Research On Circularly Polarized Leaky Wave Antenna Based On Substrate Integrated Waveguide

As a type of leaky wave antenna,leaky wave antenna based on substrate integrated waveguide possesses the advantages of substrate integrated waveguide(SIW)and leaky wave antenna,such as planar,low-cost,easy integration with active components,easy feeding and high-gain.Circularly polarized antennas can reduce the impact of multipath interference on the communication system,and can solve the signal mismatch problem caused by the Faraday rotation effect.Therefore,circularly polarized leaky wave antenna based on substrate integrated waveguide has become a promising research field.For practical application,this paper aims to investigate the circularly polarized leaky wave antenna based on substrate integrated waveguide with wide axial ratio bandwidth performance.The main work and innovations of this article are organized as follows:(1)A circularly polarized leaky wave antenna with orthogonal slots based on SIW is proposed,and theoretical analysis and numerical simulation are given.Firstly,by parametric study,the influence of the antenna element parameters on antenna axial ratio is explored.Through theoretical calculation,the explanation of narrow axial bandwidth of the antenna element is given.Afterwards,the period condition of the periodic leaky wave antenna for-1 order harmonic radiation is derived.The periodic leaky wave antenna is simulated with elements arranged periodically.The simulation results are compared with the theoretical calculation results for verification and the cause of error is analyzed.Results show that the proposed circularly polarized leaky wave antenna has an impedance bandwidth of 22.14%(26.1 GHz-32.6 GHz),and the axial ratio at the main beam direction at 28 GHz is 1.95 d B.The 3 d B axial ratio bandwidth of the antenna is 18.8%(26.5 GHz-32 GHz).In addition,the proposed periodic leaky wave antenna can suppress the open-stop band effect to achieve broadside radiation.(2)An standard waveguide-SIW transition for leaky wave antenna feeding at millimeter-wave band is proposed.The-10 d B impedance bandwidth of the transition is33.39%(24.7 GHz-34.6 GHz).The designed planar standard waveguide-SIW transition can be applied to feed SIW antenna at millimeter-wave band.(3)A circularly polarized periodic leaky wave antenna loaded with electric dipole based on SIW is proposed.Firstly,based on the superposition theorem of magneto-electric dipole pattern,a wideband magneto-electric dipole is formed byintegrating a slot on top of the SIW and a pair of electric dipole.A new type of circularly polarized antenna element is formed by introducing a pair of orthogonal electric dipole and broadband phase delay line.In addition,according to the Floquet theory,the period condition for-1 order harmonic radiation is derived and periodic leaky wave antenna is simulated.Results show that the simulated main beam direction of the periodic leaky wave antenna at 28 GHz is 27 degrees backwards while the axial ratio is 0.35 d B.The axial bandwidth of the antenna is 18.8%(26.5 GHz-32 GHz).furthermore,the effect of air layer on the antenna performances in the process of antenna assembling is studied.Finally,the antenna is fabricated and tested,and the measured results are in good agreement with the simulation results.