High-performance Interconnect Systems for Mobile Communications
By Paul Carter, Whitney Blake

Advances in technology touch every manner in which we conduct our daily lives and nothing has become more important than clear, concise communications. Just as technology has driven advances in wireless communications and the expansion of communications networks, the need for high-performance tethered product has expanded as well.

Modern battlefields are replete with electronics systems, radar signals, and equipment generating an enormous amount of EMI (electro-magnetic interference) which pose unique challenges for communications systems. Such hostile environments demand engineered products that provide a high-degree of shielding effectiveness while maintaining high flexibility and long service life under rugged environmental conditions. To execute their mission, today’s military personnel must have the best technology at hand.

The need for constant contact is not limited only to military applications. Life or death situations can hinge on quality communication with police, fire, and rescue personnel as well. Entertainment industry professionals also benefit from the use of handsets and headsets for security at concerts, sporting events, and other public assemblies. Specialty cables used in extreme environments, such as avionics and fire rescue, require additional consideration of flame retardants and survivability under catastrophic conditions.

Defining the Interconnect Challenge
Many of today’s headsets and handsets rely on advanced interconnectivity solutions–connections designed to ensure that cable products deliver the most reliable and consistent data and power transfer available. In robust environments where optimum performance is required, technology is the driver for product design. Today’s high-performance applications have specific requirements related to data rates, shielding, and flexibility requiring a broad scope of core competencies to meet these requirements.

As communications equipment have become lighter and more portable, a distinct need has developed for highly flexible cable, coiled cords, and custom over-molds. Specific design requirements must be achieved to yield a highly flexible, yet durable, product. Selections of conductor material, strand count, primary jacket compound, shielding, and overall jacket, each play a critical role in product performance. These materials must all work as a complete system, requiring that product design consider lay length and direction, jacket wall thickness, metal-to-plastic ratios, and a number of other considerations in order to optimize performance.

It is not just the material selection but the parameters used in manufacturing that impact results. The communications cable or coiled cord must be married to a connector system through the development of an appropriate over-mold using specific materials to enhance performance. To achieve the best results for your application, use discretion in choosing a supplier that has the expertise you need in cable design and manufacturing, cable assembly, and over-molding.

Interconnect Technology Drivers
Today’s technology-driven companies need cable systems–integration of cable, over-mold and assembly expertise–rather than mere cable assemblies. Of primary concern is the need to maintain a very high degree of shielding effectiveness while providing a supple cable usually in the form of a coiled cord that will allow the user free range-of-motion.

High-performance over-mold design is the linchpin between the cable and connector system. Design considerations include application mobility, operating temperature, mechanical requirements, and compound compatibility with jacket materials–all playing a key roll in the success of the overall system. Shielded assemblies require special consideration to ensure that the shield remains contiguous throughout the mold.

Over-molding can also provide environmental protection to the mated-pair through the designed introduction of an interfacial moisture sealing ring. The seal rings inhibit the migration of moisture into the connector system, moisture that can affect the signal integrity and enhance corrosion. Over-mold systems can also provide protection to the cable and equipment through development of systems that de-mate at designed pull-strength. If excessive force is put on the cable, it will simply disconnect, rather than incurring the damages that usually result from a positive mating system.

Staying Flexible: Performance vs. Cost
Performance versus cost consideration is a conundrum faced by all design engineers when considering product applications. Materials selection, driven by application requirements, plays a large part in driving cost.

A number of extrusion compounds can be used for insulation and jacket materials, each of which offers particular cost versus performance trade-offs. These materials are divided into two categories: thermoplastic and thermoset. Thermoplastics, such as PVC (polyvinyl chloride), polyurethane, and TPR (thermoplastic rubber) are resins that can be readily softened and reformed by heating and be rehardened by cooling. Thermoset materials, such as Neoprene and SBR (styrene butadiene), contain resin which cures by chemical reaction.

Within the thermoplastic group, the polyurethanes are most expensive. However, they offer better chemical and flame-resistance than PVCs, and tend to provide better retractile properties for coiled cords. The thermoset products are more expensive to purchase and process, but they offer outstanding chemical resistance. Additionally, when used in coiled cords, thermoset products exhibit more linear force to extend and they offer better retractile properties at elevated operating temperatures.

Interconnect solution providers are challenged to provide effective shielding and good noise reduction because they usually come with performance and cost trade-offs to the OEM. Shielding for retractile cords is performed using several different methods and materials, including the shielding of individual wires, twisted pairs or groups of wires, and/or the use of an overall shield. Common shielding materials include spiral served copper or copper alloy wires, laminated aluminum and copper tapes, braided copper or copper alloy wires, and semi-conductive thermoplastics.

Users of headsets and handsets count on clear, reliable communications to maintain situational awareness to accomplish their missions. Manufacturers of these devices benefit from the technical expertise of a fully-integrated, engineering-driven manufacturer of high-performance interconnect systems. This expertise will ensure that your mobile communications products are durable, lightweight, weather-resistant, and reliable in the most severe operating environments.