High Impedance Surfaces (HIS) are one of the breakthroughs that have emerged in the arena of modern antenna design, after they were initially proposed in 1999. HISs are proper candidates as antenna ground planes because of the nearly PMC behavior that they exhibit within certain frequency ranges. We have, for the first time, proposed a wideband circularly symmetric HISs and also demonstrated that curvilinear antenna elements have better performance above circular HISs than rectangular HISs. This superiority is attributed mainly to the electric fields radiated by curvilinear antenna elements which interact more effectively and efficiently with circularly symmetric HIS ground planes.
Reduction of Radar Cross Section (RCS) using artificial materials/surfaces has been an area of interest within last few years. One such method is placing Artificial Magnetic Conductors (AMCs) with Perfect Electric Conductors (PECs) in checkerboard pattern. The fields reflected from the checkerboard elements are out of phase by 180◦ and create destructive interferences in two directions. As a result of these interferences, scattered waves are redirected along more than two major lobes. Our group built one of the first checkerboard surfaces using two AMCs to achieve broader 10-dB RCS reduction bandwidth. Also, our group came up with the Phase difference criteria to obtain more than 10-dB RCS reduction which we named as Phase Difference Limitation (PDL) of such surfaces. This is a restriction of such conventional checkerboard designs which limits the RCS reduction bandwidth. More recently, our group has proposed a novel technique to modify these conventional checkerboard surfaces in order to eliminate the PDL of these surfaces and to further increase the RCS reduction bandwidth. This technique has been validated with measured data and successfully increased the RCS reduction bandwidth of the surface. Currently, our group is focusing on expanding this technique for reducing radar signature of antennas.
Leaky wave antennas (LWAs) have been amongst the most active areas of research for the past five to seven decades. LWAs are characterized by high gain and narrow beamwidths. This makes them well-suited for lower power RADAR applications. Current research on LWAs involves developing them using a class of metamaterials called metasurfaces. Metasurfaces are impedance modulated surfaces that enables the guided surface waves to radiate in the desired directions with the desired polarization. The concept of optical holography is used in the design of these metasurfaces to achieve the desired wavefield configurations.