Method for optimization of plane waves in the near field

Optimized array processing techniques have been effectively used to achieve acceptable plane wave uniformity throughout a volume in the near field that is necessary for in-situ array calibration and testing purposes and for conducting experiments such as scattering measurements on a large target in a controlled environment. A near field array design is validated for the linear array based on the least squares method. A more useful Near Field Optimized Array (NFOA) based on stochastic algorithms is designed to improve the signal intensity drastically at the designated near field plane wave region while maintaining very good quality of the synthesized plane wave. When used as a projector with the optimized weights, the NFOA produces a nearly uniform plane wave over a large volume in its near field and over a large frequency range. When the same shading coefficients are used at the receiver side, the NFOA becomes a plane wave filter for the field radiation originating from within the plane wave volume which is critical in target scattering analysis. Numerical implementation based on Least Squares (LS) technique, Simulated Annealing (SA) and Genetic Algorithm (GA) are used to obtain the optimum shading coefficients for the individual elements in the NFOA, and the results are compared in terms of intensity of the plane wave and its quality factors.