Study On Jamming To Chirp Radar And Digital Jamming Synthesis

Various techniques of electronic counter-countermeasures (ECCM) are widelyemployed in ADvanced rADAr systems. Particularly, with the utilizing of the coherentcharacteristic of intra-pulse or inter-pulses, pulse compression and coherent integrationon receiving obviously decrease the efficiency of electronic jamming which signalwaveforms are mismatched to the victim rADAr’s transmitted waveform. Therefore, itis a challenge to the research on techniques of electronic countermeasures (ECM).Thispaper studies the problem of jamming against the rADAr based on linear frequencymodulation (LFM) signals and of the digital jamming synthesis (DJS). The main resultsof the dissertation are as follow:⑴To protect against that the feature of carrier frequency offset is used to identifythe jamming signal general methods are given to hide the feature of the trADitionalshift-frequency jamming. One method is to vary the characteristics of the jammingsignal when the jammer works, such as varying the time length and the amount ofshift-frequency. This paper mainly analyzes some interference style of shift-frequencyusing step wave modulation and saw tooth wave modulation. The second method is tosubtract the feature of shift-frequency jamming. The feature can be hidden by truncatingpulse width with a proper magnitude. As compared with the first method, the secondone has a pulse width mismatch between the jamming signal and the echo. But the lossof the mismatch is acceptable.(2)The jamming effect of trADitional shift-frequency in condition of chirp ratevarying is studied and a novel method of shift-frequency jamming is proposed on thebasis of spectral spreADing-compressing (SSC) method. This method works without theknowledge of chirp rate beforehand and therefore has a quick response. It is effective tointerference to chirp rADAr.(3)On the basis of existing production of SSC method, a higher SSC method is putforward. Analysis and simulation results indicate that the loss of energy after the matchfilter generally decrease with the increase of SSC order.(4)A new algorithm is proposed for rADAr echo canceling based on the SSCmethod. As well known, when a signal with same carrier amplitude, same frequencyand reversed phase simultaneously arrive at rADAr receiving antenna with the echo, theecho may be cacelled. It provides a new method for RF stealth. (5)This paper also presents a new method of wideband waveform synthesis basedon multi-channel DACs. It generates signals striding more than one nyquist regionswithout harsh band pass filter.