Printed Multimode Antenna for MIMO Systems

Abstract

A compact printed multimode antenna for Multiple-Input Multiple-Output (MIMO) systems is presented. The antenna consists of a slotted metallic ring antenna excited by four L-shaped microstrip feeding lines, which are necessary to generate four orthogonal radiating modes. The proposed antenna exhibits a performance similar to traditional antenna arrays in MIMO systems, and due to its compact size it is very suitable for mobile terminals or sensors. The Theory of Characteristic Modes is first used to identify the different radiating modes of the antenna and then a set of feeding configurations is proposed so as to excite these modes. A compact printed 2-stage network of 180° hybrid couplers is implemented to feed the proposed antenna. Measured S-parameters and radiation patterns confirm the excellent behavior of the proposed antenna.