A Basic Research on Design Approach of Uniplanar Wave Guides for Millimeter-Wave Integrated Circuits and Leakage Effect on Their Wave Guides

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The Printed-circuit lines (or wave guides) considered in this research are microstrip line, slot line and coplanar wave guide. Slot line and coplanar wave guide, furthermore, have several variants. The conductors on these lines may be finite or infinite in lateral extent, and the lines may be conductor backed or simply rest on a dielectric substrate.Under appropriate conditions, all of these lines, in one way or another, will leak power above some critical frequency. We were the first to discover this new leakage effect, in which the power will radiate away in the lateral direction at an angle that will change as the frequency is varied, and with a leakage rate that is also frequency sensitive. Furthermore, it is the dominant mode on these lines that becomes leaky, contrary to general expectations.The manner in which the dominant mode becomes leaky, and the critical frequency at which this occurs, are different for each of the guiding structures. Nevertheless, the basic physical idea c … More ommon to all these cases is quite simple. In this research, we have explained it qualitatively and with numerical examples, providing experimental results that prove our theory.The present research also discusses a new mode-coupling effect. It has been appreciated that modes on printed-circuit wave guides can interact with the modes of the box or package in which they are placed, and that this interaction will produce mode-coupling effects. The significant difference in the present work is that the coupling effect occurs even though no box or package is introduced. This new coupling, which involves the dominant mode, has not been recognized before in the literature, nor has attention been paid to the newly identified mode that causes the coupling. As an example, we report such a mode-coupling effect that occurs on conventional coplanar wave guides of finite width.The electromagnetics involved in the new leakage effect and the modecoupling effect discovered in this research are very interesting in its own right, but the practical implications, in the form of cross talk and power loss in integrated circuits, and pulse distortion for ultrafast pluses, can be serious. Less