Phase Coding Signal Set Design For MIMO Radar

Multiple-Inpult Multiple-Output(MIMO) radar has mulitple transmit and receive antennas. According to the configuration of antennas, MIMO radar generally can be divided into two categories: MIMO radar with widely separated antennas and MIMO radar with colocated antennas. With widely separated antennas, MIMO radar can illuminate a target from different angles and obtain the spatial diversity gain, which can combat the target flicker effect and improve the detection capability. For MIMO radar with colocated antennas, each antenna transmits diverse waveforms freely, which can provide the flexible waveform diversity. Compared to the conventional phased array radar, MIMO radar with colocated antennas can provide more system freedom, higher resolution and better parameter identification capability. In this dissertation, we focus on the MIMO radar with colocated antennas, and do researches on the design of the phase coding signal set. The main researches include MIMO radar orthogonal phase coding signal set design with Gerchberg-Saxton(GS) algorithm, orthogonal phase coding signal set design for MIMO radar via an algebraic method, golay complementary sequence with space time coding for MIMO radar waveform design and Doppler resilient complete complementary sequence design for MIMO radar. The main researches are summarized as follows: 1. The problem of orthogonal phase coding signal set design for MIMO radar is studied. In the design of orthogonal phase coding signal set for MIMO radar, a hybrid GS algorithm is presented to solve the problem that signal sets obtained by the existed algorithms have high correlation sidelobes. The presented algorithm integrates an improved GS algorithm with the iterative code selection method. First of all, an optimization cost function based on the total correlation sidelobes energy of the signal set is converted into a simpler quadratic optimization problem. A GS algorithm is amended with extended to multidimensional case and improved the constraints of object domain and frequency domain, and then the improved GS algorithm is used to get a solution of the simplified optimization problem. Then, the results from the first step is further optimized by minimizing the correlation sidelobes peaks using the iterative code selection method, and the signal set with low correlation sidelobes is finally generated. Simulation results show that the autocorrelation sidelobe and crosscorrelation of the designed signal set are very low, meanwhile, compared with the existed algorithms, the proposed algorithm can perform better in terms of computation time. 2. For the complex computation and low efficiency problems of the traditional numerical optimization method in the designing orthogonal phase coding signal for MIMO radar, a method based on algebraic theory is proposed. Firstly, using inverse reduction-multiplication method find the polynomials which are used to design the sequence families F; then the sequence families can be generated by solving the linear recurrence equations via some linear shift registers, whose character polynomials are exactly the ones obtained in first step; in the end, the signal code sets are obtained by mapping the sequence families. The simulation results demonstrate that the aperiodic autocorrelation and crosscorrelation performance of the designed code sets are good, and the sequences number of the sets is large enough. Compared with the numerical optimization method, the efficiency of generating the code sets is greatly improved, which benefits the engineering application. 3. A method of Golay complementary sequence with space time coding is proposed for designing waveforms in MIMO radar. The crosscorrelation of the waveforms are degraded by extended space time coding the pulse trains of the Golay complementary sequences, and the autocorrelation sidelobes are reduced by utilizing the complementary characteristic of the Golay complementary sequence. Hence, the waveform sidelobes after matched filter are reduced. Doppler shift can be introduced by the movement of the target, which will degrade the correlation and the pulse compression performance of the designed waveform. In order to solve this problem, the waveform after pulse compression is Doppler compensated via null space vector weighting method. Consequently, the waveform sidelobes after matched filter are reduced significantly, which benefits the target detection ability and further processing. The simulation results demonstrate the effectiveness of the proposed method. 4. In order to overcome the problem of the Doppler sensitivity of the complete complementary sequence(CCS), an optimization design method is proposed. The design is cast as a constrained minimization problem by introducing an auxiliary variable, then the sequential quadratic programming(SQP) algorithm is introduced to solve the problem. In a given Doppler shift interval, the sidelobes of the ambiguity function are very low and do not fluctuate with the Doppler shift, more specifically, they distribute very uniformly. This demonstrates the Doppler resilience of the designed CCS. Different from the existing methods, this design does not restrict the waveform number, the pulse number and the waveform length, which can increase the flexibility of this design.