Design Of Miniaturized H-Plane Circularly Polarized Horn Antenna Based On Field Redistribution On Radiation Aperture

In the depolarizing medium and multipath propagation environment,circularly polarized（CP）antennas can improve the polarization mismatch problem,which are widely applied in the wireless communication systems.Horn antennas have the advantages of simple structure,wide bandwidth and high gain,which make the technology of CP horn antennas gain wide attention.Substrate integrated waveguide（SIW）has the advantages of compact structure and easy integration with the planar circuits.By utilizing the SIW structure to design CP horn antennas,the features of low profile and light weight can be attained.Two miniaturized H-plane CP horn antennas of metal type and substrate type are studied and designed in this thesis.By loading the antipodal tapered slots,the electric field component orthogonal to the direction of initial polarization can be attained in the horn antenna.The metal blocks or metallized blind holes are inserted into the flared part of the horn antenna to correct the electric field distribution on the radiation aperture and optimize the amplitude difference and phase difference of the two orthogonal electric field components.Finally,the satisfied CP radiation performance can be achieved in the miniaturized H-plane horn antenna.The specific work is carried out as follows:First,a miniaturized H-plane CP horn antenna of metal type based on the antipodal tapered slots and metal blocks is designed.At the beginning,a wideband optimum H-plane horn antenna of metal type based on the design rule of optimum horn antenna is designed.By loading the antipodal tapered slots on the broad walls of the optimum horn antenna,the electric field component orthogonal to the direction of initial polarization is attained.A pair of orthogonal polarized radiation fields with equal amplitudes and 90°phase difference is obtained and the wideband CP horn antenna is achieved.In order to achieve the miniaturization characteristic in the CP horn antenna,the longitudinal profile of the horn antenna is shortened and the metal blocks are loaded inside the flared part of the horn antenna to correct the field distribution on the radiation aperture.Finally,the equal amplitudes and 90°phase difference of the two orthogonal electric field components are attained again,and the satisfied CP radiation performance is achieved.The proposed antenna is fabricated and measured.The results show that the CP operating bandwidth is32.8%（11.35-15.8 GHz）and the gain range within the CP operating bandwidth is from8.34 to 10.24 d Bic.The longitudinal length of the proposed antenna is 1.36λ₀,which is reduced by 33.3%compared with the original CP horn antenna.The satisfied CP radiation performance and miniaturization characteristic are achieved in the proposed antenna,verifying the validity of the design.Second,a compact SIW H-plane CP horn antenna based on the antipodal tapered slots and metallized blind holes is designed.At the beginning,an optimum H-plane horn antenna is designed based on SIW structure.By loading the antipodal tapered slots on the upper and lower metal floors of the horn antenna,the electric field component orthogonal to the direction of initial polarization is attained.The metallized blind holes are loaded inside the flared part of the horn antenna to correct the field distribution on the radiation aperture.The equal amplitudes and 90°phase difference of the two orthogonal electric field components are obtained.Finally,the satisfied CP radiation performance is achieved in horn antenna.The proposed antenna is fabricated and measured.The results show that the CP operating bandwidth of 6.69%（15.9-17 GHz）is attained and the gain range within the bandwidth is from 6.49 to 7.38 d Bic.The satisfied CP radiation performance is achieved in the proposed antenna with the features of compact structure and light weight,verifying the validity of the design.