Research On The Optimization Design Method Of Quadrifilar Helix Antenna

This paper first briefly introduces the satellite navigation system,and summarizes the origin and development history of quadrifilar helix antenna.The loop-dipole model of quadrifilar helix antenna is derived.According to the derivation,the relationship between the radiation characteristics,polarization characteristics and structure of quadrifilar helix antenna are further obtained,and a new challenge is proposed.Then,based on the definition of the active element pattern,the active element pattern of quadrifilar helix antenna is analyzed,and a new design method for the optimization of quadrifilar helix antenna is presented.It studies the relationship between the amplitude-phase of feed and radiation characteristics,and proposes that radiation characteristics can be optimized by amplitude-phase weighting.In particular,according to different performance requirements,this paper uses optimization algorithm to solve the amplitude-phase of feed of quadrifilar helix antenna on an asymmetric platform.After that,it designs a feed network with weighting function,and presents the active impedance and the matching formula.An antenna for Beidou navigation terminal in the S-band is designed,fabricated,and measured.Finally,based on the work of this paper,the essence of antenna optimization design and its realization process are summarized.This paper is comprised of the followings:First,the origin and development of quadrifilar helix antenna are reviewed,and the optimization theory and algorithm are briefly introduced.Second,the classical loop-dipole model of the quadrifilar helix antenna is derived.According to the conclusion,the radiation mechanism is summarized to compare with the one of spiral antenna.A new challenge for quadrifilar helix antenna is proposed.Third,the active element pattern of quadrifilar helix antenna is presented for far-field radiation characteristics from field and source with the strong coupling between the spiral arms considered.The concept of symmetric platform and asymmetric platform is defined.The negative effect of asymmetric platform on the circular polarization performance of quadrifilar helix antenna is verified by simulation.Fourth,it regards the amplitude-phase relationship between different spiral arms of quadrifilar helix antenna as a degrees of freedom in the design.The amplitude-phase of feed of quadrifilar helix antenna is solved with optimization algorithm to compensation for the effect of asymmetric platform on the circular polarization performance,and then the optimum design for the desired performance is realized.Fifth,according to the design requirements of quadrifilar helix antenna for the Beidou navigation terminal in the S-band,a quadrifilar helix antenna is designed with the optimal design method of quadrifilar helix antenna presented in this paper.Amplitude-phase weighting is implemented by a feed network,and the active impedance and matching problem is analyzed.Finally,it is fabricated and measured.Sixth,the summary of this paper and the following research directon are put forward.