In our increasingly interconnected world, maintaining the integrity and reliability of electronic signals is more critical than ever. Whether it’s for high-speed data transmission, crisp audio-visual output, or sensitive medical equipment, ensuring that cables deliver their signals without interference is paramount. This is where cable shielding comes into play.
Cable shielding is a vital technology and, therefore, understanding the different types of cable shielding, how they work, and their benefits and challenges is essential for anyone involved in cable design or using electronic systems.
Join us as we delve into the world of cable shielding and uncover why it’s a cornerstone of modern electronic communication.
What is cable shielding?
Cable shielding is the protective layer, or layers, that is found wrapped around the conductors within a cable. It serves to block external electromagnetic interference (EMI) and radio frequency interference (RFI) from disrupting the signals being transmitted through the cable, or from the cable itself interfering with other nearby devices or systems.
What are the different types of cable shielding?
There are four main types of cable shielding; foil cable shielding, braided cable shielding, spiral cable shielding, and combination cable shielding. But what are they and why are they used?
1. Foil cable shielding
Foil cable shielding is a thin layer of aluminium or copper bonded to a plastic film, which is wrapped around the cable conductor. This type of shielding is commonly used in data cables, providing 100% coverage around the conductor, and is often used in high frequency cables.
2. Braided cable shielding
Braided cable shielding is done with woven strands of copper around the cable conductor, in a braided pattern. It is often used in audio cables, video cables, and radio cables at a low to mid frequency, for its high flexibility and strength.
3. Spiral cable shielding
Spiral cable shielding is similar to braided, but instead of being woven, the copper is spiralled around the cable conductor instead. This type of cable shielding is found to be most suitable for flexible cables – more so than braided cables – at mid to low frequencies.
4. Combination cable shielding
Combination cable shielding is done through a combination of foil and braided shields – typically with copper, or a combination of aluminium and copper. This type of cable shielding provides the benefits of both, 100% coverage, strength, and flexibility, often used in high-performance cables at all frequencies.
How does cable shielding work?
Cable shielding works by creating a barrier that blocks or reflects external electromagnetic interference (EMI) and radio frequency interference (RFI) from penetrating the cable and disrupting the signals being transmitted. It does this in four different ways:
1. Material composition
The cable shielding is typically made from conductive metal materials, or a combination of metal and plastic. These materials are chosen for their ability to conduct electricity and their effectiveness at reflecting and absorbing electromagnetic waves.
2. Electromagnetic interference blocking
When EMI or RFI waves come into contact with the cable shielding, the conductive material either reflects the waves away or absorbs them. This then prevents the unwanted signals from reaching the inner conductors of the cable.
3. Grounding
The cable shielding is usually connected to the ground (earth). This grounding provides a path for the absorbed or reflected interference to dissipate safely. By grounding the shield, any potential induced currents or electromagnetic waves are channelled away from the signal-carrying conductors and into the ground, where they can do no harm.
4. Containment of emissions
In addition to blocking external interference, cable shielding also prevents the cable from emitting its own electromagnetic signals. This is particularly important in environments with multiple cables and electronic devices, as it reduces the risk of the cable interfering with nearby equipment.
How to shield a cable: the cable shielding process
So now that you know what cable shielding is and how it works, how do you shield a cable? Cable shielding is a key part of the cable manufacturing process, but the actual process of shielding a cable is done in three steps:
Step 1: Check the core construction
The first step of the cable shielding process is checking the core construction.
So far, the cable should be formed with the conductor, or conductors, and the core insulation. This needs to be checked to ensure all is as it should be, before applying the shield. There are many benefits to wire insulation, so it is paramount this is all correct before moving forward.
Step 2: Apply the shielding
Then, the next step is to apply the cable shield. The process of doing this is dependent on what type of shielding your cable requires.
Foil shielding
For foil cable shielding, a layer of aluminium or copper foil is wrapped around the insulated conductors. This foil is often bonded to a polyester film for added strength and durability to the cable.
Braided shielding
For braided cable shielding, a mesh of copper strands are braided over the insulated conductors. This process is usually done by using specialised braiding machines.
Spiral shielding
For spiral cable shielding, a copper wire is helically wrapped around the insulated conductor. This is also often done by using a specialised machine.
Combination shielding
For cables requiring both foil and braid, known as combination cable shielding, the foil layer is applied first, and then the copper mesh is braided over the top of it.
Step 3: Cover with outer insulation
The final step of the cable shielding process is to cover the shielded cable with an outer jacket.
Known as cable sheathing, jacketing or cable extrusion, the shielded cable is covered with an outer jacket, to provide environmental protection and further mechanical strength.
