MIMO antennas with U-shaped ground and three protrued strips for WLAN applications

This paper proposes a monopole type MIMO antenna at WLAN band for dongle application. The MIMO antenna consists of two identical monopole antennas on both ends of an FR4 substrate and operates a frequency band at 2.45 GHz. The antenna is fabricated on an FR4 substrate of permittivity of 4.4, thickness of 1.6 mm, and loss tangent of 0.0245. The isolation mechanism is by cutting U-slot and introducing three isolation elements, which are extended from the ground plane; one is located on the center part of the antenna portion and two strips are located symmetrically at the edges of the U-shaped ground. The overall dimensions (25 × 50 mm²) of the proposed MIMO antenna including an antenna portion (14 × 25 mm²) and a system ground (25 × 36 mm²). The prototype is constructed and investigated. Form the design results, the measured S21 within WLAN 2.4GHz band is below -15 dB; the radiation patterns are with an omni-directional characteristic. In addition, the antenna with the simple structure and good performances is suitable for applying in WLAN system of small size.