Design Of Broadband Dipole Antenna

The tremendous growth of wireless communication services has led to increasing demand for wide-band unidirectional antennas that can accommodate several wireless communication systems with excellent electrical characteristics such as wide impedance bandwidth, low cross-polarization, low back-lobe radiation, symmetric radiation pattern, stable gain over the operating band and cost effectiveness. As a conventional antenna, dipole antenna has been widely used in wireless communication and radar system because of its simple structure, low cost and stable performance. The Electromagnetic dipole antenna has been developed on the basis of the electric dipole and magnetic dipole, because the electric dipole and magnetic dipole are complementary in space, the electromagnetic dipole antenna has stable radiation patterns in the horizontal plane and the vertical plane.A new magneto-electric dipole antenna was proposed by Luk in 2006. The antenna has not only simple structure, wide bandwidth of 43.8%(VSWR< 1.5), nearly the same identical E-plane and H-plane patterns, low back-lobe, but also stable gain over the operating frequency.In this paper, complementary shorted bridge electromagnetic dipole antenna and complementary split-ring resonator electromagnetic dipole antenna are designed on the basis of the antenna proposed by LUK;An eight-element broadband complementary split-ring resonator electromagnetic dipole antenna array is developed for base station application; finally, a broadband four dipole antenna is proposed. The main contributions of dissertation are summarized as follows:1) Firstly, the background and significance and the research progress at home and abroad of dipole antenna is introduced. Then, the electromagnetic field distribution of electric dipole and magnetic dipole is solved and study the complementarities on the radiation patterns of them. At last, the theory of electromagnetic dipole antenna is put forward.2) Two broadband electromagnetic dipole antennas are designed in this paper: a complementary shorted bridge electromagnetic dipole antenna and a complementary split-ring resonator electromagnetic dipole antenna, the former achieved wide impedance bandwidth of 49.7%, the latter achieved wide impedance bandwidth of 52.4%,The both antennas achieved stable radiation characteristics over the operating band. An eight-element broadband complementary split-ring resonator electromagnetic dipole antenna array is developed for base station application.3) A broadband four dipole antenna is designed; the antenna is balanced feed by the feed network of the coaxial cable and the parallel line. The antenna has a working band from 0.74f0 to 1.3f0 GHz; the impedance bandwidth reaches 54.9%(VSWR< 1.11). The antenna gain is 12 d Bi and no grating lobes appear over the working band. A half-power beam width of 57.4±6.2?and 30±5.7? is achieved in the horizontal plane and the vertical plane.