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Synthesis of Parallel Wires

IP.com Disclosure Number: IPCOM000079184D
Original Publication Date: 1973-May-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

Ruehli, AE: AUTHOR [+3]

Abstract

The synthesis of transmission-line structures is an important subject for both time domain application (e.g. design of computer packages and chips), as well as for frequency domain applications. Examples for frequency domain applications are printed-circuit filters and the design of directional couplers.

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Synthesis of Parallel Wires

The synthesis of transmission-line structures is an important subject for both time domain application (e.g. design of computer packages and chips), as well as for frequency domain applications. Examples for frequency domain applications are printed-circuit filters and the design of directional couplers.

As a specific case for the synthesis the coefficient of capacitance matrix is considered. This is a basic problem in the applications given above. Specifically, in a computer package, wires are designed to have a given self and coupling capacitance. In an optimal design, the conductors are then spaced as closely as possible without exceeding the capacitance coupling that can be tolerated between them For directional couplers, a matrix of characteristic impedances Z(0)=1 over v c/-1/ must be realized, where v is the velocity of propagation and c is the coefficient of the capacitance matrix.

Even for the cases where couplings among conductors is insignificant, one very important area in strip transmission-lines synthesis is the impedance matching problem. In on or off logic or memory chips, signals propagate from device-to-device through strip lines. The amount of power that can be transmitted on the lines, depends directly upon the matching of the output impedance of the device to the characteristic impedance of the line. The method that is described herein can be applied as follows.

Given an impedance value Z(0) to be matched by the line, the parameters of the line viz. h, t and w shown in Fig. 1, are used such that the sensitivities of the characteristic impedance of the line, Z versus h, t and w are computed. Optimization algorithms are then used to minimize the difference between Z and Z(0). The sensitivities such as the dimensions h, t, and w can be used in a very flexible way to fit into any technology of interest, e.g., the strip line dimension can be scaled up or scaled down, or the parameters can be subjected to various minimum or maximum values constrained by the technologies. In every case, this method can either meet the required impedance Z or find the best approxi...