Study And Design On Compact Wideband And Narrowband Combined Antennas For Spectrum Sensing Applications

With the tremendous growth of modern wireless communications, crowded spectrum and waste of spectrum resources which have limit a variety of wireless technology application become the important issues. In order to improve the utilization of radio spectrum, the concept of "cognitive radio" has been proposed. According to the characteristics and requirements of cognitive radio, antenna should be composed of "Wideband Antenna Unit", which is used for spectrum sensing, and "Narrowband Antenna Unit", which is used for narrow-band communications system. How to analyze and design wideband and narrowband combined antenna effectively, how to reduce the antenna's size without degrading its electrical performance and how to reduce the cost of the antenna's R&D and manufacture are the key techniques in wideband and narrowband combined antenna development. This dissertation focuses on the basic theory and analysis methods. A novel, compact wideband and narrowband combined antenna has been proposed. The main content of this dissertation includes:(1)The concept of cognitive radio and the new requirements are discussed first. The working principle and analysis method of microstrip antenna, the basic principle and type of reconfigurable antenna and antenna diversity techniques are described. These are as theoretical basis for compact wideband and narrowband combined antenna. Useful design guidelines are concluded.(2)Based on these theoretical knowledge, "Wideband Sub-Antennas Unit" as single ultra-wideband(UWB) antenna is studied first. By studying the simplest monopole antenna, a UWB antenna with rectangular and inverted ladder shaped is designed. Then, on the basis of single UWB antenna, the limited space of wideband and narrowband combined antenna coexistence is studied. A compact wideband and narrowband combined antenna with high isolation is designed. Finally, based on this antenna, the problem about the frequency-agile of the "Narrowband Antenna Unit" is studied. A frequency agile wideband and narrowband combined antenna loaded with reactance element is designed and studied.(3)By electromagnetic simulation software IE3D's large number of auxiliary calculations, a simple, compact wideband and narrowband combined antenna and ultra-wideband diversity antenna are manufactured both numerically and experimentally in detail.