Study On Countermeasures Against Multichannel Imaging Radars

Multichannel synthetic aperture radar possess all the advantages of synthetic aperture radar, utilizing the multichannel feature, it can obtain information like elevation and line-of-sight velocity, through dual-channel cancellation, multichannel synthetic aperture radar can reduce the influence of interference signals, and is of great value in both military and civilian fields. Thus, the jamming techniques against multichannel synthetic aperture radar have quite a bright development prospect.Two typical applications of multichannel synthetic aperture radar are InSAR and SAR-GMTI, at the present stage, the jamming techniques against InSAR are fastened on the influences of RF jamming and rebound jamming on registering, interferometric process and elevation reconstruction, the research on the deception jamming of InSAR is insufficient. Through phase compensation and cancellation, dual-channel cancellation can obtain SAR images with less influence of the interference, thus, the jamming against dual-channel cancellation is much in demand. SAR-GMTI has an early application in military, and is growing rapidly in civilian fields. Currently, the jamming techniques against SAR-GMTI are mainly active deception jamming of several moving forms and passive jamming like rotating corner reflector, the repeater jamming and the rebound jamming remain further research.This dissertation studies active deception and barrage jamming against InSAR and SAR-GMTI from four key aspects, i.e. the deception jamming against two-channel singlepass InSAR, jamming methods against dual-channel cancellation, repeater jamming on SAR-GMTI and rebound jamming on SAR-GMTI. The research is a suppliment to the countermeasures against multichannel SAR at the present stage, it can provide theoretical basis for the practice, and can bring new thoughts for the ECM of imaging radars. The relevant work is supported by the National Defense Pre-Research program during the "12th Five-Year Plan". The main content of this dissertation is summarized as follows.The first part focuses on the active jamming methods against InSAR. The validity of the conventional non-coherent barrage jamming on InSAR is analyzed, the influences of three partial coherent barrage jamming methods on the SAR image are investigated. Based on the analysis of interferometric phase of the interference signal, the influence of partial coherent barrage jamming on InSAR elevation reconstruction is given, and is verified by simulations. The active deception jamming of InSAR using two jammers is proposed, the interferometric phase image is obtained from deceptive DEM, combined with the estimated interferometric phases of the two jammers and the deceptive complex SAR image of either channel, the InSAR deception jamming is divided into two SAR deception jamming. The steps in generating interference signals are studied, some related factors affecting the estimation of the interferometric phase of the two jammers are analyzed in detail. Theoretical analysis and simulations show that the proposed method is effective in the deception of both SAR 2-D images and InSAR 3-D images.The second part investigates countermeasure against dual-channel cancellation. The principle of dual-channel cancellation is reviewed, the mechanism of the dark stripe after dual-channel cancellation is analyzed. Since the motion of a jammer can affect the shape of the dark stripes, the influence of moving jammer on dual-channel cancellation is analyzed. Since the result is restricted in a limited range, the rotating jammer is proposed, the influences of the rotating arm and the rotary speed on the jamming result are analyzed in detail. To address the problem that the rotating arm and rotary speed are too high to put into practice, the method using multi antenna jammer is presented, the antenna emit interference signal on a time division basis, which has the same effect of a fast moving jammer. Two antenna arrays are also proposed. Based on the analysis of the interferometric phase of two interference signals in fast time domain, we develop the approach using two jammers which can also lower the power requirement of each jammer, the phase requirement when the cancellation is invalid is studied.The third part focuses on the repeater jamming on SAR-GMTI. The traditional fixed delay repeater jamming is first proposed to aim at the jamming of SAR and SAR-GMTI. Since fixed delay repeater jamming is of no effect on GMTI process, the sinusoidal delay repeater jamming is developed. The azimuth coverage of the sinusoidal delay repeater jamming is studied, the range coverage method is given, and the jamming-to-signal ratio formula is derived.The fourth part focuses on the rebound jamming on SAR-GMTI. The influences of fixed delay rebound jamming on SAR and SAR-GMTI are analyzed, performances including azimuth coverage, azimuth Doppler mismatch and range offset are studied, radar parameters and jamming parameters affecting the cancellation range are investigated, the relation of the mismatch ratio of the rebound jamming in azimuth direction between target position and the height of the jammer is given. We also developed random delay rebound jamming against SAR-GMTI, The validity of the proposed method is proved by several sets of simulation, and the results show that barrage jamming of SAR-GMTI requires lower JSR than the SAR does.