An anisotropic substrate grounded with a tensor impedance sheet for control of guided-waves and application to planar leaky-wave antenna design

A simple and practical design technique is proposed to control guided-waves on a dielectric substrate. In particular, by introducing longitudinal slots with a transverse and sub-wavelength periodicity in the bottom metallic surface of a dielectric slab, radial surface-wave (SW) fields can be controlled for bound plane-wave propagation. An analysis of this guide is provided were the longitudinal slots for the modified ground plane are modeled by a tensor impedance sheet. Numerical calculations are in agreement with the full-wave simulations were considerations have been made for the structure anisotropy. Routing concepts are further applied to a SW-fed planar leaky-wave antenna (LWA) defined by a transverse array of microstrip lines with periodic width-modulation. Improved realized gain values for the LWA design are observed (more than 2.5 dB) when compared to a conventional ground plane configuration. Our approach for field control can also be applied to new guides and transitions, routing circuits, and other planar structures which operate at microwave and millimeter-wave frequencies.