Design and analysis of a broadband electrically small antenna using characteristic mode theory

Abstract

In this paper, a new broadband electrically small antenna is proposed for WiFi application. This antenna consists of a microstrip-feed-line and a parasitic metamaterial structure in the ground plane. In the proposed antenna, a parasitic metamaterial structure is used to overcome the problem of impedance matching instead of using external matching networks that occupy large space. Size reduction and good impedance matching at 2.4 GHz are achieved by placing a meander-line in the very near field of the microstrip-feed-line. The characteristic mode theory is used to analysis the proposed antenna. This antenna is designed to operate at 2.4 GHz and, its whole size is 8.5 mm × 8.5 mm × 1.524 mm (0.068 λ0 × 0.068 λ0 × 0.012 λ0), which is one of the smallest electrically small antennas available at this frequency. A prototype of the proposed antenna is fabricated and, the measured results indicate that the −10 dB impedance bandwidth is 220 MHz from 2.28 to 2.5 GHz. This antenna is made on a single-layer substrate and easily fabricated through the standard planar techniques. The proposed antenna has a compact size and high bandwidth.