| With the gradual improvement of 5G technology in recent years,people have become increasingly reliant on the convenience brought by wireless communication technology,while also placing higher demands on the regulation of electromagnetic waves.Reconfigurable metasurfaces,due to their advantages such as increased coverage range and signal intensity,reduced communication power consumption and cost,improved system capacity and performance,enhanced security and privacy protection,and support for multi-scene applications,will play an important role in the construction and application of future communication systems.Transmissive metasurfaces,with highly controllable,wide-band control capability,high transmittance and low loss,reconfigurability,and ultra-thin and lightweight characteristics,have broad application prospects in electromagnetic wave control and regulation.This thesis starts with an analysis of the unit characteristics of dynamic reconfigurable metasurfaces and studies the equivalent parameters of PIN diodes.Finally,a 1-bit reconfigurable transmissive metasurface based on PIN diodes is designed.Based on the PB phase principle,a symmetrical adjustable resonant current distribution is constructed using two reverse-biased diodes to achieve efficient phase control with equal phase shift across the entire frequency range.The main contributions of this thesis are as follows:The static and dynamic units were simulated using the waveguide emulator method and the Floquet port method,respectively.In the simulation of the dynamic unit,in order to conveniently feed the PIN diode loaded on the top metal layer in the waveguide test structure,the feeding line was buried in the intermediate dielectric layer,and the connection between the feeding line and the top metal layer was achieved through metallized through-holes.The amplitude and phase characteristics of the units were analyzed under these two electromagnetic simulation methods,verifying the equivalence between a specific incident angle in the waveguide mode and the Floquet port.For the static unit,the resonant point was around 100 GHz,and according to Equation 2-1,the incident angle corresponding to the WR10 waveguide at this frequency point was calculated to be 36°.By setting the incident angle to 36° at the Floquet port,the amplitude and phase characteristics of the unit in the waveguide could be effectively simulated.For the dynamic unit with the PIN diode,the incident angle was calculated to be 35° when the diode was conducting.For the dynamic unit with the Schottky diode,the incident angle was calculated to be 36° when the diode was conducting.The simulation results at the Floquet port and in the waveguide emulator were nearly identical.The experimental verification confirmed that the test results of the static unit and the dynamic unit with the loaded PIN diode in the waveguide emulator exhibited consistent trends with the results obtained from actual waveguide testing.A 1-bit reconfigurable transmissive metasurface has been designed,which can achieve perfect 180° phase shift with phase shift not varying with operating frequency.This is accomplished by controlling the voltage applied to two PIN diodes loaded on a metallic patch to operate in different states,thereby producing a reverse current.The symmetrical structure of the metasurface unit ensures that the transmission coefficients for the two states are exactly equal in magnitude.At 99.6 GHz,the transmittance coefficient S21 reaches its maximum value of-3.04 d B.The transmissive metasurface array enables flexible continuous control of dual beams in the angular ranges of-58.4°～-6.7° and 6.7°～58.4° in the millimeter wave band,achieved through the use of fractional coding and convolution coding for multiple beam reconstruction. |
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