Radio Frequency Stealth Waveform Design And Processing Method For Airborne Cognitive Radar

Cognitive radar feeds back the perceived environmental information to the transmitter,enabling it to adjust its transmiting strategy in time to improve target detection ability,anti-jamming performance and so on,which has become the research hotspot in the field of airborne radar.Radio Frequency(RF)stealth waveform design technology is an effective way to improve airborne radar transmitting capability.This technology mainly obtains RF stealth waveform through optimization model building and algorithm solving,and combines with advanced signal processing methods,which improves the performance of airborne radars such as Low Probability of Interception(LPI),Low Identifiability(LI)and anti-jamming performance.In this regard,the optimization problems of airborne cognitive radar RF stealth waveform design and signal processing methods are focused on the thesis,and researches on waveform design and receiving beamforming are carried out.The main contents include the following:1.Aiming at the problem that the traditional transmitting waveform is easy to be intercepted and the parameters are easy to be identified,the chaotic modulation RF stealth waveform design method is studied.The typical LPI characteristics such as initial value sensitivity and randomness are summarized.The waveform modulated by intra-pulse parameter is studied by using chaotic sequences.The interception performance evaluation standards and interception processing method are analyzed in the thesis.This method can improve the LPI and LI performance.2.For the RF stealth waveform time-frequency multi-domain anti-interference problem,firstly the joint optimization waveform design method for single radar in timefrequency domain is considered.The problem model minimizing the local autocorrelation function and spectrum notch is constructed.And the novel proximal multiplier algorithm based on MM principle is proposed.This method effectively suppresses the narrowband interferences and improve the weak target detection ability.Then,the frequency domain cooperative waveform design method with two nodes in short baseline is proposed.The narrowband detection signal and wideband cover signal are designed respectively.The signal processing method of phase participation and non-coherent joint accumulation is studied.This method improves the LPI performance and active anti-interference ability of waveform.3.Aiming at the problem of anti-sidelobe interference for airborne cognitive radar,a narrowband beamforming optimization model with minimized integrated sidelobe level under array gain constraint is constructed firstly.The Dinkelbach Algorithm-Coordinate Descent(DA-CD)is proposed.This method realizes the flexible control of the sidelobe level and effectively suppresses sidelobe interferences.Then,a wideband digital beamformer with integer time delay filters is proposed and an optimization model minimizing notch level is established.Two optimization algorithms suitable for different scenarios are studied.This method improves the ability of airborne cognitive radar to resist sidelobe interference.The rationality of waveform and beamforming design is analyzed theoretically,and the RF stealth performances such as LPI,LI and anti-jamming are verified by simulation.Finally,the results show that the above methods can effectively improve the RF stealth capability of airborne cognitive radar in complex electromagnetic environment.