Planar Near-Field Plates

This paper presents planar near-field plates that can tailor the electromagnetic near field and produce desired subwavelength focal patterns. These plates consist of concentric annular slots on a circular grounded dielectric slab excited through a coaxial connector. The annular slots are loaded with lumped element impedances which are designed to produce a prescribed subwavelength focal pattern. The procedure to design such plates is outlined. The designed plates are studied through full-wave simulation and the generation of desired subwavelength patterns is demonstrated. Several near-field plates are also fabricated and measured. It is shown that the experimental near-field patterns are in close agreement with simulation. Furthermore, experiments confirming the planar near-field plates ability to tailor the electromagnetic near field are presented. Planar near field plates may find application in near-field imaging and probing systems, biomedical targeting devices, and high density data storage.