Compact artificial magnetic conductor designs using planar square spiral geometries

Compact spiral artificial magnetic conductors (AMC) have been investigated in this paper. First, single and double spirals are examined to achieve an in-phase reflection at a lower frequency compared to a conventional patch element of the same size. However, these two designs generate a large cross polarization. The cross polarization affects the operating frequency and bandwidth. In order to eliminate the cross polarization effect, a four-arm spiral element is introduced. This geometry does not generate a cross polarization, and an operating frequency that is 49.45% lower than the reference patch element has been achieved.