Characteristics of microstrip antennas with left-handed material substrates

Discrete complex image method is extended to the computation of Green's function in left-handed material substrates. The radiation performances of microstrip antennas with left-handed material substrates are studied with method of moments. It is shown that this kind of antennas will get similar radiation patterns to the ones of conventional microstrip antennas when |ε_r|≤|μ_r|, and can yield radiation patterns characteristic of narrow main lobes with low elevation angles while |ε_r|>|μ_r|. Potential applications for directive antennas with these unusual radiation patterns of this kind of antennas are proposed.