Compact and low profile co-located MIMO antenna structure with polarisation diversity and high port isolation

A compact co-located MIMO structure with high port isolation is proposed for 2.4 GHz WLAN application. The antenna structure consists of a proximity-coupled square ring patch antenna, and a probe fed planar inverted F antenna co-located inside. The operating frequency of the two radiators is designed to be at the same frequency, and a high port isolation below 25 dB is achieved with an extremely narrow edge to edge inter-antenna space of 1 mm (0.008). The total lateral size of the co-located radiators is only 0.28 0.28 , i.e. only about 25 of the size of a half-wavelength dual-port patch antenna. The MIMO structure gives high gains (4.0 dB), low correlation (0.2), and high diversity gain (about 10 dB).