A Wideband Printed Dual-Antenna With Three Neutralization Lines for Mobile Terminals

A wideband printed dual-antenna for mobile terminals is studied. The dual-antenna, consisting of two symmetric antenna elements and three neutralization lines (NLs), is printed on a printed circuit board. The three NLs reduce the mutual coupling within a wide frequency band. The working mechanism of the three NLs is analyzed based on the $S$-parameters, the surface current distributions, and a simplified equivalent model which provides intuitive instructions to optimize the three NLs. A prototype shows that the measured $-$10 dB impedance bandwidth is 1.3 GHz (1.62–2.92 GHz) and the measured mutual coupling is lower than $-$15 dB at the 1.66–2.84 GHz band. It covers the GSM1800, GSM1900, UMTS, LTE2300, LTE2500, and 2.4-GHz WLAN bands. The radiation patterns are measured and the diversity performances are evaluated.

I. Introduction

With the development of wireless communication, the demand for high quality and high data rate is increasing. Multiple-input and multiple-output (MIMO) is considered as a promising technology to achieve this target [1]. The MIMO technology, characterized by using multiple antennas at the transmitter and receiver, exploits the multipath property to improve the communication quality and increase the system capacity [1]. To achieve the best performance of a MIMO system, antennas on the transmitter and the receiver should be uncorrelated (the mutual coupling is low). Nevertheless, it is still an open issue to integrate multiple antennas with low mutual coupling in the mobile terminals.