Study On Imaging-Radar Target Feature Manipulation Based On Intermittent Modulation

As an all-day and all-weather micro-wave probing measure,the imaging radar is capable of generating high resolution images of the time-sensitive ground targets,and plays an important part in the reconnaissance and strike integrated system,which detects target and guides weapon to complete the attack task.The imaging radar poses a great challenge for battlefield survival ability of time-sensitive targets.The requirement for countering imaging radar systems have become a basic subject and urgent task in radar jamming area.Based on the intermittent modulation technique,this dissertation aims at manipulating the time-sensitive target,breaks through the limitations of traditional imaging-radar target feature manipulation,deeply studies imaging-radar characteristics of intermittent modulation signal,and then carries on the application of intermittent-modulation in manipulating imaging-radar target feature.The main contents are as follows:First of all,the intermittent-modulation manipulation of imaging-radar target feature by phase switched screen(PSS)is studied.The modulated signal model and the echo signal model illuminated by linear frequency modulated(LFM)radar are analyzed in detail.The output one-dimensional and two-dimensional image characteristics after imaging processing are studied.An improved novel micro-motion passive jamming method is proposed to overcome the drawback of the conventional method,i.e.,the expansion of the jamming stripe along range direction is limited.A novel high resolution range profile deception method and two-dimensional deception method for imaging radar are proposed,which deal with the problem for the dependence on electromagxnetic scattering database,the real-time response difficulty,and the exposure of jamming itself.The jamming effect can be controlled by setting the operating parameters reasonably.Secondly,the intermittent-modulation manipulation of imaging-radar target feature by active frequency selective surface(AFSS)absorber is analysed.The absorption characteristics are studied in detail.The electromagnetic simulation software is utilized to simulate the characteristics of AFSS absorber with different polarizations and incident angles.Then,an experimental sample is made according to the simulation results,and its absorbing characteristics are measured in anechoic chamber.The experimental results show that the reflectance attenuation can be up to 20 dB by setting the control current parameters reasonably in the microwave anechoic chamber.The concept of intermittent scattering is proposed for the first time.The feasibility of intermittent scattering is demonstrated by the experimental samples.It is verified that the AFSS absorber can intermittently modulated the echo signals in the intermittent state.Based on the intermittent sampling and repeater jamming theory,a passive intermittent modulation jamming method for imaging radar based on AFSS absorber is proposed.The proposed method has no retransmitting delay,electromagnetic scattering database,not easy to expose the jamming signal and so on.Finally,the intermittent-modulation manipulation of imaging-radar target feature by active cancellation is studied.A three-stage active cancellation method for countering wideband imaging radar is proposed.By intercepting target echoes and add frequency modulation,this method provides a solution to the mismatch brought by retransmitting delay.An active stealth method against imaging radar is addressed to achieve both target 'hidden' and decoys generation,which combines the ISRJ technique and the active cancellation technique.An improved direct digital false-target image synthesizer is proposed.It does not need to use special hardware circuit,which greatly simplifies the jamming signal generation in real time.The method is simple and it not sensitive to reconnaissance error.