Low-Cost Dual-Loop-Antenna System for Dual-WLAN-Band 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 multiantenna 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 multiantenna 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. Details of a design prototype are described and discussed in this paper.