Design And Implementation Of Ultra-wideband Planar Helical Antenna

With the rapid development of modern wireless communication technology,antenna plays a more and more important role in the military and civil fields.And it is in the direction of multiple devices and multiple frequencies.Therefore,ultra-wideband antenna and its miniaturization design have become one of the most important topics in the field of antenna design at home and abroad.Planar spiral antenna has attracted much attention and developed rapidly because of its remarkable advantages,such as broadband input impedance,circularly-polarized patterns,low profile and easy processing.In this thesis,it focuses on the research of the planner spiral antenna.The thesis mainly studies the millimeter wave applications and low-profile design of the planner spiral antennas.And a novel method of antenna design is proposed in it.The main work of this thesis is as follows:1.Millimeter wave planner spiral antenna:An antenna with a working frequency band of 8?40GHz is designed.It is fed by an exponentially gradual microstrip line-parallel wire balun.Multi section smooth curves are used to improve central feeding structure,and the energy reflection at the feed point is greatly reduced.The antenna shows good wideband character and circular polarization.2.Low-profile planar spiral antenna:An antenna with a working frequency band of 1?4GHz is designed.In this paper,a planner spiral antenna with high impedance surface is applied to reduce the profile height.And an improved high impedance surface is designed to solve the problem of gain loss at high frequency band.Based on the Python,the method of combining the HFSS and the Genetic algorithms(GA)is applied to the automatic optimization design of fragmental high impedance surface element.The high impedance surface designed by the novel method has a more smooth reflection phase curve in the whole working frequency band.The antenna has the height of 0.05*?L(?L is the wavelength corresponding to the lowest frequency of the operating band).