Research On Ultra-wideband Antenna And Its Loading Technology

With the rapid development of information technology,the increases of wireless communication devices and users have put new demands on communication systems.Ultra-wideband(UWB)communication has increasingly highlighted its advantages and it has become a research hotspot for improving communication speed and communication capacity.Antennas as basic components of communication systems play an important role,so doing research on ultra-wideband antennas is necessary.For a single-band narrowpulse communication system,the time domain characteristics of the antenna is directly related to the transmission and reception of the pulse signal.For multi-band ultrawideband systems,in order to increase the flexibility of the spectrum and the communication capacity,ultra-wideband antennas with excellent performance have become their demand.In addition,the parameters of traditional antennas sometimes fail to meet the requirements in practical engineering applications.At present,loading technology is widely used in antenna design,and it is an effective way to improve the radiation performance of the antenna by loading special structures on or near the antenna.According to the theory of ultra-wideband antennas and the analysis of the characteristics of ultra-wideband antennas,three ultra-wideband loading antennas were finally designed in this thesis to response to the requirements of different application scenarios of UWB systems,including the selection of ultra-wideband antennas and antenna dispersion analysis.(1)A new type of antipodal vivaldi antenna with distributed parameter loading,which operates from 0.8GHz to 20 GHz,has been designed in this thesis.By loading the sinusoidal and elliptical structures on the edge of the Vivaldi antenna radiating patch,the impedance matching is effectively improved and the bandwidth is broadened.The design also proposes a microstrip to parallel strip wideband feed balun with a logarithmic gradient line structure,so that the antenna portion and the feeding portion can achieve a good broadband matching.(2)In the view of the good wideband characteristics of planar dipoles,this paper proposes a low profile ultra-wideband dipole antenna with an operating frequency of 3 GHz to 10 GHz,covering almost the entire civilian ultra-wideband band.Because of the loading of the metal reflector,the antenna also increases the gain by 3 dB while achieving directional radiation.(3)The bow tie antenna is a type of planar dipole antenna.Because of its good time domain characteristics,it has been widely used in time domain ground penetrating radar systems.In this paper,the bowtie antenna is proposed by loading RC,so that the antenna has good time domain characteristics in a specific working frequency band,especially in the term of good fidelity of the radiated signal and small signal smearing.