A Wideband Compact WLAN/WiMAX MIMO Antenna Based on Dipole With V-shaped Ground Branch

A wideband printed dipole with V-shaped ground branches is proposed, which is designed for multiple-input multiple-output (MIMO) antennas. It is based on a dipole with an integrated balun, and V-shaped ground branches are introduced to improve the impedance matching. The bandwidth of this element reaches 62.3% (2.30-4.40 GHz), which covers all three WiMAX bands (2.30, 2.50, and 3.30 GHz) and the 2.40 GHz WLAN band. Based on this element, a quad-element MIMO antenna is designed and fabricated. By reusing the V-shaped ground structure between adjacent elements, the size of this quad-element antenna is only 0.31 λ × 0.31λ × 0.01λ. Meanwhile, a bandwidth of 60.6% (2.30-4.30 GHz) is achieved, in which the S₁₁ <; - 10 dB, S₁₂ <; - 10 dB, and S₁₃ <; - 13 dB. Directional radiation patterns with 2.1 dBi average gain are attained, which are very stable throughout this band. This antenna system can be suitable for multielement MIMO devices such as wireless routers and adapters.