Holographic Surface Leaky-Wave Lenses With Circularly-Polarized Focused Near-Fields—Part I: Concept, Design and Analysis Theory

A novel concept of planar printed-circuit microwave lens, based on the transformation of a cylindrical surface wave into a modulated leaky wave, is presented in this paper. Inspired on holographic concepts, the TM₀ cylindrical leaky wave is properly tapered across the two-dimensional surface by using an Archimedean-spiral shaped slotted printed-circuit, so that it is obtained a quadratic-phase, quasi-uniform amplitude aperture distribution which creates a highly focused circularly-polarized near-field pattern. The first part of this paper describes the general analysis and synthesis methodology to obtain planar holographic lenses with high radiation and focusing efficiency. As an example, a printed-slot lens with 6λ₀ diameter and focal ratio F/D = 1 operating at 10 GHz is designed and theoretically studied by simulations. The second part of the paper concentrates on the prototype and measurements.