Low-profile WLAN MIMO PIFA Antenna System for Laptops with Large Screen

This paper proposes a low-profile two-element wireless local-area network (WLAN) multi-input multi-output (MIMO) antenna system designed for laptops. The primary and secondary elements are mirror-imaged 3-D metal-plate-loaded planar inverted-F antennas (PIFAs), each measuring only 31 mm x 2 mm x 2 mm. Although structurally simple, each PIFA can generate low- and high-frequency resonant modes through its long- and short-branches, respectively. In addition, the meander shorting metal section can easily be adjusted to shift the resonant frequency and to improve the impedance matching. Without any additional matching circuit or chip components, the antenna can cover the 2.4/5.2/5.8 GHz WLAN bands with a profile height of only 2 mm, which is smaller than the record low in the literature. Moreover, with the two PIFA elements deployed on the left and right sides of the top edge of the display ground plate, the measured isolation is larger than 23 dB in the low-frequency (high-frequency) band, and the measured realized radiation efficiency is at least 52% within all operating bands.