In this paper, a quad-antenna system for laptop computers is studied. Because two dual-antenna systems can construct a quad-antenna system, the dual-antenna systems in the open literature are utilized. The mutual coupling between the two dual-antenna systems is analyzed and reduced. To validate the design of a quad-antenna system, the quad-antenna system, consisting of two dual-antenna systems proposed in the open literature and a decoupling element, is fabricated and tested. Its measured -10 dB impedance bandwidths are 200 MHz (2.33-2.52 GHz) and 1.62 GHz (4.5-6.12 GHz). The measured mutual couplings are below -15.5/-19 dB at the 2.4- and 5.2/5.8-GHz WLAN bands, respectively. The measured gains are better than 2.4/3.9 dBi with efficiencies higher than 70%/72% at the two bands, respectively. The envelop correlation coefficient is evaluated based on the measured results.
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