Research On The Ultra-wideband Dielectrically Loaded Quad-Ridged Flared Horn Feed

With the development of radio astronomy technology,wider frequency band and higher efficient design requirements are proposed for the reflector antenna and wideband feed need to be developed.The Quad-ridged flared horn(QRFH)feed has the advantages of simple feeding,controllable beam width,and high aperture efficiency,becoming a hotpot in the research of wideband feed.However,the QRFH is restricted by the problem of the low efficiency at the high-frequency,so its operating bandwidth is difficult to exceed 7:1.In the thesis,the QRFH is loaded with a dielectric rod to concentrate energy,reduce the radiation aperture,broaden the beam width,improve the antenna aperture efficiency at the high-frequency,and broaden the operating bandwidth.The detailed work is shown as follows:(1)In the dielectric waveguide,the field and the modes distribution are analyzed.In the dielectric loaded waveguide,the influence of frequency and dielectric radius on the energy in the medium is analyzed.The analysis results show that the high frequency energy in the waveguide can be gathered in the dielectrically loaded.(2)The simple QRFH model and the dielectric-loaded QRFH model are established.The effects of each geometrical parameter on the transmission and radiation characteristics of the QRFH are studied,which lay a theoretical foundation for the design of the dielectric-loaded QRFH feed.(3)The design ideas and steps of dielectrically loaded QRFH feed are proposed.Based on these design ideas,the designs of two dialectically loaded QRFH feeds are completed.The single layer dielectric-loaded QRFH has a VSWR less than 2:1 and aperture efficiency more than 50%from 1.5 to 15GHz.The double layers dielectric-loaded QRFH has a VSWR less than 2.5:1 and aperture efficiency more than 50%from 1.35 to 18GHz.(4)A dielectrically loaded QRFH feed prototype was developed and tested.The test results show that the VSWR is less than 2.5:1 and the beamwidth in the E and H plane are stable and almost same for the continuous bandwidths up to 13.3:1(1.35-18GHz).The measured radiation patterns are in good agreements with the calculated ones,which verify the validity of the analysis and design method.Its working bandwidth is 13.3:1,which is much higher than the current literature reports.