Characteristic Modes for Orthogonal Beamsteering Using ESPAR

A method based on the Theory of Characteristic Modes (TCM) for finding orthogonal beamsteering radiation patterns of electronically steerable parasitic array radiator (ESPAR) is proposed. This method can be used to design single-radio-frequency (RF) multiple-input multiple-output (MIMO) systems for Internet-of-Things (IoT) applications in next-generation wireless communication. It can directly generate a set of symmetrical and orthogonal pattern basis for beamsteering purpose and demodulated reference signal transmission. In addition, the input impedances of ESPAR are the same for all pattern basis so that impedance matching can be achieved by a fixed matching network. Simulation example of a 5-element circular dipole ESPAR is provided to demonstrate the effectiveness of the proposed method.