Advantageous Exploitation of Characteristic Modes Analysis for the Design of 3-D Null-Scanning Antennas

A novel design strategy for realizing 3-D null-scanning antennas by resorting to the characteristic modes theory is described. By exploiting the variation of the excitation degree of the current modes ( $J-n)$ over the investigated platform, a null of the pattern can be placed in any desired direction in the upper hemisphere. A rectangular conductive plane has been taken into account as test case to validate the design strategy. Design guidelines are provided for selecting and placing the proper exciters in order to realize the suitable excitation of the current. Measurements on a realized prototype are in a good agreement with simulations, confirming the reliability of the proposed approach.