Research On Jamming Techniques Against SAR-GMTI

This doctoral dissertation addresses the jamming techniques against SAR-GMTI,such as passive jamming techniques including chaff jamming and rotating angularreflectors to affect stationary and moving target imaging,1-D and2-D false targetsjamming technique, noise frequency modulation, sinusoidal frequency modulation andsawtooth frequency modulation based on false targets jamming. The main topics of thisdissertation are listed as follows:1. One-dimensional and two-dimensional imaging characteristics for the twotypical imaging radar systems, moving targets detection and parameter estimationtechniques are discussed. It forms the theoretical basis of the study on jammingtechniques against SAR-GMTI. For chirp-subpulses stepped frequency radarone-dimensional ranging images of stationary targets, motion targets with uniformmotion, uniformly accelerated motion are analyzed. Using the stationary phase principle,their characteristics in high resolution imaging are analyzed. Using the moving distancebetween the peak in ranging image and the peak in high resolution image movingtargets velocity can be estimated. For dual channels SAR-GMTI DPCA is adopted todetect moving targets in the imaging scene. Combined with ATI technique movingtargets radial velocity is estimated by its imaging phase. By experimental data it isconfirmed that fast moving targets which speed is below blind speed can be detectedeasily, and the parameters are estimated more accurately. Slowly moving targets aredifficult to detect. Though they can be detected their parameters estimation error isbigger.2. For the passive jamming has many characteristics which are radar type, positionand motion state can’t be known in advance and are realized easily, based on thescattering characteristics of chaffs and rotating angular reflectors their echoes aresimulated and their imaging characteristics are discussed in one-dimension andtwo-dimension. Made an emphasis on discussing rotating angular reflectors many peaksappear in the1-D high resolution images. In the2-D images micro-doppler effectappears along azimuth to form interference trips. By simulated they can cover themotive targets in the protected area to jam the detection of SAR-GMTI.3. Based on echoes characteristics for chirp-subpulses stepped frequency radar a1-D false moving target jamming method is proposed by using false targets template ofuniform moving targets and uniformly accelerated moving targets and transmitting signals convoluted. The frequency of radar transmitted signals is shifted many times byusing the linear relation between the Doppler frequency and the time. Then phase inevery pulse is compensated. Lastly it is convoluted with false moving target templates.Many false targets peaks can be got. By detection many moving targets with the samevelocity are found. If the distance between the radar and the jammer must be consideredthe phase change caused by the distance must be compensated. Errors in radarparameters estimation have less influence on the1-D compressed image. But they canmake peaks in the high-resolution image moved and make pulses wider. There arebigger errors in the parameters estimation.4. Aimed at2-D scene imaging the approach based on man-made map is proposedwhich is convoluted by transmitting signals to protect some areas on the ground. Makean analysis of jamming image defocusing and the imaging area changing if theestimated radar imaging parameters in the man-made map are inaccurate. But it has agood cover jamming effect. The generation method of2-D false targets was analyzed.The2-D false targets templates corresponding with different antenna positions areconvoluted with received radar signals. It forms deception jamming and more accurateparameter estimation can be got. Based on the relation of frequency and time in2-D thefrequency of received radar signals is shifted and convoluted with false target templatesto get the many-false-target jamming covering a certain area. Analysis of the simulationresult shows that the jamming can not create false targets to deceive but has a goodcover jamming effect.5. For the purpose of the fault which took a long time to create many false targetsusing shift-frequency several frequency modulation jamming methods are proposedbased on false targets jammings that are noise weighted frequency modulation jamming,sinusoidal weighted frequency modulation jamming and sawtooth weighted frequencymodulation jamming. Made an analysis of frequency characteristics shifted-frequencyof false targets seems to create many false moving targets in the ranging and thecross-ranging. Jamming effect is discussed and targets parameters estimation can be got.It is similar that many false targets jamming is becoming a cover jamming when thetargets distances are closer or targets mutually overlapping. Simulation and conclusionsare given to verify that these methods have a better jamming effect.