Broadband Printed Endfire Antenna Design

With the gradual improvement of wireless communication system technology,people have more and more strict requirements on antenna structure and performance.In radar,tunnel communication,navigation and mine detection applications,broadband,high gain and directivity have become important indicators to evaluate the performance of antenna.Compared with other antennas,the end-fire antenna has the advantages of high gain and good directivity,and has good effect in direction finding and long-distance communication.Conventional end-fire antenna structures include log-periodic antenna and Yagi-Uda antenna.However,the traditional log-periodic antenna and Yagi-Uda antenna are difficult to be integrated due to their large size,so they cannot meet the current actual needs.Therefore,scholars at home and abroad have applied the Yagi antenna principle to the design of microstrip antenna,proposed a variety of microstrip quasi Yagi antenna designs,and conducted extensive research on the narrow bandwidth and large size of microstrip quasi Yagi antenna.Based on the research and study of a large number of domestic and foreign literature,three microstrip quasi Yagi antennas are designed in order to broaden the frequency band of the microstrip quasi-Yagi antenna,reduce the size and improve the antenna gain.The main research contents of this paper are as follows:Firstly,a butterfly double dipole broadband printed end-fire antenna is designed.The impedance bandwidth of antenna bandwidth is improved by introducing the stepped slot line structure and the bandwidth of antenna is widened.Then,butterfly shaped branches are loaded on the floor reflector and double dipole driver to improve the current flow path of the antenna,Achieve the goal of reducing antenna size and increasing bandwidth.Finally,without changing the size of the antenna,parasitic patches are loaded on the upper and lower sides of the seeker to further improve the bandwidth and gain of the antenna by expanding the radiation aperture of the antenna.Finally,the antenna works at 1.56-3.93 GHz,and the gain is5.84-8.5 dB.Secondly,based on the simple feed structure of printed monopole,combined with concave reflector without sharp structure and five elliptical deflectors,a broadband printed Yagi antenna based on monopole excitation unit is designed for S-band.The simulation results show that the working bandwidth of the antenna is 1.98-4.23 GHz,the impedance bandwidth is 75%,and the gain in S-band is 4-8.7dB,which meets the requirements of S-band wireless communication field.Finally,on the basis of the design of the broadband printed Yagi antenna based on the monopole excitation unit,combined with the low refractive index characteristics of metamaterials,a new type of end fire antenna with an split-ring resonators structure is designed by replacing the elliptical director with split-ring resonators structure,which further improves the directivity of the antenna.The operating bandwidth of the antenna is1.86-4.48 GHz,the impedance bandwidth is 87.3%,and the gain in the S-band is 4.5-10.2dB.Compared with the monopole broadband printed Yagi antenna mentioned above,The maximum gain on the S-band has been increased by nearly 2.2dB,and the antenna radiation characteristics are enhanced.