A Four-Antenna System With High Isolation for Mobile Phones

In this letter, a four-antenna system with high isolation for mobile phones is presented. The antenna system, which consists of one main antenna and three auxiliary antennas, is located on the phone circuit board with a size of 135 × 65 × 0.8 mm
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. The main antenna located on the top of the circuit is used to send and receive signals, which adopts improved monopole antenna, to cover LTE700/2300/2500, GSM850/900/1800/1900/UMTS, and 2.4-GHz WLAN bands efficiently. Three auxiliary antennas with the same size of 40 × 6 × 0.8 mm
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are respectively located along the two vertical sides and the bottom of the circuit board. As receiving antennas, these auxiliary antennas work in the 1880-2690-MHz band. By suitable arrangement and design, the isolation between antennas of higher than 15 dB can be obtained, and the efficiency of the antenna system in the working frequency band reaches 40% or above, which can meet the requirements of antenna performance in mobile communication area.