Printed, low-cost, dual-polarized dual-loop-antenna system for 2.4/5 GHz WLAN access points

A low-cost, printed three-antenna system suitable to be embedded inside a wireless access point (AP) for multiple-input multiple-output (MIMO) applications in the 2.4 and 5 GHz WLAN bands is presented. The antenna system comprises three circular dual-loop antennas occupying a moderate area and printed on the same layer of a circular antenna substrate. Each dual-loop antenna further includes a large outer loop and a small inner loop, both operating at one-wavelength resonant mode and sharing common antenna feeding and grounding. The antennas are set in a sequential, rotating arrangement on the substrate with an equal inclination angle of 120° to form a symmetrical multi-antenna structure. The antenna substrate is further stacked above the system circuit board of an AP by a small distance. In this case the design can fully integrate the circuit board of the AP as an efficient reflector for loops into an internal multi-antenna solution. The results showed that well port isolation were obtained together with high-gain and dual-polarized radiation characteristics over the 2.4 and 5 GHz bands.