Oriented Design of an Antenna for MIMO Applications Using Theory of Characteristic Modes

In this letter, the Theory of Characteristic Modes (TCMs) is used to achieve pattern diversity in order to be used in multiple-input-multiple-output (MIMO) applications. It is shown that TCMs can orient the design procedure by providing an insight into the natural behavior of the analyzed radiating part of the structure. A metallic equilateral triangular-shaped plate is analyzed by TCMs, and its first seven characteristic modes are obtained. Among them, there are two sets of degenerative modes. All these modes are orthogonal. To achieve pattern diversity, it is essential to have two or more orthogonal radiation patterns with identical excitation frequency of the relevant ports. Therefore, the aforementioned sets can be used to acquire the pattern diversity. However, from obtained results, the set with the less practical implementation issues is selected to be excited. To perform the above-mentioned modal analysis, a specific method of moments (MoM) code has been developed and applied to identify different radiating modes. Two microstrip transmission lines were used as feeding parts so as to excite the suitable set of modes.