Enhancing Frequency-Scanning Response of Leaky-Wave Antennas Using High-Impedance Surfaces

The use of high-impedance surfaces (HISs) to increase the frequency-scanning sensitivity of hollow leaky-wave antennas (LWAs) is presented. The LWA consists of a hollow rectangular waveguide with one of its narrow walls replaced by a partially reflective surface, and it is loaded with a metallodielectric HIS to increase its beam-scanning response. Theoretical results based on a simple transverse equivalent network illustrate the physical mechanism responsible for the improvement, and they are verified by experiments on a prototype working in the 11-16 GHz band.

Sub-mm wet etched linear to circular polarization fss based polarization converters

This communication investigates the potential for fabrication of micromachined silicon sub-millimeter wave periodic arrays of freestanding slot frequency selective surfaces (FSS) using wet etch KOH technology. The vehicle for this is an FSS for generating circularly polarized signals from an incident linearly polarized signal at normal incidence to the structure. Principal issues and fabrication processes involved from the initial design of the core FSS structures to be made and tested through to their final testing are addressed. Measured and simulated results for crossed and ring slot element shapes in single and double layer polarization convertor structures are presented for sub-mm wave operation. It is shown that 3 dB axial ratio (AR) bandwidths of 21% can be achieved with the one layer perforated screen design and that the rate of change is lower than the double layer structures. An insertion loss of 1.1 dB can be achieved for the split circular ring double layer periodic array. These results are shown to be compatible with the more specialized fabrication equipment dry reactive ion etching approach previously used for the construction of this type of structure. © 2011 IEEE.