طراحي و ساخت عدسي روتمن باند X با استفاده از سطوح سخت

چكيده انگليسي :

Design and Implementation of X band Rotman Lens Using Hard Surfaces Saeed Mahmoodi saeed mahmoodi@ec iut ac ir July 3 2019 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Assist Prof Zaker Hossein Firouzeh zhfirouzeh@cc iut ac ir Abstract Surface wave SW excitation is typically regarded as one of undesirable mechanisms in antenna design Techniquesare available to estimate the SW contribution on unwanted coupling between antenna elements diffraction from the edgesof the substrate and scan blindness in phased arrays Trade off between the efficiency and bandwidth in some applicationsforces designers to use thicker substrate to increase bandwidth However in some applications the main goal is to takeadvantages of SW with least possible leakage or radiated power For example bound SW power can be efficiently coupledinto the T M 0 SW mode of a grounded dielectric slab GDS as a feeding mechanism in leaky wave antennas This conceptis recently examined in SW based devise such as SW lenses SW power combiners and SW fed antennas In previousworks the SW excitation problem on a GDS by means of slots in the ground plane is considered as a two dimensional 2D model to extract closed forms for the power launched as SWs power leaked as radiation and input admittance of a slotsource Design of surface wave launchers SWLs in 2D model is based on choosing optimum slab thickness to maximizethe surface wave power excitation and to optimize impedance matching simultaneously In this framework However 2Dmodel only considers first moment of excitation and gives no vision or guarantee in terms of SW power confinement andSW power transmission Theoretical considerations in this thesis reveals that regardless of source position and polarization analyzing artificial impedance surface intrinsic properties such as reflection phase and surface impedance are sufficient toidentify the optimum excitation and power transmission in a SW waveguide SWG A systematic design strategy is pre sented which describes the implementation of SWGs using SWLs This design strategy is based on a hard surface conceptthat simultaneously guarantees mode purity launching efficiency SW power confinement and preventing backward SWpropagation In compare with full wave evaluating SW excitation performance of a slot antenna near the GDS this ap proach is computationally more efficient In addition to confirming the 2D model s precise results the proposed techniquepaves the physical interpretations and the way for the optimum design of SWGs By interpretation of intrinsic properties ofGDS we show that due to improper boundary conditions of GDS optimum SW confinement is not possible We modifythe boundary conditions to hard surface and demonstrate a SWG based on bow tie type self complementary metasurface Main idea in the proposed approach is that a SWL is intrinsically an antenna Generally the hard surface provides maxi mum mutual coupling between arbitrarily polarized antennas located on the same ground plane So for maximum powertransmission between two SWLs ground plane must be hard surface Also challenge in pure mode excitation comes fromthe fact that cross polarization of SWL is not zero and in practice the excitation of pure mode is impossible For a specificT M 0 SWL one can see that although TE radiation excitation due to a slot antenna in main beam is negligible but depend ofnatural properties of SWL in some angles even it could be dominant Hard surface by definition against TE waves acts likea high impedance surface so there is no possibility for excitation and propagation of TE waves The third challenge is thetransverse and longitudinal components of non TEM TE and TM modes in the slab which have sinusoidal characteristics This dependency in the third dimension questions the validity of traditional 2D models such as Rotman lens equations forSW based lenses In hard waveguides due to the redu

محمودي، سعيد

طراحي و ساخت عدسي روتمن باند X با استفاده از سطوح سخت

سطوح امپدانس مصنوعي , امواج سطحي , عدسي روتمن , فاز انعكاسي , سطوح سخت , پرتاب كننده موج سطحي