Octaband WWAN/LTE Dual-Antenna System Decoupled by Two Neutralization Lines with Inductors for Smart Phones

A decoupled octaband WWAN/LTE dual-antenna system occupying a size of 80 mm × 15 mm × 6.8 mm for smart phones is proposed. The proposed antenna system consists of two antenna elements with symmetrical geometry, two neutralization lines (NLs) with embedded inductor, and an inverted-T branch. The two NLs mainly reduce the mutual coupling at the desired lower (704-960 MHz) frequency band, while the inverted-T branch mainly reduces the mutual coupling at the desired higher (1710-2690 MHz) frequency band. The fabricated prototype has a -6 dB impedance bandwidth of 0.3 GHz (0.69-0.99 GHz) and 1.2 GHz (1.66-2.86 GHz) which cover the LTE700, GSM850, GSM900, DCS, PCS, UMTS, LTE2300, and LTE2500 bands. Within these bands, the measured mutual couplings are lower than -10 dB. The measured antenna efficiencies are about 42.6%-60% and 58.3%-78.7% at the desired lower and higher frequency bands, respectively. The diversity performance and the SAR performance are also evaluated.