The Research And Design Of Differential-fed Multiband Antennas

Modern mobile communication technology is developing towards the direction of multifunction and integration.Antenna as an indispensable part of the wireless communication system,the research on antenna has also towards multiband,miniaturization and integration.Differential antenna is a kind of antenna which is fed by differential signals,which can direct connect to differential RF front-end and avoids the induce of balun.With advantages of higher integration and smaller cross-polarization compared with traditional one-port antennas.Multiband antenna can cover several frequencies at the same time,with advantages of compact structure and multi functions.And multiband function has become a trend in antenna research.Therefore,differential-fed multiband antennas have a high research value and broad application prospect.This master dissertation is arranged as follows:1.A differential-fed dual-band directional antenna is proposed.The antenna radiators consist of a bow-shaped dipole,a bow-shaped dipole and a long-arm dipole,printed on one side of a substrate.A microstrip line is printed on the other side of the substrate,and different signals are introduced though a pair of coaxial lines to feed the antenna.A reflector is placed below the radiation unit to achieve directional performance.Experimental results show that the antenna covers two bands,2.35-2.55 GHz and 3.19-4.18 GHz.The antenna's gain in 2.4-GHz band is above 8.4d Bi,and in 3.5-GHz band is above 9.0d Bi,with the characteristics of stable radiation pattern,good directivity and low cross-polarization.2.A differential-fed triple-band directional antenna is proposed.The antenna radiators consist of a pair of low-frequency dipole,two pairs of middle-frequency dipole,and two pairs of high-frequency dipole.The antenna excited by an microstrip on the other side of substrate,and a reflector is placed below the radiation unit to achieve directional performance.Experimental results show that the antenna covers three bands,2.33-2.52 GHz,3.24-3.66 GHz and 4.84-6.32 GHz.The antenna's gain in 2.4-GHz band is above 7.8d Bi,in 3.5-GHz is above 7.9d Bi and in 5-GHz band is above 9.0d Bi,with the characteristics of stable radiation pattern,good directivity and low cross-polarization.3.A differential-fed wideband dual-polarized antenna is proposed.The antenna is composed of two perpendicular crossed butterfly-shaped dipoles,and parasitic elements are loaded near the end of the dipole to expand the bandwidth.A microstrip is printed in the gap of butterfly-shaped dipole for feeding the dipole on the other side.A reflector with metal frame is placed under the antenna to improve the radiation pattern.Experimental results show that the antenna has a bandwidth of 72.7%(3.22-6.90GHz).The antenna's gain in the WLAN band and Sub-6GHz 5G band are higher than 7.0d Bi.Based on the previous antenna,A differential-fed triple-band dual-polarized antenna is proposed.Its highfrequency radiator is based on wideband dual-polarized antenna structure,and introduced notch-band by etching gaps on the dipoles.Its low-frequency radiators are composed of two binary arrays of half-waved dipoles,which are placed around the high-frequency radiator,and fed by two pairs of T-shaped power dividers.Experimental results show that the antenna covers three bands,2.36-2.52 GHz,3.27-3.98 GHz and 4.80-6.13 GHz.Its isolation is greater than 30 d B and gain is higher than 8.4d Bi,with stable radiation pattern and good directivity.