Research On The Technique Of Hemispherical Beam Wideband Circularly Polarized Antenna

In this paper,the technologies of the broadband,the wide beam(hemispherical beam coverage)and the circular polarization are studied and utilized to design the antenna with high performances.The main work and achievements of this paper are organized as follows.1.The working mechanism of the narrow-side coupling type and the branch-loaded broadband phase shifter is analyzed in detail and the equivalent circuit models of these phase shifters are constructed.To clarify the complementary mechanism of the dispersion characteristics and impedance mismatch characteristics,the graphical method is introduced.Three branch loading phase shifters with 45°,90°,and 135° phase shifter are designed,achieving working bandwidths of 4.63 octaves,3.94 octaves,and 3.94 octaves respectively.Based on the working mechanism of the narrow-side coupling broadband phase shifter,two new types of phase shifters,transmission line type and a lumped element type are designed.The wide operation bandwidths of about 1.78 octaves and 3 octaves are obtained by the two phase shifters separately.It's worth noting that the lumped element type effectively reduces the size of the phaser shifter.2.A circularly polarized antenna based on a cross-printed broadband dipole is designed for Mobile Communication.and the working bandwidth reaches 2.25 octaves.A complementary parasitic dipole is proposed.Some measures such as dipole deformation and loading of a ring cavity are combined to realizing wide beam performance in a broadband.By using the quasi-square coaxial transmission line designed in this paper,the serious radiation interference from network to the antenna is effectively restrained.Furthermore,two hemispherical beam broadband circularly polarized antenna s working in X-band and X-Kuband are respectively designed to meet engineering needs.The related measurements match well with the simulated results.3.The circularly polarized antenna technology with broadband hemisphere beam coverage in millimeter band is studied.In the millimeter wave band,the performance of the antenna is greatly affected by the distribution parameters due to the small physical size,and the dielectric loss is large.a new type of circular waveguide aperture antenna is proposed.The antenna uses a septum circular polarizer to feed the circular waveguide.Moreover,a bottom parabola surface is designed to effectively broaden the beam and improve the stability of the hemispherical beam in the operation band.the double-layer parasitic ring and the annular groove structures are introduced near the waveguide port,which can be equivalent to a magnetic current ring,broadens the beam width further.