Design And Study Of Compact MIMO Antennas

With the rapid development of modern mobile communication technology, the spectrum resources have been becoming scarce increasingly and it's one of the important research problems in the field of communications that how to improve the utilization radio of the spectrum effectively. As MIMO technology can significantly improve the utilization radio of the spectrum and channel capacity without enhancing transmit power or additional transport bandwidth, it has become one of the core technology of the future mobile communication technology development. However, the mobile communication equipment have become smaller and more portable, antennas must co-exist in limit space. The closer the distance between the antenna elements is, the stronger the coupling between each other will be. How to reduce the coupling between the antenna elements has become an urgent problem for antenna engineers.Firstly, this paper analyzes the research background, summarizes the developments of mobile communication systems and MIMO antenna technology, and also summarizes the effective decoupling technologies that have been used in the design of MIMO antennas.Secondly, a dual-band MIMO antenna based on double-side double-strip has been designed. Though the methods of vertical polarization, neutral line and slot structure, the isolation has reached over 20dB in bands of 2.18?2.51 GHz and 3.25?3.96GHz. And in bands of WLAN 2.4GHz (2.4?2.484GHz) and WiMAX 3.5GHz (3.4?3.69GHz),the isolation are higher than 21.5dB and 20.8dB respectively. Both simulation and practical measurement are utilized to validate that the proposed MIMO antenna can meet the requirements.Thirdly, a tri-band MIMO antenna based on small CPW-fed monopole antenna, whose operating bands can cover both the bands of WLAN and WiMAX has been studied. Vertical polarization and parasitic element technologies have been used in the design of the proposed MIMO antenna to reduce the coupling. The isolation in the WLAN 2.4GHz and WiMAX 3.5GHz bands have reached over 22.4dB, while the isolation in the other bands reached over 29dB. The measurement results of the fabricated antenna are consisted with the simulation results, which has proved the validity of the proposed design methodology.Finally, through combining the typical structure of planar monopole antenna and slot antenna, and the design methodology of loading slot antenna on monopole antenna which can reduce the overall size of the MIMO antenna, an ultra-wide band MIMO antenna with the operating bandwidth of 4.6?10.1 GHz has been designed. The isolation higher than 21 dB has been obtained by using the slot decoupling structure and the radiation pattern decoupling method. The simulation and measurement results have verified that the design methodology is feasible.