Select a cable for a high-speed application

With the increasing number of wireless applications in the world, the irony is that it is increasingly necessary to use wires and cables in high-speed environments. A senior system engineer named Carroll Wontrop from Danaher Motion in wooddell, Illinois, said: "wireless is a competitor, but in a habit, it may be difficult for users to perform conversions ".

People are worried that wireless communication will be vulnerable to interference from other wireless communications. Therefore, design engineers and system designers shoulder unprecedented pressure when choosing the right connection method.

So what factors should electrical engineers consider when specifying a connection method for high-speed data transmission applications? I once asked some industry professionals with various backgrounds about this question. We hope this introduction will make the selection process a little simpler.

Optical Cable and copper cable

Cable challenges have been around for a long time. Although optical fiber cables have clear performance advantages and are generally considered to replace the cables at some point in time, they still exist, this is largely due to the fact that its reliability, quality, and most of the existing infrastructure provide excellent compatibility with cables. Therefore, many designers do not know how to choose between them.

Emad Soubh, high-speed cable technology manager at Samtec New Albany, Indiana, feels that both solutions are equally reliable as long as they are properly configured, otherwise there will be problems. However, there are much less problems with cables. People know more about cables and have better backward compatibility.

Even so, Corning's latest progress may be able to reverse the previous situation and facilitate the fiber optic solution. However, experts have different opinions on whether the optical fiber solution can replace the cable once and for all.

Soubh said: "My opinion is that they will coexist until a technology wins, but currently I don't see any signs of this situation ."

However, Wontrop believes that optical fiber has a clear advantage, which determines that it will dominate the market. "Cable connections will continue to exist, but as the problem with the fiber optic connector is resolved, it is likely to dominate the market due to its inherent noise immunity ." He also said: "switching to optical fiber cables requires users to replace connector sockets, and they need to replace the FPGA chip on the circuit board or reprogram the chip to increase the speed ."

Data Sheet

There are many types of high-speed cable data, but the engineers I know agree with some of the more important types. Avnet IP & E Phoenix, Arizona) pat Wastal, senior vice president of Electrical Engineering, believes that attenuation, impedance, transmission latency, skew distortion, shielding effect, and capacitance are the most important specifications electrical engineers can obtain from their data sheets. Soubh recommends that the designer check the insertion loss, cable length, and anti-torsion life specifications as the starting point.

Cable Type

Although copper cables and cable frames are two basic types of high-speed cables, there are many different types of cables available with a large number of different options in each category. Some of the more common cable) solutions include micro-coaxial cable, strip cable with controllable impedance, dual-axis cable, and shielded twisted pair cable. Other cable types based on copper wires include parallel cables, four-axis cables, and the RG series microwave cables and Microwave Coaxial Cables ).

There are three types of optical fiber cables: Single-mode, multimode, and plastic optical fiber POF ). The single-mode is characterized by only one Z optical fiber. It is more expensive than multimode optical fiber, but it has a higher transmission rate and 50 times longer transmission distance than multimode. Low-cost POF is a low-cost option comparable to glass performance, but it can only be used for a short distance.

Some high-speed cables are also designed for signal, power, or data transmission. However, mixing all data together has inherent problems. As Wontrop said: "This is a good practice, but the common mode attenuation of high-power noise in signals and data transmission signals is not good) You must try to eliminate it ."

10GbE pressure

More and more products coming soon are specifically designed for 10GbE applications, and they rely heavily on wires and cables used to transmit data signals. Soubh believes that this pressure has put a lot of pressure on cable manufacturers, and manufacturers must now consider the entire system much more than before.

"Cable manufacturers must pay close attention to each component and strictly specify each component, each step of the cable manufacturing process must be qualified and continuously measured to ensure that no step deviation or non-compliance with strict handling requirements." Wontrop is more optimistic about this transition. "Most industrial applications do not need it, but once the time is right, users will come up with a way to effectively use the increased bandwidth," he said ."

Problems and concerns

Without considering the cable type used, the designer must be prepared to solve the inevitable problems that may suddenly occur in high-speed applications and environments. Wontrop mentioned some issues that designers are concerned about when designing high-speed cables, including the possible power loss caused by long-term operation and the elimination of peripheral radiation and conducting electrical noise, whether the cable housing can withstand the target environment and the compatibility of the terminal connector.

Shielding and Materials

There are many available shielding methods based on the cost of the application and the target. Including standard braided shielding, wound shielding, aluminum/polyester film, metal foil, Flat wire, aluminum/Polyester Film braided shielding or wound shielding combinations, metal foil and braided shielding or wound shielding combinations, A combination of double-layer braided shield, double-layer wound shield, and Flat Wire and braided shield or wound shield. For copper cables, the sheath material can be selected from PVC, ptfe fep), TPE, TPR, and halogen-free polymers. The center wire is usually made of silver-plated copper wires or copper tin.

Application

There is no doubt that many applications use or require high-speed cables. The packaging, printing and dyeing processes, semiconductors, and electronics industries all rely on high-speed connections, says Wontrop. "High-speed connections with a communication rate over 10 MHz are being applied to all industrial applications ."

Test　

Cable manufacturers will test their products in many different variables and environments. Soubh recommends electrical engineers to pay special attention to impedance performance testing, multi-channel insertion/return loss, delay, and skew distortion. Existing measurement methods should be used to ensure that this process can produce stable/consistent products.

1. Discussion on current load and economic section of wire and cable
2. Future Market opportunities in China's wire and cable industry