Electrical characterization and performance limits of a flexible cable

Abstract

The electrical performance of a flexible-cable test structure is characterized from low frequencies up to 2i GHz. The experimental results are used to develop and refine models which describe the performance of such cables, with particular emphasis on the contribution of dielectric and resistive losses, including slcln effect. The capability of triplate flexible cables to provide high-bandwidth connections over long lengths is investigated with the models developed. A triplate design Is chosen because it offers high density, limited crosstalk, no loss through radiation, and relatively inexpensive fabrication. Bit rates of 100 Mb/s-1 Gb/s are considered for propagation over lengths up to 250 cm. The paper highlights the performance-limiting factors through realistic examples. Including the contribution of interfaces to other interconnection structures.

Performance limits of electrical cables for intrasystem communication

“…While thick layers can be laminated together, small vias cannot be fabricated in the resulting structure, and its stiffness becomes unmanageable. As discussed in [9], conductor cross sections larger than 0.203 x 0.035 mm (8 x 1.4 mils) are not considered feasible, thus limiting useful lengths of flexible-film cables to less than 2.5 m. In a specific system application, many factors must be considered in order to determine the maximum useful lengths of different cable options. These include the physical location of the driver and receiver circuits; noise budgets; the losses in the printed-circuit-board signal lines; the impedance mismatches between the cards, cables, connectors, and terminating resistors; the inductive and capacitive discontinuities due to the connectors and vias; crosstalk; and the tolerances of all these components.…”

“…The length reduces to 3.0 m for 1-Gb/s transmission. In this case, the rise-time dispersion reduces the steadystate level because of rounding of the upper and lower parts of the rise and fall times of the pulses, as is explained in [9]. Skin-effect and dielectric losses in the card traces and distortions caused by the reflections from connectors and vias further slow down the rise time and reduce the expected useful lengths to 3.5 and 1.…”

Electrical characteristics of interconnections for high-performance systems

“…While thick layers can be laminated together, small vias cannot be fabricated in the resulting structure, and its stiffness becomes unmanageable. As discussed in [36], conductor cross sections larger than 0.203 0.035 mm (8 1.4 mil) are not considered feasible, thus limiting useful lengths of flexible-film cables to less than 2.5 m. Most of the coaxial and ribbon cables cost about 50 cents per foot. Most of the cost of all the cables is in the assembly of the end connectors.…”