Virtual Expanding And Phase Synchronization Based Radar Signal Processing

Due to its superiorities in target parameter(angle,range etc.)estimation and detection,radar system has been widely used in the fields of military defense(for intelligence reconnaissance,alert and guidance,weapon control etc.)and civilian(for traffic control,weather forecast,resource exploration etc.).However,its performance decays rapidly for transmit resources(bandwidth,power,etc.)constraint scenario.In addition,the development of electronic counter-measures(ECM)also forms great challenge to radar system.Therefore,researching on the effective signal processing of radar system and improving its performance of target estimation and detection has gained significance attention in the research field.This thesis mainly investigates the signal processing of radar system under transmit resources constraint or jamming scenarios,and proposes a series of algorithms for high range resolution in the pulse radar system and good target detection performance in the multiple-input and multiple-output(MIMO)radar system.The main research works and the innovations of this thesis are as follows:1.A compressive sensing(CS)technique and virtual expanding(VE)algorithm based radar system,i.e.,the CSVE radar system is proposed.In order to improve the range resolution of pulse radar system especially under the spectrum frequency constraint scenario.The receiver of the proposed CSVE radar system first expands the received pulses with the proposed VE algorithm,and constructs the virtual signals which imitates the real ones with the same frequency,thus expands the valid bandwidth.Then,by using the CS technique,both the received and the virtual expanding signals are compressive sensed and the target range estimation are obtained,which further reduces the required spectrum bandwidth.Compared with the existing methods(such as the Capon and Matched filtering method),the proposed CSVE radar system not only reduces the amount of processed data,but also provides higher range resolution.Simulation results verify the superiorities of the proposed CSVE radar in terms of high range resolution under the spectrum bandwidth constraint scenario.In addition,to improve the robustness of proposed CSVE radar system under the frequency interference scenario,the frequency band detection techniques(such as the spectrum sensing technique)are adopted in both the transmitter and the receiver radar.The transmitter can detect and avoid the jammed frequency in-band effectively while the receiver can detect and abandon the jammed pulse.Finally,the flexibility of VE algorithm is utilized to choose the non-interference signal for VE signal processing.Then CSVE radar system achieves high range resolution in jamming scenario.2.An information interactive processing mechanism based MIMO radar system,i.e.,the interactive MIMO radar system and also its phase synchronization algorithm are designed.The two antenna arrays in the proposed MIMO radar system can transmit and receive signal alternatively in non-overlapped timeslots.The existing phase synchronization algorithms(such as Master-Slave,Round-Trip,etc.)only compensate the phase mismatch caused by(local oscillator,LO)but ignore the channel phase offset due to physical distance between different transmitters and the target,resulting in great performance degradation.In order to compensate channel phase mismatch,the weight for each antenna of distributed MIMO radar system should be further optimized especially under the transmit power constraint scenario.For this purpose,the proposed algorithm can achieve phase synchronization at the stationary target only in two sequential timeslots.The closed-form formula derivation of target detection probability and the simulation results verify that the proposed algorithm can achieve higher received(signal to noise ratio,SNR)and high resolution of target detection.In addition,an improved version of this phase synchronization algorithm was proposed for the moving target scenario by predicting and compensating the channel phase offset caused by target moving.Simulation results demonstrate the high resolution target detection performance of the improved algorithm.Motivated by the signal processing of the proposed phase synchronization algorithm,we extend it to the distributed antenna system(DAS)and two new synchronization algorithms are proposed.Simulation results show they can achieve ideal DTB at multiple destinations with lower synchronization overhead.3.The theoretical closed-form of target detection probability of MIMO radar system with different radar architectures under the jamming scenario with different number of jamming signals and different jamming strength is derived.This thesis studies the performance degradation under blanket jamming scenario,and derives the corresponding theoretic formula.The simulation results achieve the perfect matching with the derived theoretical formula.Based on the research results,the performance analysis and parameter optimization of MIMO radar system can be achieved easily.4.A waveform superposition based pulse diversity algorithm is proposed.In order to solve the high side-lobes problem of the existing pulse diversity algorithm when they are estimating the range of the real targets,this thesis proposed a new waveform superposition based pulse diversity algorithm.For each pulse,a cryptographic tag signal is superposed to its waveform as the feature and to be extracted at the receiver radar to discriminate the real and false target.By design the power allocation factors of both the detection signal and the tag signal,a tradeoff between the discrimination performance and the range estimation accuracy can be achieved.Simulation results verify the superiorities of proposed pulse diversity algorithm in achieving both the preferable performance of both the discrimination and the range resolution.