An electromagnetic blocking structure includes a dielectric substrate with at least one conductor layer in the dielectric substrate, the at least one conductor layer has a plurality of first unit cells of a first type without four-fold symmetry, and a plurality of second unit cells of the first type, the plurality of first unit cells and the plurality of second unit cells are arranged in a grid pattern with each first unit cell among the plurality of first unit cells being oriented substantially 90° relative to each second unit cell among the plurality of second unit cells.