Research On Technology Of Distributed Spaceborne SAR Jamming And Anti-jamming

Distributed spaceborne SAR system is a new concept of spaceborne radar system, it can implement high resolution and large swath imaging, MTI(Moving Target Indication) and interferometry, it also has higher performance and more flexibility than single spaceborne SAR and multi spaceborne radar simply netted, so this distributed system is one of the most important directions for the future.It is urgent to study how to protect the normal operation of our distributed system and how to prevent our information from being detected by the enemy's distributed system; therefore, this thesis is devoted to study of jamming and anti-jamming techniques for distributed spaceborne SAR system.Chapter one introduces the past and present studies on distributed spaceborne SAR, jamming and anti-jamming techniques of SAR.The second chapter first introduces the two typical models of distributed spaceborne SAR, then builds the signal model, as well as the radar equation and NESZ(Noise Equivalent Sigma Zero), which make preparations for later studies.The third chapter of this thesis first studies suppression jamming techniques. The jamming power requirement is studied, evaluation of jamming effect is also given through analysis of image. One kind of jamming method using parameter swiftly changed technique is described, through the mismatch of center frequency or chirp rate of LFM(Linear Frequency Modulation) signal, this method can protect certain areas with proper power.The fourth chapter studies the deceptive jamming techniques. Deceptive jamming method based on bistatic location is proposed, through the combination of bistatic location and track prediction, jamming can be focused which ensures the deceptive result. Deceptive moving target jamming method is proposed, and it can cure the problem that jamming scene can not jam the MTI function of distributed SAR system. The jamming principle and focusing result of terrain scattered jamming method for distributed spaceborne SAR system are studied. Corresponding to the problem of single jammer's not being able to produce deceptive jamming, this thesis introduces one method of jammer configuration, through the netted jammer, arbitrary area can be protected with expected jamming power.Chapter five studies anti-jamming techniques based on the flexible geometry. Bandwidth division method is used to cure the problem of wide band, so beamforming process is possible. Anti-jamming method based on periodic uniform sampling reconstruction technique is described with subarray on each satellite, during this process, samplings from all the satellites are combined to be reconstructed into uniform ones to get rid of jamming. At the same time, anti-jamming method based on different kinds of formation geometry is studied; the coarray concept of common array is combined together with the flexible geometry of distributed system, through the combination, higher anti-jamming performance is acquired without increasing the cost of the system. Lastly, a space-frequency anti-jamming method is introduced, combined with the formation geometry using coarray concept, spatial resolution is enhanced, as well as the performance of grating lobes.The sixth chapter studies the anti-jamming techniques based on signal desire. First it proposes a method based on chirp rate jittering, through the process of jittering and thresholding, coherent repeat jammings including terrain scattered jamming are greatly suppressed, which displays the potential use for real environment. Lastly, anti-jamming method based on jittering orthogonal codes at different moments is studied, orthogonal codes are searched with the genetic algorithm, and random initial phase is also used in this method, so great anti-jamming performance is gotten, and the performance is testified through the simulation.