Research On The Mobile Terminal Loop Antenna And MIMO Multi-antenna Decoupling

With the rapid development of wireless communication technology, the design of mobile terminal antenna is confronted with great challenges. Because electronic products are highly integrated, the space for antenna is smaller than ever, which requires that the antenna be designed into plane structure and be smaller as well. On the other hand, the coexistence of various communication modes also requires that the working band of antenna be wider. It is very difficult to solve these problems by traditional antenna design technology. Besides, MIMO technology provides good technical support for approaching the scarcity of spectrum resources, but it is difficult to be applied to the mobile terminal. The reason is that the introduction of multi-antenna will inevitably lead to the decrease of space for each antenna; the strong inter-antenna coupling will undermine the performance of the antenna array itself. In order to meet the goal of mobile terminal applications in 5G communication systems, this dissertation studies miniaturization, multi-band and multi-antennas by choosing loop antenna of multi-resonance mode, monopole antenna and defected ground structure, thanks to the sponsorship of “Hong Kong, Macao and Taiwan Science and technology cooperation projects” entitled “The fifth generation mobile communication wireless access technology research and verification”. The main contents and results are as follows:1. A miniature loop antenna for mobile handset is proposed based on the characteristic of multi-resonance mode, which enables the extension of current path by meandering loop line. The antenna is printed on a FR4 dielectric plate and connected to the folded micro-strip line on the back side with four short-cut points. At low band, matching circuits are loaded to improve the impedance bandwidth with a new point of resonance formed at the same time. The high band is achieved by folded micro-strip and the higher-order resonance mode of loop antennas. The designed working bands are: low bands(730MHz~960MHz) and high bands(1.59GHz~2.86GHz), covering eight communication bands, including GSM850, GSM900, GSM1800, GSM1900, UMTS, LTE2300, WLAN2.4GHz and LTE 2500.2. A wideband decoupling method is designed based on decoupling mechanism of defected ground structure. The method is to etch three pairs of open-ended slots with variable length on a T-shaped metal ground to form a pair of L-shaped monopole branch and two pairs of I-shaped monopole branch. The whole antenna array is also printed on both sides of the FR4 substrate. The designed bands are: low bands(685MHz~760MHz, 910MHz~960MHz), high bands(1.65~2.53GHz), covering: LTE700, GSM900, GSM1800, GSM1900, UMTS, LTE2300, WLAN2.4GHz. The minimum distance between edges of antenna units is 6mm, and the isolation degree is above 15 dB at all working bands.