The Analysis Of Ultrawideband Antenna Array Based On Tightly Coupled Dipoles And Patches

Ultrawideband(UWB)phased array plays an increasing important role in modern wireless communication and remote sensing systems.Wideband beam forming front ends is required in advanced radars,software-defined radios,electronic interfere measurement and radio telescope.As one of the new types of UWB antenna array,tightly coupled antenna array utilizes mutual capacitive coupling between elements to counteract the effect of inductive backplane.Therefore,the challenges of suppressing mutual coupling in phased antenna array have been addressed with this method.In this thesis,the main focus is to design a ultrawideband antenna array with integrated feeding method.Firstly,a general analysis of planar periodic array is given based on the Floquet theorem.According to the model of current sheet array,we have studied the close relationship between tightly coupled antenna array's physical model and equivalent circuit.This former study provides instructive guidance to shapes and dimensions of proposed TCA array.Based on the previous theoretical study of TCA array,we propose a dual-polarized tightly coupled antenna array with EBG substrate loaded.The bandwidth of antenna array is from 900 MHz to 9GHz(10:1).Besides,we have studied the effects EBG substrate and absorptive layers to reflection coefficient and radiation efficiency.The results show that the substrate loading of EBG could overcome the short circuit effect of PEC backplane.The TCA array's bandwidth is doubled for this method.The radiation efficiency of total array is close to 80% and cross-polarization isolation is nearly 40 dB.We have varied this result from simulation of this dual-polarization unit cell.In the end,we have researched into the feeding techniques of tightly coupled antenna array.We propose the TCA array with integrated feeding method.The absorptive resistive layer(AFSS)is applied to suppress short-circuit effect of PEC plane.The dielectric superstrate is used as wide angle impedance matching layer(WAIM)to avoid blind spot in scanning angles.The TCA-IB array works from 2GHz to 10GHz(5:1),the beam could scan in a range of ?45?.The measured maximum gain of array is close to ideal gain and the cross-polarization isolation is close to 20 dB.The proposed array have the benefits of integrate feeding baluns with array's elements.Thus,the array is low-profile,lightweight and miniaturized structure.We have given the experimental test of the proposed TCA-IB array and give a comparison between simulated and experimental results.