Novel scheme for design of adaptive printed antenna elements

Previously, we presented an adaptive printed antenna element by placing diode-loaded parasitic metallic strips along the radiating edges of a linearly polarized patch antenna to modify the E-plane radiation pattern while slightly affecting the H-plane radiation pattern. We extend that idea to the design of adaptive printed antenna elements that are linearly or circularly polarized. The basic idea is based on the modification of the EM propagation characteristics (surface waves) of the dielectric substrate by using diode-loaded parasitic metallic strips. The radiation patterns can be changed by turning the diodes on or off. It is shown that the configuration of the metallic strips is dependent on the polarization of the antenna. Thus, two designs are presented for linear and circular polarization, respectively. An adaptive linearly polarized antenna is obtained by using four strips near all four edges of the antenna. This allows us to modify the pattern in the E- as well as H-plane. On the other hand, the circularly polarized antenna requires a ring completely surrounding the antenna element.