Limitation on the bandwidth of artificial perfect magnetic conductor surfaces

A perfect magnetic conductor surface reflects electromagnetic waves without phase change of the electric field, in contrast to the 180deg phase change from a perfect electric conductor. Existing structures achieve this condition only at a particular frequency. The phase variation away from this frequency is larger for thinner structures, leading to smaller bandwidth over which the desired condition is achieved to given tolerance. There is fundamental upper limit on the bandwidth of structures based on frequency-selective surfaces arising from the causality and passivity of the structure