Investigations On Meta-surface For Beam Controlling

The beam controlling metasurface reconfigures the wireless propagation environment through programmable controlled reflections,which helps reduce the complexity,power consumption and hardware cost of large-scale multiple input multiple output(MIMO)systems.The beam controlling metasurface has high flexibility and is compatible with wireless communication systems,which will have broad application in the upcoming 5G era.According to the electromagnetic field theory,if each unit of the metasurface introduces the suitable phase compensation,the propagation direction of the reflected wave can be controlled.Based on this,1-bit controlled single beam metasurfaces in the 5GHz and39 GHz are designed and processed for verifing.The main work and innovations of this thesis are as follows:(1)An 1-bit unit is designed,and the reflection phase difference between ON and OFF is180°.In order to achieve single-beam controlling,90° pre-phase is introduced to form 4phase states.On the basis of single-layer dielectric unit,the thesis proposes unit loaded with air layer,unit loaded with PIN diode and uses the equivalent circuit of PIN diode for simulation.In order to introduce the 90° pre-phase,two method,stacking and loading delay line,are applied in the thesis.Finally,four kinds of unit structures,single-layer dielectric,loading air layer,loading PIN diode and loading delay line,are obtained,and their advantages and disadvantages are compared and analyzed.(2)Metasurface arrays with single beam pointing to-15°?15°?30° and 45° are designed respectively,for incident plane wave.The metasurface achieves single beam deflection with accurate beam direction and low sidelobe level,when a plane wave arrives perpendicularly.A 39 GHz metasurface loaded with delay line is processed and measured.The measurement results verify the feasibility and correctness of the 1-bit programmable single beam control of the metasurface.(3)The adjacent frequency performance and oblique incidence performance of the single beam metasurface are analyzed.In order to avoid adjacent frequency interference,the thesis proposes two filtering schemes: loading frequency selective surface(FSS)and loading filter elements.In the loading FSS scheme,a second-order band-pass FSS is designed.By placing it on the upper of the metasurface,the bandwidth of the entire system is narrowed and adjacent frequency performance and oblique incidence performance are improved;In the loading filter element scheme,a multi-layer slot coupling unit is designed,which can achieve filtering and programmable controlling by loading bandpass filters and switching elements.