| With the development of science and technology,ultra wideband(UWB)theory and technology have being study by more and more people and become mature.Ultra wideband technology has a very wide range of application prospects in production and life:such as the UWB ground penetrating radar(GPR)used in urban construction,national defense,archaeology,environmental protection and so on;UWB synthetic aperture radar(SAR)used for imaging and detection of remote sensing aspects;the short distance and high speed UWB comnunication systems;and other UWB radars for post disaster rescue and vital signs of patients in biomedical field.UWB antenna,as the core component of UWB system,has a crucial impact on system's performance.The UWB antenna not only needs low reflection coefficient and good radiation patterns in the frequency band,but also requires nice time domain performance,such as higher fidelity and less ringing,and so on.This has put forward strict requirements for the design of UWB antenna.Aimed at the above applications and requirements,also on the basis of learning and summarizing a variety of multilayered-stacked UWB antennas,two kinds of UWB antennas are proposed,which are the multilayered-stacked cavity backed UWB monopole antenna and the multilayered-stacked UWB Yagi antennas.The basic structure of the antenna is obtained from the analysis of the antenna model,parameter optimization,and so on.On this basis,an improved antenna is get by adding a reflection or coupling unit.Among them,the size of the UWB cavity backed monopole antenna is 100*100*30mm3,the bandwidth as the S11 better than 10dB is 3?10.5GHz,also the peak gain is 8?13dB,and the antenna can obtain a fidelity value of 0.7 in a wide angle range,and the transient response characteristic is better than the log periodic antenna(LPA).The basic structure of UWB multilayered-stacked Yagi antenna is 3 layers,the bottom floor is the reflector,and the top adjacent to the floor is the broadband bowtie dipole excitation element,and the above is the passive rectangular metal sheet,which is used as the director.The size of the antenna is 60*60*30mm3,the bandwidth as the S11 better than-10dB is 3.4?10.6GHz,and the directivity is 8?11dBi,also the antenna has a stable radiation pattern.The addition of metal plates on the first director can improve the maximum gain of antennas without changing the bandwidth and radiation performance of antennas.After the simulation and optimization analysis,a 6 layer UWB Yagi antenna is made,and its S11 bandwidth and far field pattern are measured.The results show that the simulation is almost consistent with the measurement,and it is within the allowable range of error.The 6 level antenna achieves a fidelity value of 0.8 in the range of 30 degrees near the maximum radiation direction,and its transient response is better than that of LPA.Therefore,these two antennas can be applied to FCC's 3.1?10.6GHz band UWB communication.The two antennas can be used for UWB GPR system,UWB SAR system,medical UWB radar,millimeter microwave application system and so on. |
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