Circular planar coupler for UWB 2-D communication

In this paper we propose a new planar proximity coupler for ultra-wideband (UWB) two-dimensional communication (2DC). In 2DC systems, microwaves are transmitted into and received from a waveguide sheet across the surface by using a dedicated coupler. The coupler, differently from ordinary antennas, transmits microwaves not into the air but into the sheet, and receives them not from the air but from the sheet. The coupler is a circular conductive patch, and an inner smaller circular portion of the patch is removed. The structure is complementary to a circular patch antenna for over-the-air UWB communication. The return loss of a fabricated coupler was less than -5 dB in a frequency range of 3.1-10.6 GHz. The transmittance between two identical couplers laid on a 135 × 68-cm² anechoic sheet was also evaluated. The measured results indicate that the major signal transmission path was not in the air but through the sheet, as expected.