MIMO Antenna Using Resonance of Ground Planes for 4G Mobile Application

Abstract

A MIMO antenna using the resonance of ground planes is proposed for 4G mobile application. A resonant mode is generated when the double ground planes (upper and lower) in the mobile terminal are excited as the radiator. By combining the resonant modes contributed from both the antenna element and the ground planes, the proposed MIMO antenna realizes a wideband property over LTE band 13. In addition, an inductive coil is employed to reduce the antenna volume. These approaches not only simplify antenna design but also effectively improve bandwidth and efficiency. The proposed MIMO antenna has an excellent ECC value of below 0.1 because of the nearly orthogonal radiation patterns of the two radiators. Moreover, an additional antenna is adopted to cover WiMAX, WLAN, and Bluetooth services simultaneously in frequency range from 2 GHz to 2.7 GHz.Key words: MIMO, 4G, ECC, Ground Planes, Inductive Coil. Manuscript received February 5, 2013 ; Revised February 27, 2013 ; Accepted March 11, 2013. (ID No. 20130205-006J) Dept. of Electronics and Computer Engineering, Hanyang University, Seoul, Korea. Corresponding Author : Jaehoon Choi (e-mail : choijh@hanyang.ac.kr) This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Ⅰ. IntroductionFourth Generation (4G) mobile communications have received substantial attention, dominating the recent mobile communication market. The Multi-input Multi-output (MIMO) antenna is expected to be a key element in supporting 4G systems [1]～ [3]. Because of the limitation of volume in a mobile terminal, MIMO antennas usually have low efficiency and narrow bandwidth. As the biggest piece of conductor around the antenna in a mobile terminal, the ground plane has aroused much interest. It has been widely accepted that the utilization of a ground plane could substantially improve the performance of small antennas [4]. In the MIMO system, the value of Envelope Correlation Coefficient (ECC) is a key parameter in evaluating the performance of an antenna. In general, a small ECC value guarantees a good isolation performance in a MIMO system. However, isolation is not directly related to the ECC in a MIMO system with small antenna elements because of the low efficiency. So some popular approaches to enhancing isolation performance do not effectively improve ECC simultaneously [5]. The only valid method for improving ECC in a small MIMO system is to increase the pattern diversity of different antenna elements. In a MIMO system with small antenna elements and quasi-omnidirectional radiation patterns, the most effective way to lower the ECC is to increase the separation angle between the different patterns.In this paper, a MIMO antenna designed for 4G mobile application is proposed. By utilizing the resonance of ground planes and an inductive coil, the...

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