Application of Ultra-Compact Single Negative Waveguide Metamaterials for a Low Mutual Coupling Patch Antenna Array Design

A novel ultra-compact single-negative waveguide metamaterial (WG-MTM) based on a complementary anti-parallel-spiral line (CAPAL) is proposed and investigated by circuit model analysis, electromagnetic simulation and extraction of the effective parameters. The cell is ultra-compact with dimensions of λ₀/22.08×λ₀/22.08, which advances a step further toward homogenized concept. Two band-gaps attributing to the negative permeability and negative permittivity appear when the CAPAL-WG-MTM cells response to the time-varying perpendicular E-field and parallel H-field, and thus a high decoupling efficiency is obtained. Mutual coupling reduction of about 8.27 dB is realized by inserting 7×1 CAPSL-WG-MTM cells between two closely placed antenna elements with an edge-to-edge separation of only λ₀/19.23. Moreover, the radiation characteristics are improved for both the patch element and the antenna array. A higher front-to-back ratio is obtained for the patch element and an increase of 0.64 dB for the gain of the antenna array by using the CAPAL-WG-MTM structure.