Electromagnetic theory of wire-grid lens HF antenna

In this paper, the electromagnetic theory of the electrical properties of the wire-grid lens HF antenna leading to a calculation of the radiation patterns is presented. The wire-grid lens HF antenna is an extremely broadband antenna based upon the wave-focusing principle of the Luneburg lens. In the calculations, the fields interior and exterior to the circularly symmetric lens antenna are expanded into modes which are orthogonal in the circumferential dimension. A differential equation describing the radial behavior of each mode is derived from the equivalent circuit parameters of the wire grids. The numerical solution of this differential equation and the calculation of the radiation patterns is discussed. The calculated radiation patterns are compared to measured radiation patterns for representative frequencies in the HF frequency band (3 to 30 Mc).