Directional coupler for transverse-electric surface waves
Publication Date: 2009-May-29
The IP.com Prior Art Database
The invention is a directional surface-wave coupler (SWC) that launches transverse-electric (TE) mode electromagnetic surface waves (SW) into a surface-wave medium (SWM). An electromagnetic surface wave is any wave confined to propagate along the two-dimensional interface between two medium, e.g. the interface between dielectric and air is the simplest case. An ideal surface wave’s fields propagate along the surface with sinusoidal variation and decay exponentially away form the surface. The fields have the form eikx e-αz , (See fig. 1) where k is the propagation wavenumber in the propagation direction in the SWM, and α is the decay constant away form the SWM surface exponentially away form the surface SWs can be used to communicate with and/or power devices distributed on the SWM surface. A TE SW is a surface wave whose electric field is parallel to the SWM surface and perpendicular to the direction of propagation. An SWM is any medium that supports SW propagation. It can be composed of the interface between two dielectric materials, such as kapton and air, or it can be created out of complex engineered textures applied to a surface (an example is shown in Fig. 2). The SWC is a device designed to transmit and receive SWs to and from the SWM without coupling to background radiation propagating in free space. An ideal SWC, when transmitting, will couple all of its energy to the SW in the SWM without radiating any power away form the SWM. Likewise, an ideal SWC, when receiving, will receive power only form SWs in the SWM and will not couple to any external free-space radiation.