor are analyzed,and the threat level of three kinds of strong electromagnetic pulse to LNA is determined by combining with the spectrum correlation between strong electromagnetic pulse,radar and communication system.It is clear that HPM-NS is the main interference source of p HEMT LNA in radar,and HEMP is the main interference source of BJT LNA in communication system.In the second part,by analyzing the performance index of LNA and the failure mode of semiconductor devices under the action of EMP,it is determined that Gain and Noise Figure are the main criteria for the damage of LNA,and the working principle and damage mechanism of BJT and p HEMT LNA are summarized.It is clear that the emitter junction cylinder of BJT transistor is vulnerable when the base is injected,and the position where the gate of the p HEMT transistor is biased toward the source when the gate is injected is the vulnerable part.In the third part,through the circuit simulation of the LNA,the response characteristics of the amplifier without thermal damage are studied.At the same time,the numerical physical model of the transistor is established,and the temperature rise characteristics when thermal damage occurs.The results show that with the increase of the HPM-NS amplitude,an avalanche breakdown will occur between the gate and the source of the p HEMT LNA,and the Gain will be significantly reduced.It will cause the phenomenon of instantaneous suppression and instantaneous interference in the LNA,and the pulse characteristic parameters have a certain influence on the recovery time of instantaneous interference.This phenomenon may cause the radar to be unable to effectively detect the target;When the HEMP attacks,the BJT LNA has also suffered recoverable damage,including transient suppression and transient interference,which may cause communication interruption.Then the thermal damage characteristics of Ga As p HEMT were simulated to further verify the damage mechanism of p HEMT under the action of HPM-NS.At the same time,the thermal damage characteristics of BJT under step pulse are studied according to GJB538-88 simulation,and the research has verified that the cylindrical surface of the BJT emitter junction is the main vulnerable part;The simulation results show that the thermal damage threshold of the transistor is related to the pulse characteristic parameters.The thermal damage threshold of both p HEMT and BJT decreases as the pulse width increases,and the slope becomes slower.In the fourth part,a test method of the damage effect of the LNA under different strong electromagnetic pulses is proposed,and pulse injection test is carried out on the LNA based on GJB538-88 to further explores the influence of the characteristic parameters of the pulse on the permanent damage threshold of the LNA.At the same time,the accuracy of the simulation law was verified,and then the LNA protection method for the three types of strong electromagnetic pulses and measures to reduce the response time of the protection module were proposed.