Design And Research Of Several Typical Reconfigurable Antennas

In the modern communication systems, to meet the requirements of communications, navigation, detection and the others, multiple transmitter and receiver antennas have to simultaneously work on a single platform. In this case, more and more load and electromagnetic compatibility among series of antennas become an increasing serious problem to be solved. Reconfigurable antenna, as it can dynamically choose agreeable modes with different environment, achieves a diversity of functions using only one antenna. At present, the reconfigurable antenna is still in experimental research and unable to be used in large-scale commercial application. With the development of switching technology, reconfigurable antenna will usher broad prospects for development.The paper mainly focuses on the theme of the integrated design of reconfigurable antenna and ultra wideband antenna, which aims at improving the utilization rate of the antenna plane and reducing the coupling interference. The research work and main achievements are summarized as follows:At first, the author designs a frequency reconfigurable antenna based on PIN diode. The design integrates the function of ultra wideband antenna with narrow band antenna. Basic method is to place two extra strips in the proper location of the UWB antenna radiating patch, which changes the original current distribution and increases the effective electrical length of the antenna. By switching the PIN diodes ON or OFF, the antenna can work on GSM and UWB mode, WLAN and UWB mode or single UWB mode. Surface current distributions and equivalent circuit model are used to analysis the effects of the added structures. Simulated and measured results show that the antenna has good impedance match and stable radiation patterns across the whole band. The proposed antenna, which integrates narrowband and UWB, will be a suitable candidate for multiband applications and cognitive radio(CR).Secondly, a polarization reconfigurable antenna based on micro-strip patch antenna is designed. In this work, we integrate two different antennas in a same medium plate. The UWB antenna, feed by microstrip line, is printed on the positive side of FR4 substrate. And the microstrip patch antenna that is feed by coaxial probe is fabricated on the back side of the substrate. To separate TM10 mode and TM01 mode, two slots are dug on the radiating patch of microstrip antenna. By selecting different switch state, the antenna can achieve three working modes of linear polarization, left-hand circular polarization and right-hand circular polarization. This method can not only effectively reduce the size and cost of the antenna, but also achieve a high isolation among the various ports which in turn solves the problem of electromagnetic interference.At last, the two designed antenna are successfully manufactured and tested. Reflection coefficient and pattern are obtained using Rohde & Schwarz ZVB20 network analyzer and SATIMO near-field multi-probe microwave anechoic chamber, respectively. Finally, the simulated and measured results match well, which proves the rationality and validity of the design.