The Research Of Let-Handed Waveguide

Artifical electromagnetic materials with effective negative permittivity and permeability have attracted microwave community in recent years. These structures, which exhibit extraordinary properties not generally found in nature, are referred to as left-handed metamaterials (LHMs). Scientists predict LHMs can find important applications in areas such as information and military technology. One-demensional LHMs are also called left-handed trainsmission lines (LHTLs). Because of their simple structures, LHTLs are most likely to be the most widely used form of LHMs. At present, the researchers mainly focus on planar circuit (microstrip, coplanar waveguide, etc) based LHTLs and pay a little attention to waveguide based LHTLs namely left-handed (LH) waveguides. Because of basing on waveguides, LH waveguides are suitable to be used in high-power and low-loss apllications. Therefore, the research of LH waveguides is a very potential area, which has a large practical value.This thesis mainly focuses on the realization, application and EM modeling/simulation of LH waveguides.In the third chapter, according the transmission line theory of LHM, based on the coaxial waveguide, coaxial LH waveguide is proposed. This new LH waveguide is analyzed by means of circuit theory. The unit propagation constant, Bloch impendence, effective permittivity, effective permeability, effective index of refraction and other relevant parameters are obtained. Both theory analysis and EM simulation show that the proposed structure exhibits LH behavior.In the forth chapter, based on resonant-slot coupled cavity, resonant-slot coupled cavity chain LH waveguide is proposed, which is a novel kind of LH waveguide. The proposed LH waveguide is analyzed by means of field theory and its unit dispersion equation is obtained. By theory analysis and EM simulation, a LH passband is proved to be existed. The new structure overcomes drawbacks of previous approaches with wide LH passband, low loss and high power capability.In the fifth chapter, according to the theory of LHM based subwavelength cavity resonator, LH/RH waveguide subwavelength cavity resonator is proposed. This new resonator is based on RH waveguide (namely coaxial waveguide) and LH waveguide. Simulation and experimental results prove that the lengths of these cavity resonators can be much shorter than that of the conventional half-wavelength cavity resonator while working at the same frequency. As compared to former subwavelength cavity resonators based on the same theory, the new cavity resonator is more simple, more stable and easier to be fabricated. Due to the closed all-metal and non-substrate construction, the new cavity resonator can be operated in a high power condition and obtain a low loss.In the sixth chapter, a novel resonant slotted-waveguide array based on the infinite wavelength propagation property of practical LH waveguide is presented. The slot elements on the LH waveguide wall are unequally spaced to tailor the radiation pattern. To ensure that excitations of all unequally spaced slot elements are in-phase to generate a broadside beam, LH waveguide should work at the infinite wavelength propagation frequency. Because of extra control variables, better radiation pattern performances can be obtained in comparison with the conventional resonant slotted-waveguide array.In the seventh chapter, by employing simplified resonant-slot coupled cavity chain LH waveguide and introducing element amplitude into the array synthesis, the LH waveguide based unequally spaced resonant slotted-waveguide arrays with better perfence and more close to practical application are proposed. Through array synthesis, simulation and experiment of four arrys with different radation patterns, it is proved that proposed unequally spaced resonant slotted-waveguide arrays are reasonable.In the eighth chapter, two LH waveguide unit modeling and corresponding LH waveguide structure simulation methods are proposed. The two methods can be used for fast EM simulation of LH waveguide structure. The first method is realized by storing the so-called compressed stiffness matrix and the other related matices of LH waveguide unit under given geometry parameters and frequency. This modeling method together with its corresponding EM simulation method is called direct modeling-EM simulation method. The second method is based on the first one, and it is realized by using neural network to learn the spatial EM-coupling relation between the interfaces of LH waveguide unit. This modeling method together with its corresponding EM simulation method is called neural network modeling-EM simulation method. By utilizing the presented mesh change technique, the obtained LH waveguide unit models from the two methods can be used in different mesh in the simulation. Either of the two proposed methods has advantages and disadvantages. Simulation examples prove that the two proposed methods are faster than the standard fininte element method in the LH waveguide structure simulation.