Study Of Key Techniques Of COnformal Software Antenna Based On Complex Platforms

With the development of computer science and high speed digital processing techniques, conventional radar and antenna systems based on analog hardware have been replaced by advanced systems based on digital software step by step. Conformal software antenna has not only important engineering application value but also academic value. Conformal software antenna system consists of conformal antennas and arrays, signal and environment detection and classification algorithms, digital beamforming algorithms and control modules. Based on conformal antenna arrays, this thesis focus on several key techniques of software antenna. The thesis is composed of the following five parts:(1) Conformal antenna analysis and design. Aimed at the multiscale characteristics of conformal array (i.e. conformal antennas are composed of elaborate structures of the antennas and electric large structures of the complex platforms) and based on the integral equation theory, the finite element method-boundary integral method is studied carefully. This method is then applied to analyze and design conformal antennas.(2) Fast DOA estimation algorithms for conformal arrays on complex platform. Several search-free DOA estimation algorithms that can be used for arbitrary conformal arrays are studied, including manifold separation technique (MST), Fourier domain method (FD) and space interpolation method. Aimed at that the“shadow effects”and the interpolated error of the conformal array, a sub-array divided method is proposed. Using this method with interpolation ESPRIT algorithm, high speed and acceptable estimation performance are achieved. The method is verified by numerical simulations.(3) Fast DOA-polarization estimation for conformal arrays on complex platform. First, the characteristics of polarimetric sensitive array is studied and the mathematic model of the receiving data is derived. Based on the Root-MUSIC algorithm, the 2D DFT transformation is used to replace the polynomial rooting and to accelerate calculation. This method is extended to arbitrary array configurations for 2D DOA and polarization estimation. It can reduce the computational complexity efficiently with acceptable assurance. At last, using the spaced interpolation technique, the angle-polarization estimation method based on ESPRIT algorithm is extended from planar array to curved array. Compared to 2D DFT method, the calculation speed can be further speed up.(4) Robust adaptive beamforming for conformal arrays on complex platform. First, a space interpolation technique based algorithm is proposed. Using the interpolation, the conformal array with directional elements is transformed to uniform array with omni-directional, which can enhance the performance of the adaptive beamformer. Second, a more general method based on manifold separation technique for robust beamformer is proposed. The method is simple, robust and can be used for arbitrary array. Theoretical and numerical simulations show that this method has a robust performance in the cases of small samples and DOA point errors exist.(5) Low sidelobe, low cross polarization synthesis for conformal array. The low sidelobe synthesis for conformal array is studied using the adaptive method. The cross polarization effects of conformal array is analyzed and studied. The adaptive method and the alternating projection method are combined to speed up the convergence. This method can reduce the sidelobe and the cross polarization efficiently at the same time.The researchers presented in the thesis provide a useful approach in conformal software antenna design, as well as a solid foundation for the further development in this subject.