Research On Miniaturized Antenna With Directional Radiation Characteristics

Multi-antenna system are often applied in communication equipment to achieve multiple requirements,while the multi-antenna system requires a large amount of equipment and space resources.In order to realize good radiation performance in a limited space,the accelerated demands have driven antenna to be miniaturized and multi-functional.In the fields of long distance communication,intelligent traffic and radar system,directional antenna is widely applied due to its performance of high gain in a certain direction,which can increase the effective utilization of radiation power as a transmitting antenna,and increase the anti-interference ability as a receiving antenna.Moreover,the miniaturized directional antenna has advantages of good directivity and small size,which provides possibilities for systems to be more compact.In this thesis,the requirements of miniaturized directional antennas in different scenarios are focused on,combined with quasi-Yagi principle,Huygens sources and reconfigurable technologies,to improve directivity,expand bandwidth and realize patternreconfigurable and conformal characteristics of miniaturized antennas.The main contents of this thesis are as follows:Firstly,this thesis introduces the research background and significance of directional miniaturized antenna,investigates the research status,clarifies the concept of directional radiation characteristics,and illustrates the design principle of quasi-Yagi,reconfigurable and Huygens source as well as antenna miniaturized method.Secondly,according to the communication requirements on the surface of the flying object,a directional single-layer miniaturized antenna was designed based on the quasi-Yagi principle and the simulation analysis of the surface current distribution.By mounting the uniplanar antenna conformally on a cylindrical structure,it is demonstrated numerically and experimentally that its end-fire radiation performance characteristics are maintained.Thirdly,in order to meet the requirements of real-time variable beams in the intelligent traffic system(ITS)and solve the narrow bandwidth problem of the miniaturized antennas,a wideband pattern-reconfigurable flexible miniaturized antenna has been designed in combination with a flexible substrate,quasi-Yagi principle and reconfigurable technology.Simultaneously,the two opposite radiation patterns are switched in real time through electrically controlled PIN switch diodes,and stableend-fire radiation performance characteristics are maintained within the working frequency band in the case of planar and conformal conditions.Finally,for indoor wireless communication applications,a pattern-reconfigurable Huygens source miniaturized antenna is designed.Combining Huygens source and reconfigurable technology,the designed electric NFRP and magnetic NFRP are placed orthogonally to excite the same current amplitude with a similar center phase.A well-radiated Huygens source end-fire radiation pattern is formed.At the same time,three PIN switch diodes are loaded on the electric NFRP to form three pattern-reconfigurable states,and the scanning beam can achieve full coverage of the azimuth plane.