Endfire Circularly Polarized Antenna And Calculation Method Based On Periodic Structure

The periodic structure is an infinitely long transmission line or waveguide loaded with reactive elements,which can be made into various forms related to the nature of the transmission line or waveguide used.The discontinuity caused by this periodic loading can be simulated on the equivalent circuit as the lumped reactance periodically connected across the uniform transmission line.The slow wave and passband-stopband characteristics provided by the periodic structure make it versatile.There are many common methods to analyze the dispersion characteristics of periodic structures,including theoretical analysis method,eigenmode method and unwrapping method based on electromagnetic simulation software,et.,which have different advantages and disadvantages.This paper presents a method for calculating wave propagation constant,reflection coefficient and wave impedance based on electromagnetic simulation software,which is derived from field distribution.The main work of the paper includes:1.A method for calculating the dispersion characteristics of waves in periodic structures is proposed-field distribution based method(FDBM).This method is based on the relationship between the electric field or the magnetic field at each point in the periodic structure,then derives the theoretical formulas about the characteristic parameters.Finally,the propagation constant(attenuation constant and phase constant)of each point in the structure is calculated and the dispersion characteristics of the periodic structure is obtained.This calculation method was verified in different periodic structures such as uniform waveguide,waveguide loaded periodic metal diaphragm and leaky-wave antenna,then the results obtained by FDBM were compared with those obtained by other known methods to verify its applicability.2.A planar end-fire circularly polarized antenna using periodic structure is proposed.The vertical polarization is generated by the H-plane horn based on SIW,and the horizontal polarization is generated by the periodic metal curve.A planar end-fire circularly polarized antenna with a center frequency of 20 GHz is realized.Its beam is parallel with the dielectric substrate plane and the maximum realized gain is 7.1d Bi.3.A wideband planar end-fire circularly polarized antenna for 5G(24.75GHz-27.5GHz)application is proposed.On the basis of the former antenna,the bandwidth of the antenna can be widened by changing the periodicity of the periodic curve which provides the horizontal polarization.Finally,a wideband planar end-fire circularly polarized antenna with 34.8%impedance bandwidth and 10.6% axial ratio bandwidth is realized.The beam is parallel with the dielectric substrate plane,and the maximum realized gain is about 7.7dbi.