Broadband Microstrip Antenna With Left-Handed Metamaterials

A novel type of microstrip antenna is proposed for compact wideband wireless applications. The antenna is composed of six unit cells of left-handed metamaterial (LHM) and a dipole element. The dipole is directly connected to three of six LHM unit cells, which are arranged in a 2 times 3 antenna array form. In this aspect, the proposed antenna is regarded as LHM loaded dipole antenna. The antenna is matched with a stepped impedance transformer and rectangular slot in the truncated ground plane. The coupled LH resonances and simultaneous excitation of different sections of unit cells and dipole result into broad bandwidth. The proposed antenna has a maximum gain of -1 dBi at 2.5 GHz. The measured return loss indicates 63% bandwidth for |S11| < -10 dB over the band of 1.3-2.5 GHz. The overall size of LHM loaded antenna is lambda₀/2.87 times lambda₀/11.27 times lambda₀/315.80 at the center frequency. The radiation of the electrically small LHM unit cells is also demonstrated by the simulated radiation pattern, which is an important concept for the antenna miniaturization.