Eigenmode Analysis of an AMC Ground Plane for Wideband High-Gain Antennas

When trying to enlarge the bandwidth of antennas based on artificial magnetic conductors (AMC), the radiation pattern tends to split at broadside. A rectangular non-periodic design has been proposed by Mateos, R.M. (2006) to overcome this problem. An eigenmode analysis based on the method-of-moments (MoM) technique is performed to study the wave modes supported by an AMC consisting of a backgrounded array of square patches. It reveals that the propagation of a bounded mode is avoided by a cut of the AMC surface in the H-plane. Besides this, reducing the patches length in the E-plane direction, causes such trapped mode to appear outside the band of interest; while the surface may support a leaky wave.