THEORETICAL-STUDY OF GRATING LOBES REDUCTION USING METALLIC PHOTONIC BANDGAP MATERIALS (MPBG)

A linear array of three half-wavelength dipoles above a metallic refle ctor is analyzed. The results are then compared with those of the same array above a different kind of metallic photonic bandgap materials. The aim is to find a structure which allows the greatest reduction of the grating lobes (GL). This reduction can be obtained either by a des tructive interference in the direction of the grating lobes or by usin g propagation inside the MPBG, propagation of normal incidence only (m ain lobe), or in the GL directions only. Then, an MPBG is selected and is completely analyzed (plane wave response, the radiation pattern wi th just one dipole and with the array in different configurations). As one solution is based on the propagation of particular modes inside t he MPBG, this solution can be enhanced by the use of an MPBG reflector on the other side. But this solution is not perfect since there are g rating lobes in the E-plane due to the way the waves are guided in the MPBG. One last structure is presented in order to suppress this grati ng.