A wire-grid lens antenna of wide application part I: The wire-grid lens--Concept and experimental confirmation

A novel broad-band lens antenna consisting of a pair of circularly symmetric wire grids with varying grid spacing is described. The antenna is useful for beam scanning at lower frequencies such as at HF where dielectric and waveguide-type lenses are impractical. It should also prove useful in HF communications applications. A single lens structure with multiple feeds could serve as a high gain, high resolution antenna on many different circuits simultaneously. In addition, it could become useful as a printed-circuit lens antenna at microwave frequencies. The property of a pair of grids that makes it suited for lens structures is that the velocity of a wave propagating between two grids can be varied by varying the ratio between the grid spacing and the mesh size. The measured performance of an experimental model of the HF wire-grid lens antenna has demonstrated the feasibility of the basic idea underlying the antenna. The model was tested in a 2:1 bandwidth and a sidelobe level of lower than -20 db was measured. In principle, the bandwidth of the lens can be made as large as desired.