Improved Dual-Polarized Broadband Antenna Based On Tight Coupling

With the rapid development of communication technology,ultra-wideband communication system has been widely used because of its ultra-wideband,fast transmission speed and other advantages.As the important equipment to send and receive signals,antennas are also asked to have ultra-wideband performance.In this thesis,the design of ultra-wideband current array antenna is studied,while the theory of ultra-wideband CSA antenna is analyzed.The author's contribution is as follow:1.The principle of the increase of the bandwidth about array antennas is introduced based on tight coupling effect among dipole elements.The radiation and feeding structure of the 2×2 current array are improved,in which the commonly concentric feed-type dual-polarized radiation elements will be changed to form a new array.The number of radiation elements has reduced by half compared to the original antenna.The simulation is carried out by using the electromagnetic simulation software HFSS.Simulation results show that the-10 d B impedance bandwidth of the antenna is 110-930MHz(158%).The size of array is 30.5cm×30.5cm×15.2cm.Distance between the antenna element and reflecting plane is 15.2cm,corresponding 1/18 wavelength of the low frequency point.The cross-polarization level of the antenna is less than-30 d B,while the realized gain increases up to about 6d Bi in the operating frequency band.Finally,this 2×2 current array antenna is assembled and tested.The simulated and measured results show good agreement.2.Combined with the equivalent circuit of the tight coupling structure,the model of single polarization infinite current array is simulated and analyzed with ADS and HFSS.Also the influence of different structural parameters on the antenna performance is obtained by parameter scanning.An 8 × 8 dual polarized CSA antenna is designed and simulated by HFSS based on the previous small array.In order to improve the antenna's VSWR parameter in the middle and high band,the methods will be taken such as the load of termination of array,edge resistance and upper layer of the dielectric layer.Simulation results show that the impedance bandwidth is 100-820 MHz with VSWR less than 3,while the radiation patterns show great radiation performance.