The Deign And Realization Of Pattern-Reconfigurable Antenna System

Recently, with the rapid development of wireless communication technologies, wireless communications make higher and higher demand for antennas with good performance. The research on reconfigurable antennas has become a hotspot gradually in the antenna filed, because they can adjust their characteristic parameters such as frequency, radiation pattern and polarization, according to the real environment. In this thesis, to form a pattern-reconfigurable antenna system, the elements of antenna array, feed circuits and control circuits have been systematically studied on the basis of existing literatures. The design processes of every parts of the system are given in details. Finally the antenna system is fabricated and measured. The test results show that, the designed pattern-reconfigurable antenna system has 360-degree coverage in azimuth in the band of 2.4GHz-2.48GHz.This thesis is divided into six parts.Firstly, the paper states the significance and status of the research on reconfigurable antennas, introduces the electromagnetic simulation software used, and summarizes the beamforming technologies for pattern-reconfigurable antennas.Afterwards, elements of the antenna array and feed circuits are analyzed and studied. Based on the 4-Yagi antenna, a novel 3-Yagi antenna is proposed, with the advantages of smaller in size, lower back-lobe level and wide bandwidth. The antenna elements are fabricated and measured as well as those with switching circuits, to verify the designs.Then, according to the reasonable structure, an antenna array is formed with six elements, three 3-Yagi antennas and three 4-Yagi antennas. The simulation results show that, the 3dB beam width of the array can cover 360 degree in azimuth.After that, the control circuits are designed. The circuits can output signals with different levels according to the program. With the high level signals, the PIN diodes in switch circuit are driven. And then, based on simulation, the antenna array integrated with feed circuits and the control circuits are fabricated respectively and also measured in the appointed beam scanning mode. According to the measurement, the designed pattern-reconfigurable antenna system covers 360-degree in azimuth, the coverage of which is wider than that of the antenna array proposed in the literature.Finally, the thesis summarizes the entire work and gives the future prospect of the relevant research work.