Design & Analysis of Large Multimode Antenna Array using Theory of Characteristic Mode

Abstract

Complex antenna design for various applications has always been an interesting but difficult task. Packing hundreds or thousands of antennas in a limited space to form large arrays, without affecting their individual characteristics, increases this challenge many folds. Although there are many 3D EM tools based on full wave methods like FEM, FTDT, MOM etc, available to help the fast turnaround time of antenna design, still they do not provide full insight of design and are largely based on the experience of designer. Out of the few available, Theory of Characteristics Mode (TCM) is one such powerful technique which when applied to any arbitrarily shaped conducting object, provides the characteristic current modes corresponding to that object., These modes are responsible for radiation characteristics of antenna and also provide information regarding its resonance frequency and radiation bandwidth. In this thesis, TCM is used to design a novel 3 port square patch multimode antenna, in which three characteristics current modes radiates at same resonance frequency of 2.4GHz and 100MHz radiation bandwidth. These current modes radiates orthogonally and independent to each other, generating two orthogonally polarized broadside patterns and one monopole like radiation pattern. The antenna was then fabricated and tested for its electrical performance. Proposed 3 port multimode antenna was then arranged symmetrically in a nine faced stacked polyhedron structure to form a compact 108 element antenna array, and analyzed for various performance parameters.