Study On Broadband Dual-band Reflectarray And Broadband Transmitarray Antennas

The high gain antenna has been widely required in modern telecommunication system.However,the traditional high gain antennas have their own shortcomings.Microstrip reflectarray and transmitarray antenna can make up for the shortcomings,which have obvious advantages in structure and performance,such as low profile and plane structure,small volume,light weight,high efficiency,flexible function,low processing costs and so on.This dissertation focuses on the research and design of broadband and dual-band reflectarray,broadband transmitarray and dual-band reflectarray/transmitarray.The details are as follows:1.Develop and analyze of broadband reflectarray antennas.The methods of achieving broadband performance and the restraints of reflectarray bandwidth are summarized and analyzed respectively in this dissertation.Based on the conception of multi-resonant structure,element with phase delay lines and sub-wavelength technique,five novel broadband reflectarray elements are presented,which are the rotating nested hexagon element,the ground slotted element,the four-arm Archimedes spiral element,sub-wavelength multiple-arm Archimedes spiral element and circular ring attached two sets of phase-delay lines element.All of the elements have good reflection characteristics.More than 360? reflection phase range has been obtained with less steep linear reflection phase curves.Besides,the reflection characteristics are insensitive to the incident angle,and more importantly,the reflection phase curves for different frequencies are parallel to each other with good linearity,which indicates the wideband property of the elements.Using the above mentioned elements,several reflectarrays have been designed,simulated,fabricated and measured,and the measured results show good radiation and bandwidth performance.Especially the Archimedes spiral element,which is first being used in the design of a reflectarray,shows an excellent bandwidth performance and high aperture efficiency.In addition,by applying sub-wavelength technique to the Archimedes spiral element,about 500° reflection phase ranges are obtained,which is a significant improvement compared to conventional subwavelength elements.Furthermore,the reflectarray using circular ring attached two sets of phase-delay lines element reach a leading level in bandwidth performance.2.Design and analyze of single-layer dual-band reflectarray antennas.Firstly,an X/Ku dual-band dual-linear polarization reflectarray with two closely separated frequencies has been designed using double parallel dipoles element.The measured results show good radiation performance and high aperture efficiency in both bands.However,the bandwidth of the reflectarray is norrow in both bands.Therefore,six parallel dipoles element is applied to design an offset-fed dual-band dual-polarization reflectarray.A better bandwidth performance has been achieved compared to the double parallel dipoles reflectarray.Thirdly,the feasibility analysis of using double ring element to achieve dual-band operation is performed.sub-wavelength technique is referred and reasonable element lattice period is set.Then a Ku/Ka dual-band reflectarray with two widely separated frequencies is designed.Lastly,a nested ring attached phase-delay line element is proposed and an X/Ku dual-band reflectarray with two closely separated frequencies is designed,fabricated and measured based on sub-wavelength technique.3.Develop and analyze of broadband transmitarray antennas.Based on the design methods and ideas of broadband reflectarray elements,two novel broadband transmitarray element structures,which are three-layers ring attached phase-delay line element and four-layers ring attached two sets of phase-delay lines slot element,is presented in this dissertation.More than 360? transmission phase ranges with small transmission loss are obtained,which show good transmission characteristics in both elements.Besides,the incident angles have little influence on the transmission characteristics of the elements.Two transmitarrays are designed using the elements and simulated results show the good radiation and bandwidth performance.4.Design and analyze of reflectarray/transmitarray antenna.Based on using FSS to design dual-band reflectarray,a dual-band reflectarray/transmitarray antenna which can operate in reflection mode and transmission mode simultaneously is presented.The antenna works as a reflectarray at 13.85 GHz and transmitarray at 8GHz.Both simulated and measured results show good radiation performance in the two modes.The antenna has great potentiality in frequency reuse technologies.