Principle And Design Of Planar Microwave Lens Based On MEFSS

Electromagnetic wavefront controlling is an important topic in the research of electromagnetic fields.The most classic way to achieve electromagnetic beam steering is phased array which use independently controlled periodic transmitting/receiving units.The emitter units in phased array can bend the beam by modulating its amplitude and phase according to the control system.However,the complex feeding network of numerous emitter elements increases its design difficulty and manufacturing cost.For traditional dielectric lens,it is realized by adjusting the thickness of homogeneous materials according to the wavefront carefully.However,the size and refractive factor of dielectric is sensitive to wavelength which will significantly reduce the performance if frequency shifts.The artificial electromagnetic surface provides an alternative solution for replacing bulky dielectric lens by building a simple planar microwave lens.Based on the research of miniaturized element frequency selective surface(MEFSS),we investigated a planar microwave lens operating in the X-band.In this thesis,we first elaborate on the construct of MEFSS.Due to its multilayer structure,equivalent circuit is an ideal analysis model to transform physical dimensions to analog circuit elements and we designed MEFSS with different orders to evaluate its performance.The S-parameter clearly show the pass band width and insertion loss by the order variation of MEFSS.Secondly,we explained several guidelines to construct the planar lens.Based on the generalized refraction theorem,we derive the relationship between phase distribution and lens factors which is determined by MEFSS.What's more,due to the similarity of planer units,the modeling of microwave lens could be accomplished by linking CST and Matlab in which the three-dimensional modeling and full-wave simulation could be automatically performed by m file.When CST full-wave simulation finished,we export the field data and proceed a detailed analysis of the performance.Getting inspired from array antenna,we rebuild the near field focusing model and recalculate the field distribution.The chosen one was optimized by comparing the theoretically calculation and full-wave simulation and the final results show its consistency with simulation.As for the case of oblique incidence,we use the model discussed above to calculate the field with the variation of incident angle and the factors that may affect the performance under oblique incidence are analyzed by taking the simulation as a reference.At the end of this thesis,the possible application of our proposed planar microwave lens is briefly described,which highlights its promising prospects in beam scanning antennas,multi-beam antennas and high-resolution imaging lenses.