A small-size MIMO antenna for portable devices in Bluetooth/WIMAX/WLAN/UWB applications

This paper presents a small-size multiple-input-multiple-output (MIMO) antenna for wireless portable device applications. It entirely covers the Bluetooth (2.4–2.484 GHz), Worldwide Interoperability for Microwave Access (WiMAX) (3.4–3.69 GHz), Wireless Local Area Network (WLAN) (5.15–5.825 GHz) and ultra-wideband (UWB) (3.1–10.6 GHz) operating bands. This antenna consists of two planar polygon printed monopole (PM) antennas, a rectangular slot and a triangular trim on the antenna element to lower down the low-cutoff frequency for improving the impedance matching, and a stepped ground stub to improve the isolation. Two rounded corners are simultaneously used on the ground for the impedance matching at medium-high frequency. Simulated and measured results prove that the −10dB bandwidth of this antenna is from 2.4 to 11 GHz, and the isolation is less than −15dB in the entire band. Its size is only 40×36 mm
²
on a cost-effective FR4 substrate.