Multi-antena Design And Research Of MIMO System

MIMO of multi-antenna technology has been widely used in various wireless communication system terminal, the key technologies of MIMO multi-antenna design are achieving low mutual coupling, low correlation and miniaturized. Based on the design requirements of MIMO multi-antenna technology, this paper developed several MIMO antennas which applying in the wireless communication system.Firstly, based on the micro-strip log-periodic antenna theory and design method, the author developed a broadband dual-polarized MIMO log-periodic dipole array. Log-periodic dipole antenna with a non-frequency-dependent properties, their design rules are simple and flexible, this paper by selecting the appropriate ratio parameters, through the software simulation and optimization, then obtained the antenna unit which working frequency range is 2-15 GHz, and through the combination of antenna structure, the author obtained a wideband 4 × 4 MIMO antenna. The overall design process is simple,and the proposed antenna has a good directionality and suitable in the field of ultra-wideband antenna applications.Secondly, on the basis of log-periodic dipole antenna designing, the author developed a dual-band dual-polarized MIMO log-periodic dipole antenna array. Which the unit antenna is a two antenna elements of log-periodic dipole antenna, each array element is achieving a resonance frequency, and finally realizing the working center frequencies of 2.4 / 5.5 GHz.The antenna array have a total antenna units of 12, which six horizontal antenna elements are rotating printed in sequential on the substrate board, the angle between the antenna elements is 60 °. Further, the other six vertical antenna elements are sequentially embedded in the substrate plate through the slots, the angle between the antenna elements is also 60 °. Through the combination of structure, completed a 6 × 6 dual-band dual-polarized MIMO antenna array, the antenna array has a very high degree of isolation, the entire pattern can cover the whole three-dimensional space, which is suitable for WLAN wireless communications applications.Thirdly, according to the principle of miniaturized antenna design, the author finished a very compact MIMO antenna, which is suitable for working in WiMAX, IEEE 802.11 a / b / n / g, UMTS, LTE-2300 and LTE-2500 wireless communication system. In order to obtain low coupling between the two antenna ports, first of all, the author cutted a slot on the antenna ground which can cut off the current path nearby the two antenna ports, then achieving a certain dropping of coupling effect, and the H-shaped stub structure is loaded into the middle groove, by optimizing through the computer software,achieving a further reduction of coupling effect.Finally,the author have designed a kind of MIMO antenna which working center frequency is 2.45 GHz, this antenna’s frequency range is 2.4-2.5 GHz and the isolation is less than-20 dB,the correlation coefficient is less than 0.02,which is suitable to WLAN wireless applications.