Potential advantages of hexagonal-shaped over square-shaped unit-cells metallizations regarding the angular stability of Artificial Magnetic Conductors

The potential advantages of using hexagonal-shaped unit-cell metallizations instead of square-shaped ones to enhance the angular stability of Artificial Magnetic Conductors are studied based on simple patch and loop geometries. For a specific resonance frequency and a given dielectric substrate, it is shown that the angular stability is enhanced when increasing the gap distance g from the metallization to the edge of the unit-cell from a certain value, while maintaining suitable operating bandwidth. This effect is observed for both patch-based and loop-based unit-cells and is even more noticeable for hexagonal-shaped metallization. A simplified equivalent circuit model for the unit-cells under study is used to give an insight on the observed behavior. A prototype of the hexagonal-shaped loop-based unit-cell for g=0.9mm has been fabricated in order to experimentally characterize its angular stability in an anechoic chamber, since it is the most stable of the ones under study.