A Case Study on Multi-Band MIMO LTE Smartphone Tunable Antenna

• Main Authors: Wen-Yu Lee, 李文裕
• Other Authors: Lin, Hsin-Piao
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/57mxn4

博士 === 國立臺北科技大學 === 電子工程系 === 107 === With the rapid development of mobile communication technology, mobile devices have employed multiple-input and multiple-output (MIMO) multiantenna technology to satisfy increased data throughput requirements. MIMO multiantenna technology has considerably increased the data throughput without requiring additional bandwidth and emissive power. Therefore, this technology is suitable for radio frequency (RF) environments, resulting in smartphones requiring more antennas. The Cellular Telecommunications Industry Association (CTIA) regulated over 70 sets of Long-Term Evolution (LTE) communication channels in the range of 600–3600 Mhz, requiring smartphones to actively change frequencies. Using tunable antenna, mobile devices can switch frequency flexibly and exhibit favorable radiation properties. In this paper, the discussion of the main antenna starts with those that enable frequency switching through tuning. Based on the planar inverted F antenna (PIFA), a frequency switching antenna design is proposed. This paper is divided into the following sections: 1. This paper introduces the PIFA and the basic concept and research background of the frequency tuning. A MIMO LTE smartphone with a tunable antenna capable of switching between frequencies was analyzed to propose practical solutions for related applications. 2. On the basis of conventional designs, a PIFA was designed. The antenna was compatible with current wireless communication channels, including LTE 700, 2300, and 2600 MHz; GSM 850 and 900 MHz; PCS 1900; and UMTS. The antenna structure was mainly a curved PIFA, capable of emitting a frequency of 900 MHz. By curving the bottom half of the antenna against the carrier edge, the antenna’s profile could be lowered. Moreover, to expand the high frequency range of the antenna, an additional branch was added to the lower left section of the antenna. The antenna’s high frequency range could be increased by adjusting the branch length, allowing the antenna to achieve −6 dB of reflection loss when operating in a high frequency range. Additionally, an SP4T RF dial with parallel ground connection was added. The dial was used to control low frequency operations, allowing the antenna to satisfy low frequency (i.e., LTE 700 and GSM 800 and 900 MHz) requirements. The antenna’s main body was 67.2  10  4 mm3, suitable for the limited space in smartphones. 3. The operation frequencies of the sub-antenna include GSM 850 and 900 (824–960 MHz); DCS (1710–1880 MHz); PCS (1850–1990 MHz); UMTS (1920–2710 MHz) and LTE 700, 2300, and 2500 (698–787 MHz, 2300–2400 MHz, 2500–2690 MHz). The antenna combined a meander monopole antenna with a grounding extension branch to establish five resonant modes. Low frequency modes (Modes 1 and 2) covered the operation frequency of LTE 700 and GSM 850 and 900. High-frequency resonant modes (Modes 3, 4, and 5) fulfilled the frequencies used to operate GSM 1800 and 1900; UMTS; and LTE 2300 and 2500. The overall antenna size including the main-antenna was 67.2  10  4 mm3. 4. The main and sub-antenna designs covered all 2G, 3G, and 4G communication channels and were compatible with the smartphone LTE MIMO antenna. The proposed LTE MIMO antenna exhibited excellent −6 dB bandwidth and a complete radiation pattern; the antennas achieved excellent isolation and a favorable envelope correlation coefficient (ECC).