Research On The Coherence And Countermeasure Of Wideband Drfm

Deceptive jamming to wideband radar is one of the important aspects in wideband radar Electronic Counter Measure (ECM). Digital Radio Frequency Memory (DRFM) with the characteristic of coherent storing and coherent repeating is widely used in deceptive jamming systems. How to improve the fidelity of false targets, and how to counter deceptive jamming to wideband radar are the hot problems in the field of radar countering recently. This paper has studied the two questions form the following aspects.Firstly, combining the imaging model of rotation platform, the signals of ISAR imaging via STRETCH processing is deduced. Then, quantization and architectures of DRFM are presented; later, the general structure and signal form of deceptive jammer to wideband radar based on DRFM have been researched.Secondly, the effect that Local Oscillator and clock jitter and quantization error take to the coherence of jammer signals is developed; phase errors generated by these factors have been considered together with I/Q channels imbalance. The effect of the image signal generated by I/Q channels imbalance has been analyzed. The simulation results indicate that, after LFM pulse compression, I/Q channels imbalance make the major lobe and Signal Noise Ratio reduce, and make the level of side lobe increase evidently.Thirdly, the analysis of the jammer signal and spectrum after phase quantisation, performed by radio frequency digital memory devices, is approached. The effect of time delay quantisation is analytically evaluated, in combination to the phase quantisation. The quantisation process by DRFM changes the spectrum of a jammer signal. Results show that, the spectrum of the signal presents spurious terms induced by phase quantisation, and, the effect can be reduced by using 4 bits DRFM and higher quantisation bits.Finally, aiming at countering deceptive jamming to the wideband radar, the technology of frequency agility about Electronic Counter Counter Measures to SAR is advanced. Then, to solve the imaging problem about wiadeband frequency agile radar, correlation algorithm and compressed sensing algorithm are presented to achieve pulse compression in azimuth. The simulation results indicate that the two proposed algorithms are effective.