Coaxial Cable and Method of Construction Thereof

Abstract

A coaxial cable and method of construction thereof are provided. The coaxial cable includes an elongate central conductive member; a dielectric insulative layer encasing the central conductive member; an outer protective sheath, and a braided EMI shield layer including hybrid yarn sandwiched between the dielectric insulative layer and the outer protective sheath. The hybrid yarn includes an elongate nonconductive filament and an elongate continuous conductive wire filament. The wire filament is interlaced in electrical communication with itself or other wire filaments along a length of the EMI shield layer to provide protection to the central conductive member against at least one of EMI, RFI or ESD. The method includes providing a central conductive member; forming a dielectric insulative layer surrounding the central conductive member; braiding an EMI shield layer including hybrid yarn about the insulative layer, and forming an outer protective sheath about the braided EMI shield layer.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit of U.S. Provisional Application Ser. No. 61 / 736,977, filed Dec. 13, 2012, which is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION[0002]1. Technical Field[0003]This invention relates generally to sleeves for protecting elongate electrical members and more particularly to coaxial cables having an electromagnetic interference shield layer sandwiched between an inner insulative layer and an outer sheath.[0004]2. Related Art[0005]It is known that electromagnetic interference (EMI), radio frequency interference (RFI), and electrostatic discharge (ESD) can present a potential problem to the proper functioning of electronic components due to signal interference caused by inductive coupling between nearby electrical conductors and propagating electromagnetic waves. Electronic systems generate electromagnetic energy as a result of current flow through a circuit. This electromagnetic e...

AI Technical Summary

Benefits of technology

The invention provides a coaxial cable with an elongated central conductor, a layer of insulation, and a braided layer to protect against EMI, RFI, and ESD. The braided layer includes a nonconductive filament and a continuous conductive wire filament. The cable also has a reduced mass and increased flexibility due to a thinner outer protective layer. The elastic push-back property of the braided layer is improved to prevent permanent gaps between the filaments.

Problems solved by technology

It is known that electromagnetic interference (EMI), radio frequency interference (RFI), and electrostatic discharge (ESD) can present a potential problem to the proper functioning of electronic components due to signal interference caused by inductive coupling between nearby electrical conductors and propagating electromagnetic waves.

This electromagnetic energy can adversely affect the performance of surrounding electronic components, whether they are in direct communication within the circuit or located nearby.

For example, electrical currents in conductors associated with an electrical power system in an automobile may induce spurious interference signals in various electronic components, such as an electronic module.

Such interference could downgrade the performance of the electronic module or other components in the vehicle, thereby causing the vehicle to function other than desired.

Similarly, inductive coupling, such as between electrical wiring in relatively close relation to lines carrying data in a computer network or other communication system, may have a corrupting effect on the data being transmitted over the network.

While coaxial cables are generally effective at forming a reliable electrical circuit and eliminating electrical interference, the known cables have inherent drawbacks.

Although this provides an effective barrier against EMI, it is expensive given the high content of the tin or copper metal wire.

In addition, with the EMI shield layer being constructed solely from metal, the stiffness is relatively high, and thus, the ability to route the coaxial cable over a meandering path and / or about a corner is jeopardized.

Further yet, with the EMI shield layer being made entirely of metal, it is aggressive in its ability to mechanically abrade the inner insulative layer and the relatively thick outermost protective sheath.

Accordingly, the stiffness and mass of the coaxial cable is increased, thereby further diminishing the flexibility of the cable and requiring an increased amount of space to route the cable due to its relative stiffness.

The need for an increased amount of space can be very costly and prohibitive where space is at a premium, and further, the increased stiffness can result in damage to the cable if the cable is bent beyond its flex capacity.

In addition to the aforementioned drawbacks, a further drawback results from having a pure metal EMI layer, namely, the inability of the pure metal EMI layer to dampen shock, which ultimately can result in damage to the functionality of the cable.

Yet a further drawback results from having a pure metal EMI layer, namely, a reduced ability of the pure metal EMI layer to elastically return to its originally braided configuration, typically referred to as ability to elastically “spring-back”, also referred to as “push-back”, upon being bent.

As such, a pure metal EMI layer, upon being bent is susceptible to permanent, plastic deformation, which can produce undesirable permanent gaps between adjacent braided metal wires.

Gaps of unintended, increased size between adjacent wires can ultimately reduce the EMI shielding effectiveness of the EMI layer, and thus, the functionality of the coaxial cable can be diminished.

Images