RF Stealth,Multi-view Imaging And Ultra-high Speed Platform GMTI System Technology For Airborne Ground Surveillance Radar

Ground surveillance aircraft is an important part of intelligence,surveillance and reconnaissance(ISR)system that can carry out long-distance,large-scale and highresolution reconnaissance and surveillance of ground and sea targets under all-weather conditions,and obtain enemy radar positions,artillery positions,missile launching positions,command posts,communication hubs,bridges,ports,airports and other stationary targets,as well as mobile targets such as maritime ship formation,ground vehicles and personnel formation.The airborne ground surveillance radar,whose main functions are synthetic aperture radar(SAR)imaging and ground moving target indication(GMTI),is the core load of ground surveillance aircraft.With the improvement of the performance of land-based air defense detection radar and land-based air defense weapons,the ground surveillance aircraft which performs tasks in the high-risk rejection area are developing towards stealth and ultrahigh speed.Therefore,new requirements are put forward for airborne ground surveillance radar,such as radio frequency(RF)stealth for aircraft stealth,optimization of large aperture antenna layout and system architecture for ultra-high speed and it is required that radar should realize automatic target detection based on SAR image when performing tasks in high-risk rejection area,while automatic target detection based on SAR image requires efficient acquisition of large-scale and multi-view SAR.Aiming at the requirements of stealth and ultra-high speed ground surveillance aircraft for radar,low-interception radio frequency stealth,high-efficiency acquisition of large-scale and multi-view SAR images and the system technology of ultra-high speed platform GMTI,such as multi-input and multioutput(MIMO)distributed array optimization and low-cost and high-resolution space time adaptive processing(STAP)system architecture,are studied in this dissertation from a systemic perspective.The main content of this dissertation can be summarized as the following four parts:1.The design method of low intercept RF stealth for SAR system is proposed from a systemic perspective.Based on the radar range equation of SAR system and the interception range equation of radar radiation signal by electronic countermeasure equipment,the maximum low interception range equation of SAR system is derived.By analyzing the equation of the maximum low intercept range,the design method of the low intercept RF stealth SAR system is proposed.On the basis of analyzing the work process of signal sorting of electronic countermeasure equipment,the working waveform of low interception RF stealth SAR system is put forward.According to the requirement of low interception radio frequency stealth waveform,a new noise SAR imaging system with random variable pulse repetition frequency(PRF)and pulse width is proposed.The corresponding imaging algorithm is given,and its anti-jamming capability is simulated and analyzed.2.In view of the limitations of traditional multi view SAR image acquisition methods,such as small illumination scene,difficult image registration and high implementation cost,a new large-scale and multi-view SAR imaging system and method in one flight are proposed.Compared with conventional multi-view image acquisition methods such as spotlight SAR or multiple flights,the system adopts multi beam,which can obtain large-scene and multiview images in one flight,effectively improving the efficiency of multi-view image acquisition.An improved range migration algorithm(RMA)based on unified coordinate system is proposed.After imaging with this algorithm,the multi-view images can be registered after a fixed time shift,which reduces the registration difficulty compared with the multi-view images obtained by different flight.3.In order to meet the requirement of large aperture antenna for ground slow moving target detection on ultra-high speed platform,a MIMO array architecture based on distributed subarray combined with positive and negative slope chirp signal and its optimization method are proposed to improve the minimum detectable speed of ground moving target for ultrahigh speed platform radar.In the aspect of optimization algorithm,in view of the limitations of the standard genetic algorithm,such as easy to fall into local optimum and slow convergence speed,the standard genetic algorithm is improved,that is,the global adaptive scale transformation operator is used to transform the fitness value,which effectively improves the convergence speed and global optimization ability of the algorithm.The improved genetic algorithm is applied to the optimization of MIMO distributed subarray array.The traditional genetic algorithm for sparse array optimization uses the array element position as the optimization variable.For distributed subarray optimization,the subarray interval is used as the optimization variable to reduce the complexity and computational complexity of the algorithm,and further improve the convergence speed.4.GMTI radar based on ultrahigh-speed platform puts forward the demand for azimuth large aperture antenna.The light and thin antenna array is conducive to the ultrahigh-speed platform to fit large aperture antenna.The low instantaneous bandwidth antenna is easier to realize the thinning of the array than the high instantaneous bandwidth.However,the accurate tracking and target recognition of the ground moving target require the support of the high range resolution image.In order to solve this problem,a high-resolution STAP system architecture based on the low instantaneous bandwidth digital array of transceiver reciprocity is proposed.The system architecture uses different multi-channel arrays to transmit linear frequency modulation signals with different carrier frequencies,and the array transceiver reciprocity can realize the coincidence of the equivalent phase center.In the process of bandwidth synthesis,the phase difference of the target deviated from the beam center does not need to be compensated,and the precise synthesis of large bandwidth signals can be realized,which effectively solves the contradiction between the large aperture array with low instantaneous bandwidth and the high range resolution with large bandwidth.