Efficient and Accurate Pattern Synthesis for Radome-Enclosed Planar Arrays Using Iterative FFT via Two-Dimensional Least-Square Active Element Pattern Expansion

This work generalizes the iterative fast Fourier transform (FFT) via least-square active element pattern expansion method to efficiently synthesize two-dimensional (2D) patterns with accurate sidelobe and mainlobe shape control for planar arrays with radomes. The 2D active element patterns (2D-AEPs) of a planar array-radome structure are utilized to include the mutual coupling and radome effect. The 2D-LSAEPE method is presented to approximate each 2D-AEP as the pattern by exciting a virtual rectangular subarray with identical element patterns, and the weighting coefficients of the virtual subarray are found by minimizing the least-square error of the 2D-AEP approximation. With the help of the 2D-LSAEPE, the pattern of a planar array with a radome can be efficiently calculated by FFT. To apply the FFT via 2D-LSAEPE for planar array pattern computation, a blocked accumulating matrix is introduced which relates the virtual and physical excitation vectors. In addition, an interpolation-based pre-processing technique is implemented to obtain the virtual element pattern data in uniform grid of the (u, v)-space so as to meet the requirement of employing the 2D-FFT. By integrating the FFT with the 2D-LSAEPE and the interpolation technique, an efficient iterative method is developed to implement accurate pattern synthesis for planar arrays with radomes. Three examples of synthesizing different planar array-radome systems are conducted. Synthesis results show that the proposed method achieves much more accurate synthesis result than the traditional FFT-based technique, while taking much less computation time than some other methods. This verifies the effectiveness of the proposed method.