A New Multimode Antenna for MIMO Systems Using a Mode Frequency Convergence Concept

A new multimode antenna is proposed in this paper. The structure is based on a mode frequency convergence concept. A microstrip square patch antenna is modified in order to force different modes to resonate at the same frequency. Then, with a common/differential excitation, these modes can be fed independently. Thus, three radiation patterns are available simultaneously, thereby producing diversity. With dimensions less than a guided wavelength (≈ 0.88λ_g), the proposed structure is well suited to reduce the size of multiple antennas used in diversity applications such as MIMO systems. The antenna has been designed in the 2.45 GHz band for Wi-Fi applications.