Investigations Of Cloak And Antenna Technology Based On Metasurfaces

Metamaterials that are composed of sub-wavelength unit cells,have attracted a lot of attention from the researchers and have been rapidly developed due to their novel electromagnetic properties.Artificial electromagnetic surface,also termed as "metasurface",is a kind of two-dimensional special metamaterials.Metasurfaces have become a hot topic in the field of electromagnetics and optics in recent years because of their light weight and easy fabrication.In this thesis,functional devices are designed and realized by using metasurface,including carpet cloak,planar illusion device and radome with switchable function.The main contributions are as follows:1.We propose and design a multi-angles carpet cloak and a planar illusion device by using metasurface and the principle of phase compensation.In previous work,the carpet cloak based on the metasurface can act on the electromagnetic wave at only one single incident angle.In this thesis,active metasurface is introduced to design a multi-angle carpet cloak.The results of numerical simulation show that the carpet cloak can hide the target from the electromagnetic wave at several angles,finally,the realization method of the carpet cloak is discussed.In previous work,the electromagnetic illusion device based on the equivalent medium theory can work in two dimensions,and a certain polarization and narrow band of electromagnetic wave.In order to overcome these shortcomings,we use the metasurface to design the planar illusion device,which is very light and thin.2.The microwave-band radome with switchable function is designed,fabricated and tested by using transmissive metasurface.The active metasurface is introduced to design the wave-transmission sheet,and the transmission and reflection of electromagnetic wave can be switched.In the specific design,we realize the switches of high transmission(low insertion loss)and high reflection(high isolation)by using PIN diode and high frequency constant capacitor series instead of only the PIN diode.3.A reflective antenna based on the metasurface is designed.In the specific design,in order to reduce the blocking effect of the feedback antenna on the reflectarray,a planar antenna is designed as feeding,which has the characteristics of broadband,low profile and so on.In order to improve the coverage of reflection phases,a bilayer unit cell is designed.In the whole structure arrangement,the performance of the antenna is optimized based on the numerical simulation.The gain of the antenna is improved and the bandwidth is extended.