Study On The Limiter Of Beidou Navigation Receiver Under Strong Electromagnetic Field

In electronic warfare systems,high-power microwave weapons can directly and effectively attack the receiver through the antenna.So we must take measures to protect the receiver from damage of high-power microwave weapons.Because of high sensitivity and narrow bandwidth,Beidou navigation receiver badly needs protective measures.As an important power protection device,the limiter plays an important role in protecting the front end of the receiver.So developing a limiter suitable for Beidou navigation receiver is of great significance to improve the anti-attack ability of the receiver.This thesis developed a limiter suitable for Beidou navigation receiver with high performance through the method of theoretical analysis,simulation and experimental verification.Firstly,we determine the design indicators and formulate a scheme of the limiter.The limiter is divided into the main limiter circuit and the auxiliary circuit.By discussing the influence of different parameters of PIN diode on limiter performance in power limiter,we select PIN diodes with a model of CLA4603-085LF and CLA4606-085LF.When designing the main limiting circuit,we study the influence of cascade limiter on the performance of the limiter,and finally determined the circuit structure of the two stage cascade limiter.We model the limiter and make simulation analysis and measurement.The simulation and measured results were ideal.Then,aiming at improving the performance of the circuit,we design the auxiliary circuit based on the cascaded limiter.The auxiliary circuit composed of the coupler and the detector is used to apply the DC bias to the limiter,which realized closed-loop control.We propose a parallel microstrip line coupler suitable for the Beidou B1 frequency band.By simulating and measuring it,we find the results meet the design requirements.We propose an AC-DC voltage multipliers with high detection efficiency,then add impedance matching network at the input end of detector,while adding a low-pass filter at the output end.We have carried out the simulation and test verification,and the results are slightly inadequate.Finally,we combine the various modules of the limiter into a single unit and make a co-simulation of layout and schematic of limiter.The simulation results show that the limiter has good performance in the B1 band of Beidou.After that,we carry out S-parameter experiment,continuous wave power injection experiment and square wave pulse injection experiment.The measured results show that the S parameters of the limiter are slightly insufficient,and the limiter has good performance in CW wave injection.The square wave signal with a peak value of 10V and a pulse width of 200ns is suppressed well through the limiter.The limiter overcomes the shortcoming of the high threshold level of the passive limiter,and solves the problem that the semi-active limiter needs an additional power supply.In the design of the circuit structure,on the one hand,we introduce the voltage multiplier detection circuit into the design of the limiter to improve the detection efficiency;on the other hand,we combine the direct-transmission line of the directional coupler and the transmission line between the cascade-type limiter rationally to simplify the circuit structure and increase the power capacity of limiter.