Fast near-field far-field transformation for phaseless and irregular antenna measurement data

[摘要] The characterization of antenna radiation patterns by transformed near-fieldmeasurements requires accurate amplitude and phase data. This represents aproblem since expensive measurement equipment is required, especially atmillimeter and submillimeter wavelengths (Isernia et al.,1996). Amplitude-only antenna field measurements aretheoretically sufficient for the unique determination of antenna far-fields.Therefore, phaseless techniques are of special interest. However, therequired field transformations are extremely challenging, since they arenonlinear and strongly ill-posed.

In this work, the amplitude-only or phaseless near-field far-fieldtransformation problem is formulated as a nonlinear optimization problem. Thelinear radiation operator within the nonlinear formulation is evaluated usingthe fast irregular antenna field transformation algorithm (FIAFTA). A hybridsolution procedure is described which combines a genetic algorithm with aniterative conjugate gradient (CG) search method. Numerical results prove theefficiency and flexibility of the formulation and it is shown that thealgorithm remains stable when the noise level in the measurements ismoderate. Nevertheless, regularization techniques might be beneficial tofurther improve the robustness of the algorithm.

[学科分类] 电子、光学、磁材料