A Pattern Approximation Method for Distorted Reflector Antennas Using Piecewise Linear Fitting of the Exponential Error Term

Integrated structural-electromagnetic (EM) optimization design is of great importance in the area of antenna design. The quick and exact calculation of patterns for distorted reflectors is an important research topic. In this communication, based on the previous works, a novel pattern approximation method using piecewise linear fitting is presented. The exponential error term in the physical optics (PO) formulation is first approximated by a series of straight lines through the piecewise linear fitting by least-square algorithm. Then, the radiation integral on each structural element is expressed as the summation of the ideal term and perturbation term, which are both weighted by the combinations of coefficients of the corresponding straight lines. Finally, the far field is derived as a simple linear function of structural nodal displacements in a matrix form by assembling the radiation integrals on all the structural elements. Simulation results show that the proposed method (PM) could save the storage space because there is no second-order term of the nodal displacements, facilitate rapid calculation by recalling the prestored data, and has high calculation accuracy even for large size of surface-error profiles.