Broadband Circularly Polarized Antenna Design And Array Research

With the rapid development of society,communication is taking a more important role in life.Antenna is an important part of wireless communication.Circularly polarized antenna has the characteristics of resistance to multipath interference,avoiding polarization mismatch,avoiding Faraday spiral caused by ionosphere,etc.compared with linearly polarized antenna.It has been used in satellite positioning,communication navigation and other important applications.The data volume of wireless communication is increasing,the demand for broadband communication system is increasing,and broadband circularly polarized antenna has become the hot spot of antenna research,according to the demand of practical application this paper designs three broadband circularly polarized antennas,which correspond to chapter3 to chapter 5.In Chapter 3,a broadband circularly polarized antenna with an axial ratio bandwidth of92%(2.2-6.0 is designed.The antenna is fed with a coplanar waveguide(CPW)structure and uses eccentric feeds,such as branching outward from the radiating patch and the right-hand metal ground,respectively,to extend the axial ratio bandwidth while spreading the impedance bandwidth to enable coverage(2.0-6.0),and the antenna has a coincident bandwidth of 92%(2.2-6.0).The antenna has a bi-directional radiation pattern,radiating right-handed circularly polarized(RHCP)electromagnetic waves in the positive Zaxis direction.A high-gain CP antenna with an axial ratio bandwidth of 54.9%(3.3-5.8)and an impedance bandwidth of 73.6%(3.0-6.5)is designed in Chapter 4.The antenna consists of a CP microstrip antenna with a wide Z-shaped slot and a non-uniform metamaterial reflector plate placed below the microstrip antenna.The Z-shaped wide slot etched on the metal ground is rotationally symmetric about the center of the antenna,which not only extends the axial ratio bandwidth of the antenna,but also allows to obtain a stable radiation direction map.The surface of the non-uniform metamaterial reflector plate consists of non-equally spaced metal patches,and the length of the metal patches decreases from the right outside to the inside,and the non-uniform metal patch size and non-equally spaced arrangement make the reflector plate have a wide isophase reflection bandwidth.The presence of the reflector plate improves the gain of the circularly polarized microstrip antenna,which makes the antenna as a whole have a stable gain and directional map in the operating band.In Chapter 5,an EM dipole circularly polarized antenna with low profile,high gain and stable radiation pattern is designed.The antenna has an impedance bandwidth of 46.2%(4.33-6.93)and an axial ratio bandwidth of 35.0%(4.53-6.45).The electromagnetic dipole circularly polarized antenna array was designed by embedding metallic copper pillars in the dielectric substrate and,based on this antenna,rotating sequential feeding through a power division phase shift network consisting of a Wilkinson power divider and a phase shifter,and the gain of the antenna was further improved by forming an array,as well as a stable radiation directional map in the operating frequency band.