Researches On Miniaturized Pattern Reconfigurable MIMO Antennas

In recent years, the wireless transmission business has grown rapidly. Considering the limited spectrum resources, relying solely on the enhancing bandwidth to improve the transmission rate is not realistic. In the wireless communication business, how to maximally improve the spectrum utilization is a hot topic in present research. Multiple-Input Multiple-Output(MIMO) technology can be used to improve the channel capacity of the communication system in rich multipath environments without additional bandwidth or increased transmission power, and it can be used to improve the transmission reliability of the system by increasing the redundancy. In the previous studies of multi-antenna transmission, it is generally assumed that the antenna is a part of the channel, and the antenna characteristic is a non-adjustable parameter of the system. Taking into account the cost in practical application, the antenna selection technique is proposed, which can make the system performance close to the original system by using less radio frequency links.In addition, in order to meet the requirements for large capacity, high speed and multi-function of modern communication, the operating parameters of the system and transmitter often needs to be adjusted according to the change of the surrounding transmission channel. With the development of reconfigurable antennas, scholars have studied the methods of combining the reconfigurable antenna parameters into the channel estimation.In a MIMO system, the capacity of system can be significantly improved by using the diversity of antenna polarization and radiation pattern. By introducing pattern reconfiguration antenna into a MIMO antenna system, the cost can be further reduced and better performance can be achieved. Obviously, the application of reconfigurable antenna in a MIMO system is of great significance. In this thesis, three pattern reconfigurable microstrip antennas are proposed, and a MIMO array is constructed. Detailed performance parameters of the antennas and MIMO array are researched. Brief introduction of the thesis is shown below.Chapter I introduces the background and the topic basis of the subject. The research background and status of pattern reconfigurable antennas and MIMO antennas at home and abroad are given in detail.Chapter II introduces the theories of the microstrip antennas, the basis performance parameters, especially the envelop correlation coefficient, mean effective gain, multiplexing efficient which are used to evaluate the diversity and multiplexing performance of a MIMO system. It’s the basis of the following work.Chapter III proposes three pattern reconfigurable antennas based on the same principle, with each antenna three different beam deflections. Since we choose PIN diodes as the switches to verify the reconfiguration principle, only two different patterns are given.Chapter IV proposes a MIMO antenna array based on the reconfigurable antenna element in chapter III. By simulation and measurement, some parameters such as efficient, envelop correlation coefficient, mean effective gain, and multiplexing efficient are searched, good performance is shown and the antenna can be used in micro base station indoor.Chapter V gives the summary of the whole thesis and the outlook of the future work.