Research On Wideband Multi-band Multi-polarized Multi-radiation Pattern Stacked Microstrip Antenna

In recent years,with the innovation of modern communication technologies have promoted the development of antennas in the direction of high spectrum utilization,multi-function,transceiver integration.With the arrival of 5G commercials in 2020,more and more people will use wireless communications,the difference between existing spectrum resources and people's needs is gradually increasing,further requiring new antennas have better performance such as wideband,multi-band,multi-polarization,and multi-radiation pattern.In thesis paper,the antenna with the characteristics of ultra-wideband,circular polarization,dual-band,dual-polarization and diverse pattern are considered as research objects.Finally,two types of multi-feed stacked microstrip antennas with broadband baluns and a stacked microstrip antenna fed by coaxial cable are designed.The main work of thesis paper are as follow:In the first,the basic theory and performance index of microstrip antenna are introduced.Then,the principle of ultra-wideband,dual-band,circular polarization and dual-polarization of microstrip antennas are researched.Meanwhile,the specific approaches to obtain these characteristics are also depicted.A dual-feed ultra-wideband stacked antenna with circular polarization is researched and designed.The method of realizing circularly polarization characteristics is discussed intensively.Meanwhile,in order to solve the problem of narrow band and low gain,the radiating portion of the antenna is composed of a structure in which two substrates are stacked from top to bottom.A microstrip balun,consists of a 3 dB Wilkinson splitter and a 90° phase shifter,worked as the feeding part of the antenna to realize the circular polarization characteristic.Then,a 270°metal strips is introduced to improve the circular polarization purity of the antenna.At the same time,due to the large bandwidth of microstrip balun and the high gain of stacked substrate,a high gain stacked antenna with ultra-wideband and circular polarization characteristics is designed.A stacked-patch dual-band and dual-polarized antenna with broadband baluns is studied and fabricated.Further analysis and discussion on the dual-feed antenna with single polarization performance,an antenna with vertical polarization and horizontal polarization is designed by symmetrically adding a pair of coaxial feeding points.At the same time,the feature of dual-band is realized by placing two patches on the upper and lower substrates.The balun consisting of a 3 dB Wilkinson splitter and a 1800°phase shifter,and the balun can continuously output signals with equal amplitude and opposite phase which greatly improve the isolation and the ability of cross-polarization suppression.A dual-band microstrip antenna fed by coaxial cable with diverse radiation patterns is studied and fabricated.Two stacked patches are introduced in this antenna to obtain dual band characteristics.The surface current on the turnstile-shaped patch and circular parasitic patch constitute current loop which can be equivalent magnetic dipole.Then,an antenna with dual-band performance and omnidirectional radiation patterns is achieved.On the basis,the antenna structure is further optimized,an electric dipole is introduced by etching rectangular slot on the circular parasitic patch to change the current path.The combination of the magnetic dipole and the electric dipole achieves directional radiation.Finally,a dual-band microstrip antenna with nine radiation modes is obtained by the electrical modulation of the PIN diode in the rectangular slot.