Study On Anti-convolutional Noise Jamming Of The Linear Frequency Modulation Pulse-compression Radar

As modern anti-interference technology like the matching filtering andcoherence processing can sharply reduce the interference effect of ordinarynon-coherent interference pattern，LFM radar has a good anti-jamming ability. Inrecent years， convolution noise has emerged with a form similar to radar signal.Therefore, it can get through the detection of radar receiver smoothly and bringspurious interference to radar. Meanwhile, because of the existence of high-powernoise, it has the characteristics of blanket jamming and can effectively suppress LFMradar. Obviously, this kind of interference has become an important threat to LFMradar, and appropriate anti-jamming methods need to be developed urgently.Against these challenges, related anti-interference methods are proposed, asbelow:Firstly, the principle and parameter characteristic of linear frequency modulationsignal and convolution noise jamming signal have been studied in this paper. Wemake the theory analysis and the simulation. Mathematical models of the two kindsof signals are established, also, we make a comparative analysis of amplitude andphase frequency characteristics of the time-frequency domain waveform.Secondly, makes a comparative evaluation on the Anti-interference capacity ofthe pulse compression technology of Radar. Through MATLAB simulation andcomparative analysis of signal-to-interference rate after pulse compression withnarrowband noise and convolution noise interference, we find that the effect whatRadar restrains the narrowband noise is good, and the restrains effectof convolution noise is not very obvious, also need to specifically looking fora suppression measures.Again, based on radar launch system, the pulse diversity of convolution noiseinterference algorithm is proposed. This algorithm uses four adjacent radartransmitted pulse, to form a special set of transmit pulses, and make some modulationfor each pulse. When suffer with convolution noise, coherent accumulation on eachpulse set received can cancel the interference signal. The convolution algorithm doesnot need to know the signal characteristics of noise, and has little calculations. It’sconvenient to apply in practice. Finally, based on radar receiving system, Algorithm of convolution noiseinterference with orthogonal projection is proposed. This algorithm is mainly usingstrong autocorrelation characteristic of LFM signal. Before the echo signal pulsecompression, make the orthogonal projection matrix of the last undisturbed receivedpulses in radar as Reference signal, to multiply by the current period echo signal, itcan inhibit the jamming signal of current period echo signal. We find thatsignal-to-interference rate after inhibiting is increased by at least23.5dB, whichshows that this algorithm has a better suppression ability for convolution noise.