Research On Key Antenna Technologies In High-speed And Long-distance E-band Communication System

In order to achieve ultra-high-capacity wireless communication,the working frequency is moving towards higher frequency band to obtain more available bandwidth.The E-band(71-76/81-86 GHz)permitted by the International Telecommunication Union(ITU)can provide 10 GHz available bandwidth.E-band is in the atmospheric window,and the atmospheric loss is less than 0.5 dB/km.Therefore,it is suitable to establish fiber-equivalent-speed and long-distance wireless data links in E-band.Also,with the development of high-power active devices and high-speed baseband technology,it is time to develop the licensed E-band spectrum.Under the background,the author has carried out a series of researches on reflectors and feed antennas in E-band high-speed and long-distance wireless systems for different application requirements,mainly including the following research contents:1.For E-band air-to-ground/air-to-air wireless applications,a reflector antenna in the front end of the airborne side or the satellite side has been developed.The antenna has the characteristics of both high aperture efficiency and adjustable beamwidth.The high aperture efficiency can maximize the gain of the transmitter antenna in the limited space of the air platform,and the adjustable beamwidth can lead the transmission distance of the E-band wireless link with a higher dynamic range.The link budget method of E-band communication is summarized and analyied,and the antenna gain requirement for high-speed long-distance E-band wireless link is calculated.Based on this budget,an E-band high aperture efficiency reflector antenna with adjustable beamwidth is developed.A method is proposed to improve the aperture efficiency of the entire reflector antenna by slightly shaping the sub-reflector.The defocusing effect is used to effectively increase the beamwidth of the reflector antenna,and the halfpower beamwidth(HPBW)is adjusted by axially moving the sub-reflector.After shaping optimization,the aperture efficiency is increased to about 75%.The measurement results show that from 71 to 86 GHz,the realized gain is 45.6 ± 1 dBi,and the HPBW can be increased by more than 5 times.2.The polarization multiplexing technology is an effective way to improve the spectral efficiency and the capacity of the communication system.The orthomode transducer(OMT)is the key divice in polarization multiplexing technology.Based on this background,a novel double-ridged OMT is firstly proposed.After analyzing the mode separation principle,we improved the traditional structure.By length reducing of ridges in the square waveguide,the ridge width of proposed junction is about three times wider than that of conventional junction.This benefits the fabrication and mechanical performance of double ridged waveguide OMT in the higher mm-wave band or terahertz band.The simulated reflection coefficients for both orthogonal modes are less than-20 dB over 37%bandwidth.Based on this structure,an E-band OMT based on the novel junction is fabricated.A smooth-horn is integrated with the OMT as a dual-polarized antenna.The measured results show that reflection coefficients less than-15 dB,isolation better than 39 dB,cross-polarization discrimination(XPD)higher than 23 dB are achieved from 71 to 86 GHz.On the basis of the dual linearly polarized feed,a circular polarizer is inserted to realize a dual circularly polarized feed antenna,and an axially displaced elliptical reflector antenna is loaded to achieve both high gain and dual circular polarization performance.The realized gain of 45 ± 1.2 dBi is obtained.The measured axial ratio(AR)of dual circular polarization is less than 2.3 dB.The measured radiation pattern is consistent with the simulation results.3.The dual-band communication is a key technology that takes into account high speed,long distance and high availability of wireless link.The microwave channel and the millimeter-wave channel can form a mutual protection mechanism.Based on this background,a dual-band multi-polarized feed antenna is proposed.By adopting the coaxial hybrid feeding,the antenna can radiate microwave and millimeter wave in the same aperture.Four chokes are inserted in the coaxial waveguide to improve the the TE11 mode wave matching with the free space,so that the feed antenna has good return loss in both microwave and millimeter-wave bands.Integrating advanced feed technology,microwave and millimeterwave channels can realize polarization multiplexing,respectively.The horn aperture adopts the coaxial corrugated form,which introduces more degrees of freedom in the design.By optimizing the dimensions of corrugations,similar rotationally symmetric radiation performance at Kband and E-band can be obtained.The measured reflection coefficients of two microwave ports are both lower than-15 dB,and the isolation is higher than 50 dB.The reflection coefficients of two mm-meter ports are both lower than-15 dB,and the isolation is higher than 24 dB.4.Commercial SoC modems in the E-band typically support a maximum bandwidth of 2 GHz.In order to realize the maximum capacity of the communication system based on commercial modems,the communication capacity can be extended to 4 times that of single-chip modems through frequency multiplexing technology(71-73/74-76 GHz)and polarization multiplexing technology(LHCP/RHCP).Based on this background,the method and structure of the simplified RF front-end are given,and a compact duplex dual polarizer for the system is proposed.The duplex dual polarizer is composed of a turnstile junction and a four-channel iris filter.Compared with the traditional solution to realize the duplex dual polarization,the duplex dual polarizer has an ultra-compact structure with good electrical performance,and the size is only 5λ×5λ×0.75λ.The simulation results show that the reflection coefficients of the four WR12 waveguide ports are all lower than-10 dB,the insertion loss is lower than 0.5 dB,and the isolation of the orthogonally polarized ports at the same frequency is higher than 25 dB.Finally,a circularly polarized horn antenna with a slot on the inner wall is designed.Combine the duplex dual polarizer with the circularly polarized horn antenna to realize a duplex dual circularly polarized antenna for the front end of the multiplexing system.