Linearly Polarized Arrays with Almost Isotropic Radiation Patterns

摘要

A linearly polarized antenna cannot radiate power uniformly in all directions. However, by controlling the aperture excitation, as is done in an array, it is possible to reduce the maximum gain and approach conditions for isotropic radiation. A numerical method is presented which generates a family of designs which depend on a parameter alpha. As alpha approaches zero, the radiation pattern tends to become more isotropic. However, the efficiency is reduced and the sensitivity of the pattern to errors in the aperture function is increased. In some cases this sensitivity is so high as to make the result worthless. The design, therefore, must be a compromise between closeness to conditions of isotropic radiation on one hand, and losses and sensitivity to errors on the other. The sensitivity to errors, expressed by the pattern deterioration for a given level of error, has been evaluated by a numerical experiment (Monte Carlo method). A general relation has also been established between the sensitivity and the losses in the antenna. It agrees with the numerical experiment and can be used as a guide to choose the regularization parameter alpha. (Author)