Design Of Wideband Low Profile Antennas Based On Novel AMCs

With the development of mobile communication,Internet of Things and aerospace industries,higher requirements are placed on the miniaturization design of antennas because of the increasing integration degree of wireless systems.Due to the limited space of wireless devices,antennas are often required to have low profile features.With the development of antenna design theory,loading electromagnetic metasurface has been an important method for antenna designs.Artificial magnetic conductor(AMC)has high impedance and in-phase reflection characteristics,it can reduce the profile of the antenna compared with using the metal plate as the reflector.Therefore,this thesis takes AMC-based broadband low profile antennas as the research object.It aims to widen the AMC in-phase reflection bandwidth and reduce the antenna profile.The main contents of the thesis could be summarized as follows:1.A novel slotted circular patch AMC surface and a new double-ring AMC surface are proposed.The unit of the slotted circular patch AMC surface is based on a circular patch which is slotted to control the coupling characteristics of the equivalent LC.Therefore,high impedance performance and broadband in-phase reflection characteristics are obtained.After that,the effects of each parameter are analyzed.The simulation results show that the[-90°,+90°]in-phase reflection bandwidth of the slotted circular patch AMC structure is 5.68-8.52 GHz(40%).The double-ring AMC surface unit consists of two metal rings and four radial metal strips.After parameter analysis,high impedance characteristics and wideband in-phase reflection characteristics are obtained.The simulation results show that the[-90°,+90°]in-phase reflection bandwidth of the double-ring AMC surface is 4.64-7.05 GHz(41.23%).2.A low profile broadband linearly polarized antenna based on slotted circular patch AMC is designed.It consists of an elliptical slot antenna and an AMC reflector.The antenna is fed by a CPW structure.The upper elliptical slot antenna generates bidirectional radiation linearly polarized waves,and the lower AMC reflector superimposes the reflected wave and the forward wave in phase,thereby obtaining unidirectional radiation performance.Utilizing the in-phase reflection performance of AMC,the spatial phase delay caused by the air layer between the upper antenna and the lower AMC reflector is reduced,thereby reducing the profile of the antenna.The measured and simulated results show that the antenna has an impedance bandwidth of 5.06-7.92 GHz(44.07%)and a height of 0.101 ?L.3.A low profile broadband circularly polarized antenna based on double-ring AMC is proposed.It consists of a circularly polarized slot antenna fed by CPW,and a double-ring AMC reflector.The upper slot antenna generates bidirectionally radiated circularly polarized waves,and the lower AMC reflector reflects the electromagnetic waves to obtain unidirectional radiation performance.The AMC reflector has in-phase reflection characteristics which can reduce the antenna profile.The measured and simulated results show that the antenna has an impedance bandwidth of 2.07-5.21 GHz(86.26%),a 3 dB axial ratio bandwidth of 3.48-5.54 GHz(45.68%)and a height of 0.159 ?L.