Study Of Miniaturized High-efficiency Reconfigurable Antenna

Wireless communication systems are developing rapidly,which make the antennas in high demand for higher performance significantly.Specifically,it requires the antenna to have a miniaturized size,but also have multi-functional characteristics.Considering that the reconfigurable antenna can achieve multiple functions on a single antenna prototype,it gains a lot of research attention.On one hand,it can accomplish multi-functional transmission and reception of different signals simultaneously.On the other hand,it can reduce the number of antenna units effectively.In this thesis,the reconfigurable antennas will be studied for different performance characteristics.The main contents are as follows:? A miniaturizated high-efficiency dual-frequency polarized reconfigurable antenna is presented.The radiator of the antenna is composed of two ring-shaped patches nested in each other to realize the dual-frequency function at S and C bands.By using two slots placed orthogonally to couple feed the radiator in±45° directions,and four PIN diodes to control the on-off of the coupling slots,to the antenna can achieve different polarization states.In addition,the metal floor at the bottom layer reduces the backward radiation,and the substrate integrated waveguide technology is employed to confine the energy within the metal cavity to reduce energy loss and improve gain and radiation efficiency.The antenna structure is completely symmetrical,and the cross-sectional height is 5.8mm(0.056?).The two cross coupling slots and the stacked structure of the radiator are beneficial to the compactness and miniaturization of the antenna structure.The two operating frequency of the antenna are 2.9GHz and 6GHz,and good polarization reconfigurable characteristics can be achieved in both frequency bands.In the two polarization states,the maximum gain at 2.9GHz is 7dBi,the cross-polarization ratio is-30.7dB,the maximum gain at 6GHz is 9.1dBi,the cross-polarization level is about 29.8dB,and the radiation efficiency is higher than 90%.?A miniaturized,high-efficiency antenna with broadside and monopole-like pattern reconfigurability is presented.It consists of an electric monopole radiator and a magnetic radiator which are systematically placed orthogonal to the circular ground plate.The magnetic radiator consists of a capacitively loaded loop(CLL)which serves as the near-field resonant parasitic element,and a monopole which connects to feed structure and a parasitic patch.The monopole-like beam is generated by the electric monopole and the broadside beam is formed by the magnetic radiator.By controlling the only two PIN diodes integrated into the feed structure,broadside and monopole-like beams can be switched dynamically.By ultilizing the near-field resonant parasitic technology to achieve high radiation efficiency while the package size of its radiating elements is electrically small with karad=0.69.A prototype was fabricated and tested.The measured operational frequency is 1.57GHz,the antenna is impedance matched within an overlapping operational fractional bandwidth of 3.8%.The realized gain value of the broadside pattern at boresight is 7.1dBi and the null of the monopole-like pattern is over-28dBi deep,and the radiation efficiency is higher than 75%.In order to achieve better beam reconfigurable effects,and make the antenna more suitable for detection,multi-function and other scenarios,the performance of the 2×2 antenna array is also discussed,to explore the performance of the array's pattern reconfigurability.