Benefits of cable shielding
Cable shielding provides numerous advantages, especially in environments where signal integrity is crucial. Here are eight of the key benefits:
1. Improved signal quality
Cable shielding helps to block external electromagnetic fields, preventing them from interfering with the signal being transmitted through the cable – known as Electromagnetic Interference (EMI).
Shielded cables are also less susceptible to picking up radio frequency signals, also known as Radio Frequency Interference (RFI), from the surrounding environment – ensuring cleaner signal transmission.
2. Reduced crosstalk
Cable shielding helps prevent crosstalk, which is the interference that occurs when signals from adjacent cables affect each other, by creating isolation between cables. This is particularly important in densely packed electronic environments.
Furthermore, by reducing crosstalk, shielded cables maintain higher data integrity, which is critical for high-speed data transmission.
3. Enhanced durability and longevity
The shielding layer in the cables provides an additional physical barrier against physical damage; such as cuts, abrasions, and wear and tear. Shielded cables are also often more resistant to environmental factors; such as moisture, chemicals, and extreme temperatures. This protection and resistance helps to increase the cable’s lifespan, by making them more durable and reliable.
4. Compliance with regulations and standards
Many industries have strict regulations regarding EMI and RFI emissions. Using shielded cables helps ensure compliance with these industry standards, avoiding potential legal and operational issues.
Proper cable shielding also reduces the risk of interference that could affect critical systems, enhancing overall safety in applications such as medical equipment and industrial machinery.
5. Versatility in applications
There is a wide variety of industries that depend on cables, especially shielded cables – from consumer electronics to industrial automation, telecommunications, and medical devices. The versatility that comes with shielded cables makes them an essential component in many fields.
Furthermore, the different types of shielding (foil, braided, spiral, or combination) can be chosen based on specific needs, such as the level of interference protection required and the flexibility of the cable, making them even more versatile and adaptable across a wide range of applications.
6. Performance in high-frequency applications
Shielded cables are particularly effective in high-frequency applications, where unshielded cables would be more prone to interference and signal degradation. By maintaining signal clarity, shielded cables support high-quality audio, video, and data transmission, which is essential for professional and consumer applications.
7. Reliability in critical systems
Shielded cables provide consistent and reliable performance, which is crucial in critical systems where downtime or signal loss can have significant consequences. Due to their enhanced protection against interference and physical damage, shielded cables reduce the likelihood of cable failure, thereby minimising system downtime and maintenance needs.
8. Economic benefits
Although shielded cables may have a higher upfront cost, their durability and reliability often lead to lower maintenance and replacement costs over time.
Furthermore, reduced interference and signal loss made possible through shielding cables can improve the overall efficiency of systems, potentially leading to cost savings in terms of energy consumption and operational efficiency.
Challenges of cable shielding
While cable shielding offers numerous benefits, there are also several challenges associated with its use. Some of these challenges include:
1. Cost
Shielded cables are generally more expensive than unshielded cables, due to the additional materials and manufacturing processes involved. In large-scale installations, the cost difference can become significant, majorly impacting budget allocations.
2. Complexity in design and installation
Designing shielded cables requires careful consideration of the type and thickness of the shielding, which can complicate the cable design process. Furthermore, proper installation of shielded cables can be more complex, requiring specialised knowledge to ensure effective grounding and to avoid compromising the shielding.
3. Grounding issues
For cable shielding to be effective, it must be properly grounded. Incorrect grounding can lead to ineffective shielding and even increase interference. However, grounding requirements can vary depending on the application and environment, adding further complexity to the installation process.
4. Potential for shield degradation
Over time, the shielding material in the cable can degrade, due to environmental factors such as moisture, chemicals, and mechanical stress. Regular inspection and maintenance are required to ensure the shielding remains effective, which can add to the operational workload.
5. Electromagnetic compatibility (EMC) issues
Ensuring electromagnetic compatibility (EMC) in complex systems can be challenging, especially when integrating shielded cables with other components. Furthermore, improper grounding can create ground loops, leading to increased EMI rather than reducing it.
6. Environmental impact
The production of shielded cables requires additional materials, which can have a higher environmental impact compared to unshielded cables. The recycling process for shielded cables can also be more complex, due to the combination of different materials.
7. Compatibility with connectors and accessories
Shielded cables often require specialised connectors that can accommodate the shielding and ensure proper grounding. Ensuring compatibility with existing connectors and accessories can add another layer of complexity to the development process, and could result in higher operational costs.
Looking to explore cable shielding for your custom cable needs? Contact our expert team today for more information, or find more resources on our blog.
