Research On Left-Hnaded Microstrip Waveguiding Structure And Its Applications

In recent years, a kind of "left-handed materials"(LHMs), the artificial equivalent materials in solid-state physics, materials science, optical and electromagnetic fields starts to obtain the increasingly widespread favor, and the research is showing its rapid development. But its appearance was acturally from the former Soviet Union scientists V. G. Vesalago imagination in the 1960s.In physics, the permittivityεand the permeabilityμare the two fundamental physical quantities, which describe the electromagnetism nature of the material. In the known material world, to the electromagnetic medium, the permittivityεand the permeabilityμare both positive, where the electric field, the magnetic filed and the wave vector satisfy the right hand relations, and such materials are called right-handed materials (RHMs). Since this kind of right-hand rule was considered necessarily the natural convention, but this convention had been suffering the subversive challenge from the 1960s. In 1967, the former Soviet Union physicist V. G. Vesalago published a paper in a former Soviet Union academic publication, and had reported for the first time in novel discovery relating to the fundamental research of the material electromagnetic nature. Namely, the electric field, the magnetic filed and the wave vector satisfy the left hand relations when the permittivityεand the permeabilityμare simultaneity negative. He called this kind of imaginary material the left-handed material (LHM), and predicted that the electromagnetic behavior in LHM was opposite to that in the RHM. For instances, the reversed Doppler Effect, the reversed Snell Refraction and the reversed Cerenkov Radiation, etc. This paper aroused an English man's interest, and was translated into English for publishing in another former Soviet Union physics academic publication in 1968. However, hardly anybody at that time realized that the material world henceforth opens the new page.Because there is no left-handed materials existence in the nature world, the research on the LHMs is not plain sailing. Although it has so many strange natures, all the research is limited to theoretical analysis. The supposition had not been accepted by the people until the end of the last century, when the first light of morning appeared. In 1996, John Pendry and his group in the Blackett Lab. of United Kingdom pointed out that the negative permittivityεmedium can be constructed from the thin copper wires structure. And in 1999, they demonstrated that the negative permeabilityμmedium can be constructed from the structure of split-ring resonators.In 2001, David Smith and his group at University of California, San Diego, published the paper on the Science magazine, in which the artificial material with the permittivityεand the permeabilityμsimultaneity negative was constructed by John Pendry.By the end of 2002, Professor Jin Au Kong from MIT proved the rationality of the existence of LHM, and pointed out that this kind of artificial material are highly promising in high- directional antennas making, microwave beam focused to achieve "perfect lens", the electromagnetic stealth and so on. The prospect of LHM starts to arouse the infinite dreams of the academia, the industrial field and particular the military.2003 was the golden year for LHM researching in which many breakthroughs were obtained. The group at Boeing Phantom Works and another group at University of Toronto demonstrated the concept of a negative refraction in the labs. And S. Foteinopoulo at Iowa State University also published the simulated results of the LHMs that constructed with photonic crystal. Based on these discoveries, the development of LHMs impressively entered the world's top ten scientific advances selected by the Science Magazine in 2003, and attracted global attention.Because the LHMs are composed of the thin copper wires and split-ring resonators, which have large insert-loss and narrow left-handed frequency band, and so on, it is very difficultly to be applied in microwave and millimeter wave system. In the begin of 2003, Professor Arthur A. Olinear, T. Itol and George V. Eleftheriades realized that a transmission line approach towards LHMs was possible, which had been demonstrated by having low loss and wide left-haned frequency band, and provided the possibility for LHMs in the microwave and millimeter wave system applications.With the remarkable characteristic of LHMs of simultaneously negative permittivityε and permeabilityμ, the LHM is also called Double Negative Material (DNM), or Material with Negative Refractive Index (MNR).The concept of LHM and the study course in the international electromagnetism are briefly introduced at the beginning of the thesis. Then, based on the model of left-handed transmission lines (LH-TLs), a novel left-handed microstrip unit structure is presented, which has smaller size and lower insert-loss. At the same time, the extraction process of the model parameters in the unit structure is given, which provides the foundation in microwave and millimeter wave system applications. The experiment confirmes the equivalent realization of LH-TLsThen, the 1-dimension LH-TLs applications researches in microwave and millimeter wave system are analyzed. At first, the TLs approach of LH materials is based on the dual of the conventional transmission lines. Because of unavoidable parasitic series inductance and shunt capacitance resulting in a RH contribution increasing with frequency, the LH transmission line is a composite right-left handed transmission line (CRLH-TL). We obtain an ultra-wide band (UWB) filter network through the appropriate choice parameters. Second, based on the advance phase shift characteristics of LHMs, a novel balun structure with CRLH-TL is presented. Combined the traditional right-handed line with CRLH-TL, the process of design balun will become more easy and simple. At last, a novel feeding network for 2-dimension millimeter wave microstrip patch arrays with CRLH-TL is proposed. Because of the simpler structure and the shorter length of the CRLH-TL feeding network, the antenna array is of higher gain than that with the conventional parallel feed network. Besides, the radiation pattern shift resulting from the traditional parallel-series feeding network is removed since no inserting phases shift are introduced in the patch elements using the novel feeding structure.Synchronously, a novel unit of planar distributed structure with double negative material (DNM) is proposed. The present unit cell implemented with microstrip structure has composite structure on single-layer but not two layers as did before. By using interdigital capacitor instead of the former mushroom structure with caps, the structure has depressed the left-handed transmission frequency band than the former one. And the extraction process of the model parameters in the unit structure is also given. Also, a new DNM lens based on the present planar distributed 2-D structure, which id interfaced with two parallel-plate waveguides (PPWs) is designed and simulated. The focusing/refocusing effect is observed by full-wave simulations.The investigation in this thesis is of theoretically and practically significant for realization the microstrip unit structure of the LH-TLs, and for novel applications in the microwave and millimeter wave system. Furthermore, this work is valuable for design of components in the microstrip circuits and microwave system based on the left-handed materials.