Research On Differentially-Fed Broadband Antenna And Compact Broadband Base-Station Antenna

As a significant component of modern communication system,the performance of base-station antennas has a seriously influence on the quality of the whole communication system.In a modern communication system,through reducing the requirement on other parts,a well-designed high performance base-station antenna can improve the whole quality.As the rapid development of mobile communication system,not only the fourth-generation mobile communication system?4G?is already commercially available,but also the fifth-generation mobile communication system?5G?is about to be put into use.To compat with the second/third generation mobile communication system,high requirements has been put forward to base-station antennas,nowadays base-station antennas should satisfy two basic requirements:firstly,it's impedance bandwidth should cover the whole bandwidth of 2G/3G/4G LTE communication system,secondly,it must have a compact size to adapt to more and more complex scenes.In addition,nowadays differential feeding structure are widely used in RF circuits,and RF front-end devices can be directly integrated with differential circuits.However,most current antennas use single-port feeding structure,so they cannot be directly integrated with differential devices,so if the antenna adopts differential feeds,Balun is no longer needed to connect with differential devices,differential-fed antenna also has common-mode rejection characteristics,thus the differential-fed antenna has an important research significance.The main structure of that dissertation is organized as follows:?I?A broadband differentially-fed multi-dipole base-station antenna with very stable beam-width and intrinsic common mode rejection is presented.The radiator of that antenna is made up of two pairs of dipoles with different lengths.A wide impedance bandwidth,stable half-power beam-width,and good common-mode rejection characteristic features have been obtained by setting the dipoles on two symmetrical cants,and adopting differentially-fed structure.?II?An oval-shaped±45°dual-polarized base-station antenna with wideband characteristics is proposed.By properly setting the feed structure and the parasitic element's parameters,the antenna realized a wide impedance bandwidth with it's S₁₁ less than-15 dB from 1.67 GHz to2.72 GHz,which can fully cover the 2G/3G/LTE band,meanwhile the antenna's isolation is better than-25 dB in that band,and it's half-power beam-width is stable at around 65°in both H plane and V plane.?III?A compact broadband dual-polarized base-station antenna with Y-shaped fed-structure is displayed.The antenna radiator consists of two elliptical ring-shaped dipoles,and four arc-shaped parasitic elements have been embedded between the ring-shaped dipoles.The antenna's VSWR is better than 1.5 within the band from 1.65 GHz to 2.3 GHz,with it's gain larger than8dBi in that band.Because of the presence of two baffles,the half-power beam-width of the H-plane and the V-plane are stabilized at 65°±5°.?IV?A novel compact size,broadband elliptical-shaped dual-polarized base-station antenna is stated.Elliptical bending structure has been adopted in this antenna,which can reduce the overall size of the antenna and meet bandwidth requirement of base station antenna at the same time.The size of it's radiator is only 47.2mm²*47.2mm²?namely 0.346?₀*0.346?₀?,and it's reflection coefficent less than-15 dB in the band from 1.68 GHz to 2.9GHz?with relative bandwidth 53.3%?,meanwhile in that band it also has stable radiation patterns and it's isolation less than-27 dB.