Study Of Algorithms On Suppression Of Radar Active False Targets

By means of precise replication and reproduction of the radar signal through thedigital radio frequency memory (DRFM), the modern deception electronic countermeasures (ECM) has entered a era of coherent false targets. From the point view ofradar, such false targets can easily obtain radar coherent processing gain, such that theyare capable of affecting or even screen the detection and extraction of true targetsstealthily. Moreover, the preset parameters extracted by subsequent processes have theabilities to further consume the resources of radar and protect true targets, and as aresult an error decision may be made about the current target or air intelligence.Actually, it is a powerful technology measures to counter various types of radars,especially advanced radar systems.In this dissertation, the issues of the electronic counter-countermeasures (ECCM)of radars under the conditions of active deception ECMs have been addressed. On thebasis of observing the frontiers and the development trends of the ECCM field, thisdissertation focuses on the radar active range, velocity and multiple false targets byexploiting the models of jamming and radar and the features of false target styles. Theessential researches of this dissertation include the following aspects.First, the definition of the radar active false target ECMs and the specific researchobjects are ascertained, and that the domestic and international research status anddevelopment trends of the corresponding ECCM are also reviewed. Based on these, thesignal generation and the receiving/processing on radar side of the DRFM-basedjammer, as well as the models of range and multiple false targets are analysedsystematically. Subsequently, the principles of radar range tracking and mechanism areanalyzed in details, and the model of velocity ECM of pulsed Doppler (PD) processingmode is derived also. These are the background for further ECCMs given as below.Second, a temporal pulse diversity cancellation algorithm is proposed to countermodern ECMs, which not only has the ability to generate false targets with all thequalities typical of the true targets specified, but also can produce complicated multiplefalse targets by means of intra-pulse modulation. Through transmitting specific pulse signal set in slow-time domain and forming the received signal set by exploiting thereplicating properties of the DRFM of jammers, this approach is capable of cancellingthe protruding spikes of the jammer at the output of matched-filters. It has theadvantages of not requiring parameter estimation of the jammer. In consequence, effortsare made to mitigate the stationary hypothesis involved in slow-time approach. Thisissue is resolved through producing new vectors from the original transmission signalsin joint slow/fast-time domain. The results are that the associated conditions imposedupon are lifted and the method is practicable in rapidly varying conditions since nocancellation is required across different pulse repetition intervals (PRI). Particularly, thismethod is applicable to broad DRFM repeat jammer in electronic warfare (EW) areaand including some novel complicated multiple false target ECMs. Ulteriorly,considering the ECM equipment generally does not store and handle the wholetransmission pulse of the victim radar especially for surveillance radars which use largetime width signals to function in a long range, a suppression algorithm based on thejoint time-frequency pulse diversity is proposed. Due to the fact that the terms used forcancellation are received simultaneously, the repeat ECM signals can be cancelled atcurrent received pulse. The presented algorithm is applicable even if the jammer iscapable of repeating the intercepted radar pulse instantaneously.Third, a pulsed-Doppler velocity false target rejection approach is derived on thebasis of the PD processing mode and the corresponding jamming model. By using thePD sliding window analysis as well as the matched-filtering technology in slow-timedomain, this method endows the PD radar with ideal anti-jamming effect forPulsed-Doppler velocity false target.Fourth, an adaptive algorithm is presented to counter against the range gatepull-off/in (RGPO/RGPI) jammers, which are also referred to as range gate walk-off/inor range gate stealing. By exploiting the error range information, a biased weight isupdated in every range tracking interval in the presence of the jammer to balance theenergy with regard to the target pulse. Accordingly, this enables the split gate system tofocus on the target incessantly.Finally, an adaptive cancellation method for LFM radar to counter against repeatfalse targets which may overlap the true target both in time and frequency domain ispresented. With a special reference signal, the true and false target signal can be fully separated by applying the stretch processing. Consequently, an adaptive notch filteringis utilized to estimate the jammer, and a cancellation approach is performed to cancelthe false target component provided that there is slight time-delay difference betweentrue and false targets. Additionally, an anti-jamming scheme to counter the RGPO/RGPIECM is provided based on this method, and that it is also analyzed by using a radarmeasured data. As expected, the results validate the proposed scheme.