Transmission line interconnect

The North American electric power transmission system has been described as the largest, most complex machine ever built by humanity. It is a massive network of generating stations, transmission lines, substations, distribution lines, motors, and other electrical loads all interdependently linked for the conversion, transportation, and control of electrical energy. Approximately 60 percent of all energy utilized in the United States passes through the interconnected electric power system. The major goal of the system is to most efficiently and reliably deliver electric power from generating stations to residential, commercial, and industrial consumers. 

For digital circuits, the electrical length of the line can be defined relative to the signal rise time. A common rule of thumb for simple lines with no branches is that interconnections must be treated as transmission lines when the round-trip transit time of the signal, 2t pdZ, exceeds the signal rise time, tr (37). This rule defines a critical line length (Zc) given by... 

In other words, transmission lines are needed when the interconnection length is greater than one-fourth of the wavelength of the highest frequency harmonic. 

Transmission Line Structures and Characteristics. When interconnections exceed the critical line length, transmission lines with proper terminations are used to effectively couple the signal into the line, to minimize reflections along the line and from its ends, and to minimize crosstalk with adjacent lines. Transmission line structures provide a controlled environment... 

Modeling of High-Speed Interconnections. Modeling the electrical behavior of an interconnection involves two steps. First, the transmission line characteristics, such as the characteristic impedance, propagation constant, capacitance, resistance, dielectric conductance, and coupling parameters, must be calculated from the physical dimensions and material properties of the interconnection. In addition, structures, such as wire bonds, vias, and pins, must be represented by lumped resistance (R), inductance (L), and capacitance (C) elements. 

Transmission System (Electric) An interconnected group of electric transmission lines and associated equipment for moving or transferring electric energy in bulk between points of supply and points at which it is transformed for delivery to consumers or delivered to other electric systems. 

An important application for garnets is for isolators in optical communications systems. Reflections from end-faces of components and interconnections in an optical transmission line have a destabilizing effect on the operation of the laser sources and have to be eliminated. This is achieved using an optical isolator , the optical analogue (2 typically in the range 1.30—1.55 /mi) of the microwave isolator described in Section 9.5.5. 

A major degradation mechanism of modules is the decrease in fill factor. This is caused by an increase in the diode quality factor of the cells making up the module and by an increase in series resistance. The former is related more to the absorber and heterojunction properties and less to the ZnO properties. The series resistance increases because the conductivity of the ZnO drops and because the interconnects are deteriorating. Wennerberg et al. have assessed the individual contributions to increased series resistance [50]. Klaer et al. [52,53] have described a transmission-line test structure that allows to separate the contributions of contact and sheet resistance, respectively. The test structure is prepared by the same scribing techniques as those used in module manufacturing. 

The foundation for such a market is the high voltage electric transmission grid. The interconnected electric transmission grid in North America is one of the largest and most complex man-made objects ever created. This grid, which encompasses the entire North American continent, consists of four large 60-Hz ac synchronous subsystems. These subsystems are 1) the Eastern Interconnect, which supplies electric power to most users east of the Rocky Mountains 2) the Western Interconnect, which supplies power to most users west of the Rockies and portions of Northern Mexico 3) the Texas Interconnect, which supplies most of Texas and 4) the Quebec Interconnect. These four subsystems are in turn connected to each other by dc transmission lines and back-to-back convert-... 

In the lower 48 states, there are about 300,000 kilometers of interconnected transmission lines, operated by about 500 different companies. 

The simplest microwave circuit element is a uniform section of transmission line which can be used to introduce a time delay or a frequency-dependent phase shift. Other Hne segments for interconnections include bends, corners, twists, and transitions between lines of different dimensions. (See Fig. 4.22.) The dimensions and shapes are designed to minimize reflections and so maximize return loss and minimize insertion loss. 

FIGURE 4.22 Sections of transmission lines used for interconnecting components (a) waveguide tapered section,... 

For a lossy transmission fine due to parasitic resistance of on-chip interconnects, an exponential attenuating transfer function can be applied to the signal transfer at any point on the transmission line. The rate of the attenuation is proportional to the unit resistance of the interconnect. When operating frequency increases beyond a certain level, the on-chip transmission media exhibits the skin effect in which the time-varying currents concentrate near the skin of the conductor. Therefore, the unit resistance of the transmission media increases dramatically. 

For information on modeling of VLSI interconnects and their transmission line treatment, consult the Proceedings of Design Automation Conference and International Conference on Computer-Aided Design. IEEE Transactions on CAD is also an excellent source of information on the subject. 

Unlike notch systems, in a bandpass system the accum ulate d p ower entering each module flows only through the output hybrid, so the power-handling capacity of the system is Hmited only by the size of the output hybrids and interconnecting transmission line, not the entire module. 

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