Study On Waveform Design And Real-time Processing System For MIMO Radar

Multi-input-multi-output (MIMO) radar has been intensively researched recently.MIMO radar is defined as a radar system with multiple antennas to simultaneouslytransmit diverse waveforms freely, as well as multiple antennas to receive the radarreflected signals. Compared with conventional phased-array radar, the waveformdiversity makes MIMO radar have greater flexibility to achieve the desired transmitbeampattern. Meanwhile the waveform diversity of MIMO radar is an important meansof improving resource utilization of radar system and implementing adaptive allocationof radar resources. Combining with a research project, the work of this dissertation isfocused on narrowband/wideband MIMO radar waveform design, robust adaptivebeamforming and new type radar universal real-time signal processing system.The main contents of the dissertation are summarized as follows.The first part focuses on narrowband MIMO radar waveform design. In order tosynthesize a desired spatial beampattern, which is mapped into a waveform correlationmatrix, a computationally attractive method is proposed. This method decomposes thewaveform matrix into a spatial direction matrix (SDM) and a temporal division matrix(TDM). Then the SDM is formed by using a set of transmit steering vectors, whoseangles can be estimated by MUSIC, and the TDM is constructed by (0,1)-matrix andorthogonal (uncorrelated) waveforms. The proposed algorithm leads toconstant-modulus transmit signals with good auto and cross-correlation property.Furthermore, this algorithm achieves almost the same performance as the cyclicalgorithm while having lower computational complexity than the existing methods. Anumber of numerical examples are presented to demonstrate the effectiveness of theproposed algorithm.The second part focuses on wideband MIMO radar waveform design. For onedimension (1-D) MIMO radar, a fast wideband transmit beampattern synthesisalgorithm based on frequency invariant beamformer (FIB) is proposed, the spectrum ofwideband MIMO radar transmit waveforms are computed by FIB, then alternatingmatrix fitting method is used to design unimodular sequences. For matching the desiredtransmit beampattern of two dimension (2-D) wideband MIMO radar system, theproposed method in1-D wideband MIMO radar is expanded to2-D wideband MIMOradar. In order to eliminate any dependency on frequency of emiting waveform,2-Dfourier relationship between uniform rectangular array (URA) transmit beampattern and spectrum of emiting waveform is used. Then cost function of waveform matchingfrequency response is established, which imposes a constraint on constant modulus.Finally, using alternating matrix fitting method to design unimodular sequences. Theproposed method effectively mitigates frequency dispersion of wideband MIMO radartransmit beampattern. The proposed method requires no matrix inversion and has muchlower computation complexity compared with wideband beampattern formation viaiterative techniques (WBFIT) due to the significant reduction of iteration order. Thenumerical simulations have proved the validity of the proposed algorithm.The third part focuses on robust adaptive beamforming. In order to solve theproblem of performance degradation due to the imprecise knowledge of the arraysteering vector and inaccurate estimation of the sample covariance matrix, A newapproach based on beamspace steering vector estimation for robust adaptivebeamforming is presented. Firstly, by using the complementary set of the spatial sectorin which the actual steering vector lies, beamspace transformation matrix can beconstructed to ensure that the signal of interest is removed from the samplingcovariance matrix. Then a method for beamspace steering vector estimation is derived,and mathematically expressed as the nonconvex Quadratically Constrained QuadraticPrograms (QCQP) problem with one non-convex quadratic equality constraint, whichcan be successfully solved by using SemiDefinite Relaxation (SDR) techniques.Simulation results show the effectiveness of the proposed algorithm．The fourth part is contributed to new type universal radar real-time singal processor.Aming at the structure characteristics of new radar systems (such as MIMO radar,Cognitive radar, etc), the key techniques of radar real-time processing system such assystem architecture and universal design are investigated. An open system architecturefor radar based on switch network is proposed. This system architecture simplifies thecomplex of multiple mudules interconnect, which contribute to improve the efficiencyof task allocation, software design and debugging. Furthermore, this system architectureis suitable for different requirements of radar systems. Based on the proposed openradar system architecture, a new type universal radar real-time signal processor,consisting of fiber processing modules, universal processing modules and high densitystorage module, is designed. This signal processor adopts the concept of modulizeddesign, with high processing proformance, good scalability and high reliability. ForMIMO digital array radar, MIMO receive proceesing method, wideband beamformingand ISAR image are important issues, thus the task allocation scheme and analysis ofreal-time requirement are investigated. The reconfigurable feature of the new universal radar real-time signal processor gives rise to reusability of hardware and scabability.The designed new universal radar real-time signal processor can be comprised ofdifferent modulars for various radar systems, consequently, reusability of hardwaresupporting multiple radar systems, including radar reconnaissance receiver and echosimulator for radar, etc.