| Coplanar waveguide(CPW) that which is originated from microstrip is an important planar transmission line of microwave. With the development of microwave and millimeter-wave integrated circuits, especially of monolithic microwave integrated circuits, there is a great interest in the coplanar waveguide in recent years. Coplanar waveguides(CPW's) offer several advantages over conventional microstrips, these include the simplification of the circuit fabrication process, ease of parallel and series insertion of both active and passive components (without the need for via holes), and high circuit density. Therefore CPW's are widely used in microwave and millimeter-wave integrated circuits, optical and High Temperature Superconductor Microwave devices.Although there are many researches about CPW's, the most of them are given only for symmetric CPW's, and moreover, there is few literatures published about the studies of field patterns of coplanar waveguides. Compared with symmetric CPW's, asymmetric lines facilitate the connection of devices on microwave circuits. Asymmetric CPW's are of generality, and the symmetric lines can be considered as the special cases of asymmetric lines. In fact, CPW's designed to be symmetrical are asymmetrical because of the imperfect of the fabrication. So the studies of asymmetric CPW's is actually important.The electric and magnetic field pattern of CPW's is helpful for us to understand how the lines operate, the field confinements and coupling effects of the lines, and the analysis of power loss. Thus the field patterns can help us to design devices especially design CPW directional couplers.In sum, it is of great value to both theories and applications for us to continually study CPW's, especially the characteristics and the field pattern of CPW's. Having consulted the study of domestic and foreign researcher on CPW's, this paper studies the characteristic parameters of many asymmetric CPW's, the calculation and the plotting for field patterns of CPW's.In order to apply the research results of this paper to the optimum design of computer for CPW, the analytical closed-from of expressions is the best choice. So conformal mapping theories are used to analyze CPW's by this paper. The optimum programming, the numerical inversion of conformal transformation and the numericalpredictor-corrector method have been utilized to calculate the characteristic parameters and field patterns of CPW's. It is true that the all formula from conformal mapping is valid only for TEM modes. Because the media in CPW's consists of air and another dielectric, the longitudinal components of E-H field exist in CPW's. However the magnitude of the longitudinal components is less than 1% of the transverse field, when the size of CPW's is very small. So we can approximately consider the field in CPW's as TEM wave.This paper not only has studied asymmetric CPW's, but also fabricated firstly an asymmetric CPW with conductor backing in china. Its relative dielectric constant is 9.9. The characteristic impedance of these asymmetric CPW's is measured.In the research on the characteristic and the field patterns of various asymmetric CPW's, many results are obtained by this paper. These results are as follows.1. The asymmetric CPW with conductor backing, the asymmetric CPW with wholly shielding and the asymmetric CPW with both finite substrate thickness and finite lateral ground planes are put forward, and the analyzing methods of these CPW's are presented. By the methods of conformal mapping, the closed-form analytical expressions for characteristic impedance per unit length and relative effective dielectric permittivity are deduced for the three asymmetric CPW's, and the analytical expressions of the electric field for asymmetric CPW with conductor backing is derived. The characteristic parameters of asymmetric CPW's which are related to the structure dimensions are evaluated, and the graphical results of parameters which vary depending on structure dimensions of asymmetric CPW's are offered.
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