Design Of Broadband Circularly Polarization Microstrip Slot Antenna

With the rapid development of science and technology, the requirements for the performance of antennas become higher, especially in the wider bandwidth, smaller volume, more functions and higher efficiency. Therefore, the research of wideband and circularly polarized antenna has become an important topic in the field of the antenna.Based on the theoretic analysis, a study is made on wide-band and circularly polarized slot antenna. The author’s major contributions are as follows:Firstly, a broadband circularly polarized microstrip slot antenna is designed. Coupling feed structure is realized by adopting microstrip line with H-shaped crossed orthogonal slots. It can excite two linear polarization electric field components with equal amplitude and a phase difference of 90 degrees, resulting in radiating circularly polarized waves. In order to increase the bandwidth effectively, a resonant circuit may be formed with a double square patches. The proposed antenna exhibits that 24.6%(20.1GHz—26GHz) bandwidth and 22.9%(22.3GHz — 27.8GHz) 3d B axial ratio bandwidth are achieved respectively. The array has good properties of broadband and circular polarization based on the simulation results.Secondly, a 1 to 4 power divider for suspended strip line is designed. The power divider has an advantage of simple structure. All the transmission lines used in the divider have the equal width. The main structure that couples between the lines is realized by a T-shaped strip that is printed on the other side of the SSL dielectric substrate. A 4-unit circularly polarized slot antenna array is composed of the power divider and the slot antenna unit. The proposed antenna array exhibits that 25%(20.1GHz—26.1GHz) bandwidth and 12.5%(23.7GHz—26.7GHz) 3d B axial ratio bandwidth are achieved respectively. The results show that the antenna array realizes characteristics of broadband circular polarization.Finally, a metasurface(MS) antenna is designed. The MS consists of 16 unit cells arranged in a 4′4 layout. The MS can convert the linearly polarized(LP) signal from the slot antenna into a circularly polarized(CP) signal and can also increase the gain. The MS antenna exhibits that 22.5%(20.7GHz—26.0GHz) bandwidth and 8.9%(22.7GHz—24.8GHz) 3d B axial ratio bandwidth are achieved respectively. The MS antenna has good properties of broadband and circular polarization based on the simulation results.