The Study Of Near-field Exposure System Based On Millimeter-wave Planar Antenna

In this thesis,three kinds of near field exposure systems operating at 60GHz millimeter wave is designed,the model was optimized and improved,resulting in better uniformity of exposure systems.In order to study the bioelectromagnetic effect more efficiently,the near-field exposure system based on the substrate integrated waveguide is designed for large quantities of repeated experiments and less affected by the surrounding electromagnetic environment as a starting point.Based on the analysis of the substrate integrated waveguide basic theory,the appropriate waveguide size is selected,the simulation is carried out on the XFdtd electromagnetic simulation software.The grid size is set by using the sub-grid technology,and the mesh is optimized again by using the conformal algorithm.Finally,the specific absorption rate?SAR?mean value of the irradiation area was 1.56?10^-4 W/kg,and the relative standard deviation?RSD?was 74.5%.Then,a near-field exposure system based on choke ring antenna was designed.On the basis of the far-field irradiation system of choke ring,the multi-stage choke ring of closed structure is proposed,which is applied to near field irradiation.A detailed simulation analysis of the irradiation distance between the single stage and the multi-stage choke ring antenna is carried out.It is concluded that the exposure system based on the multi-stage choke antenna structure has more advantages in the near field exposure,the mean value of SAR was 1.61 W/kg,and the RSD was reduced to 44.1%.Finally,the near-field exposure system based on radial waveguide is designed.It is the first time that radial waveguide was proposed to apply to the near-field exposure system,and its bottom model is optimized.The feeder length of the system and the metal loading unit On the SAR distribution in exposure area is analyzed in turn.The results show that the SAR size distribution of the monolayer of culture medium varies with the fluctuation of the radius,especially in the central region,and the whole distribution present ring-shaped.For the first time,the copper cladding at the bottom of PCB is applied to improve the exposure area SAR value uniformity,through the bottom of the PCB board covered with circular metal,analysis of its impact on the SAR value distribution,and then adjust the shape of the coating,layers of progressive optimization,until the best results,the entire optimization process turns out to be clear and effective,the SAR mean value results were 1.90 W/kg and the RSD was reduced to 18.7%.