| With the rapid development of wireless communication technology,under the emergence of new technologies,high standards and requirements for antenna performance and size have emerged.In the context of stringent communication technology requirements,MIMO wireless communication technology stands out.Its working principle is the combination of diversity and multiplexing.In other words,it optimizes the transmission,reception and multipath wireless channels.The advantage of doing so is that it can not only ensure the signal has a high transmission rate,but also maintain high transmission quality without taking up extra bandwidth.The pattern reconfigurable antenna can dynamically adjust its radiation pattern according to the changes of the external environment,and enhance the capacity and security of the whole system to a higher level.If the MIMO system and pattern reconfigurable antenna technology can be combined,the size of the whole system can be compressed to a large extent,and the extra cost can be avoided,and the performance of the whole system can be improved.In this paper,two kinds of reconfigurable antennas with different patterns are designed and the MIMO array antenna is composed.Firstly,a Reconfigurable Microstrip Antenna with a working frequency band of 2.4 ~ 2.5GHz is designed.The antenna structure includes a main radiation patch and a PIN diode loaded on the surface of the parasitic patch.The surface current of the parasitic patch can be redistributed with the on-off state of the switch.By turning off or closing the diode switch,the antenna can present different working states,which are directional and omnidirectional.In order to simplify the experiment,the on-off of the PIN diode switch is replaced by copper.By switching the diode switch,two kinds of directional pattern and omnidirectional pattern with different main beam deflection angles are realized,among which the directional deflection angle is 180 °.Secondly,a pattern reconfigurable antenna based on a Yagi antenna is proposed.In order to solve the problem that the traditional Yagi antenna is too large,this paper designs a miniaturized dual-frequency pattern Reconfigurable Microstrip Antenna II by using the loaded inductor.The pattern of the antenna is reconstructed by loading a PIN diode switch between the exciter,the ground plate and the microstrip feeder.The whole structure of the antenna is compact,with 2.3-2.6GHz and 5-5.9GHz working for frequency bands.In order to simulate the working environment of PIN diode switch,resistance is used when the switch is closed,and capacitance is used when the switch is open.When the different side of the vibrator is excited,the antenna will produce a pattern of the equal amplitude deflection angle of 180 °.Finally,a dual-frequency pattern reconfigurable MIMO antenna array is constructed by using the pattern reconfigurable antenna II proposed in the previous chapter as the reconfigurable element.The whole MIMO structure is composed of dual-frequency pattern reconfigurable microstrip antennas loaded with PIN diode switches,which are arranged in an orthogonal way.By turning on or turning off the PIN diode switches,the MIMO array completes the radiation beam deflection in different states.Due to the limited experimental resources,only five groups of simulation and test results are given. |
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