Multilayer and anisotropic planar compact PBG structures for microstrip applications

Two novel microstrip planar photonic-bandgap (PBG) structures are presented, i.e., a multilayer PBG and an anisotropic PBG. The multilayer PBG, constituted of uniplanar compact (UC) PBGs stacked up below the line, produces huge gaps (> 140 %) through the suppression of parasitic transmission peaks and can achieve a two-fold size reduction with respect to UC-PBGs. The anisotropic PBG is a uniplanar structure exhibiting a propagation direction and an attenuation direction (AD) in a working range of the order of 35%, deep/sharp gaps broader than 65% in the AD, an excellent insensitivity to the line position and an extreme compact size of the order of /spl lambda//2 by /spl lambda//7.