Wideband multi-beam antenna apertures using metamaterial-based superstrates

We present a new technique for designing a multi-beam, low-profile, high-gain antenna aperture. The proposed design method relies on loading a feed antenna array with a metamaterial-based superstrate. An effective medium approach is used to design the superstrate using magneto-dielectric slabs, which are then realized using low-pass type miniaturized element frequency selective surfaces. Using this technique, a low-profile multi-beam antenna with an overall thickness of 2λ0, inclusive of the separation between the feed antenna and superstrate, is designed to operate at 8-10 GHz. To achieve such a wide bandwidth, the superstrate is designed to work in a true-time-delay fashion at 9 GHz with over 20% bandwidth. When paired with a focal plane array composed of multiple feed antennas, the entire arrangement acts as a multiple-beam, high-gain antenna aperture. Measurement results confirm the wide-angle scanning properties of the proposed antenna in the ±45° range.