Multiband multi-antenna system for MIMO wlan box

During the last years, the Wi-Fi applications have spread in a considerable way. The 802.11n evolution of this standard has even promised better performances: high data rate and reliability of the connection. Thus, antennas associated with Wi-Fi applications need to be more and more successful and miniaturized. In order to increase the data rates required in modern communication and reduce the deep fading caused by the multi-path propagating environment, the researchers have proposed MIMO (Multiple Input, Multiple output) and diversity systems which mainly consist in increasing the number of antennas in the receiver [1], [2], [3]. But the major difficulty remains the integration of several antennas in a limited space at the receiver side while keeping a good isolation between radiators. Most of the proposed solutions allow only enhancing isolation in the case of the mono-band systems [4], [5]. In this paper, the design of a MIMO and/or diversity bi-band system operated in the WLAN bands (low band [2.4–2.48 GHz] and high band [5.1–5.9 GHZ]) for Wi-Fi box is proposed. Because of the space dedicated to the antennas in the receiver, a miniature dual-band IFA (Inverted-F Antenna)is at first designed and positioned at the corner of a 100×150mm2 PCB (Printed Circuit Board) Then another identical IFA is placed at 10 mm of the first antenna. To keep a good isolation between the IFAs in both bands, the neutralization technique [4], [6] is used and then improved by inserting a capacitor into the neutralization line. This method allows us to always keep an acceptable isolation level in both bands between the two antennas.