Research On Ultra-wideband Feed Antenna Of Radio Telescope

With the increasing demand for sensitivity,observation field of view and observation bandwidth of radio telescopes,a new generation of telescope solutions has been proposed.The Square Kilometre Array?SKA?is the world's largest integrated aperture radio telescope currently planned to be built internationally,and it will be 50 times more sensitive and 10,000times faster than the existing maximum radio telescope array?JVLA?.The first stage of SKA consists of a mid-frequency reflector antenna array and a low-frequency aperture array.The mid-frequency array has the widest band coverage?0.35-13.8GHz?and the highest sensitivity and resolution,the performance of it is critical to SKA.As the core component of the reflector antenna system,the feed affects the comprehensive performance of the radio telescope directly.At present,ultra-wideband feed has become the main technical bottleneck for radio telescopes to achieve broadband observation.Therefore,the research on ultra-wideband feeds is of great significance for both radio telescopes and radio astronomy.Based on the full understanding of the research status of broadband feed technology,this paper studies two feeds with high broadband comprehensiveness performance,namely log-period circular dipole array?Eleven?and Quadruple-Ridge Flared Horn?QRFH?,from working principle,modeling and simulation to parameter optimization,performance analysis.Aiming at the problem of complex structure and difficult optimization of the ten-octave circular Eleven antenna,this paper uses the improved genetic algorithm composed of improved selection operator,adaptive crossover and mutation operator to optimize a 6-14GHz circular Eleven model by MATLAB-CST co-simulation,based on the traditional genetic algorithm to optimize the reflection loss performance of broadband feed.Then,according to the non-frequency-changing structural characteristics of the log-period antenna,the optimization model was directly extended to obtain a 0.95-14GHz full size ultra-wideband circular Eleven feed.The research results show that the improved genetic algorithm improves the optimization efficiency and optimization precision.Moreover,since a optimization model closer to the full model is selected,the reflection loss of the full-scale ultra-wideband Eleven feed obtained by the final expansion is reduced by more than 1.5dB.In addition,the circular Eleven feed has good radiation characteristics and an average aperture efficiency of up to 70%.Aiming at the problem that the phase center of the horn antenna varies greatly with frequency and the aperture efficiency of high frequency band is poor,this paper studies and designs a QRFH ultra-wideband feed operating at 4.6-13.8GHz based on the ridge waveguide theory.The reflection coefficient of the feed is lower than-10dB in the working bandwidth,the directivity coefficient is higher than 9dBi,the phase center is relatively fixed,the radiation characteristic is relatively stable,and the aperture efficiency is higher than 50%.It is worth mentioning that the₁₁ and₂₂ of the feed are better than-10dB and-7dB in the ultra-wide bandwidth of 4.6-24GHz,respectively,which means that it has the potential to be the ultra-wideband feed solution of the band B of WBSPF?Wideband Single Pixel Feeds?in SKA advanced instrument project.