A Quad-Antenna System for 4G/5G/GPS Metal Frame Mobile Phones

This letter presents a wideband/multiband quad-antenna system for 4G/5G/GPS metal-frame mobile phones. The quad-antenna system has two kinds of antenna elements and four antenna elements. The merit of the proposed antenna system is that a quad-antenna system is achieved under the condition of metal frame, and without using any decoupling structure, the desired bands for 4G/5G/GPS are covered. A prototype was fabricated and measured. For the first kind of antenna elements (including two antenna elements), the bands of 698–960, 1710–2690, and 3400–3600 MHz are covered, and the LTE700/GSM850/GSM900/GSM1800/GSM1900/LTE2300/LTE2500/3.5 GHz bands all are covered. For the second kind of antenna elements (including two antenna elements), the bands of 1440–2690 and 3400–3600 MHz are covered, and the GPS, GSM1800/GSM1900/LTE2300/LTE2500/3.5 GHz bands are covered. The measured isolations are bigger than 10 dB. The measured efficiencies are bigger than 40% at all the working bands. The measured envelope correlation coefficients are very suitable for multiple-input--multiple-output (MIMO) communication systems.