So what are RF Shields exactly?
RF shields are small metal cages (see photo) that used to block radio frequency interference (RFI) and electromagnetic interference (EMI), using a form of technology known as a Faraday cage.
Scientist Michael Faraday developed the method in the mid-nineteenth century, blocking electromagnetic waves using a conductive container.
The mesh, or shield, conducts the electromagnetic field around the outside of the container, preventing electromagnetic radiation from infiltrating and neutralizing its effect on anything within the container, in some cases an entire room or structure.
Why Do We Need RF Shielding?
Many of us remember a time when your computer or electrical appliance would make a buzzing noise every time your cell phone was about to ring. That was due to interference that was not blocked by RFI shielding.
The radio frequency which enabled the call to arrive at your cell phone was also picked up by components within the PC or laptop, causing it to react with a noise or a flickering screen.
This unwanted effect has led to RFI shields becoming an essential component in computers and most electronic devices, to ensure that performance is maintained at an optimal level and to protect delicate components from unintentional harm.
RF shields are also essential for use in certain equipment used in life-and-death situations. The most common example is the fuselage of an aircraft acting as a shield against lightning strikes, protecting both the onboard equipment and the passengers.
Another common usage of EMI shields is for lining an MRI chamber. MRIs work by sending a magnetic pulse through the patient and recording the feedback.
Any kind of electromagnetic interference would play havoc with the instruments and invalidate the results. But with adequate RF shielding, interference is no longer a problem. Similarly, medical devices like pacemakers require protection to function correctly, and even small malfunctions can be deadly.
How Are RF Shields Made?
RF shields must be made from a conductive substance since they work by conducting unwanted electromagnetic waves around themselves and into a purpose-built storage mechanism, wave distributor, or the ground.
Therefore all RFI and EMI shields are made from a metal or a combination of metals. The choice of metal will depend upon the shield's intended use, as each metal has different properties and is suitable for different situations:
● In the case of aircraft, weight is critical, which is why metals that offer a high strength-to-weight ratio are the best choice.
● For a medical device that is designed to be used within a patient’s body, the important factors are longevity and non-reactiveness, to ensure that the device will be both durable and safe. Precious metals can be useful RFI shield materials for these types of devices.
● When it comes to mass production, cost is often the prevailing factor, and the intended lifespan of the device being protected can be relatively short. For example, a mobile phone needs an RF shield to protect it from the constant bombardment of unrelated signals, but most cell phones are used for just two or three years. Tin-plated steel is the most common choice for RF shields mobile devices. It offers the necessary level of protection, as well as excellent anti-corrosive properties and high solderability, making it cheap and easy to work with.
There are also many different structural options for RF shields:
● A solid sheet or layer of metal can be used. This was the original RF shield, as Faraday used aluminum sheets to line the room for his early experiments.
● EMI shielding paint. The enormous increase in the use of mobile and IoT devices has led to an increase in the popularity of EMI/RFI shielding paints. These claim to block radiation, and they work to varying degrees, but they have also been known to block intended signals such as cell phone reception. The thinness of the shielding also offers only limited protection, and the cost of these paints is usually very high.
● The most commonly used structure for RF shields is a mesh or webbing. These offer high protection while minimizing production costs and keeping weight as low as possible. The tightness of the weave will depend on the usage and the expected wavelength which the shield is designed to protect against.
● In terms of manufacturing RF shields, the most common method is bending. However, Masach exclusively uses drawn production, which results in seamless shields. Drawing involves the use of tensile forces to pull or draw the metal to the correct dimensions. This makes the shield more stable and less prone to faults. The thickness of the shield is consistent throughout and it is less likely to be damaged during shipping or use.
In Which Industries RF Shields Are Used?
RFI/EMI shields have many uses and are incorporated into an endless number of both everyday devices and specialized equipment.
Although RF shields themselves are relatively simple as a standalone piece of technology, the function they perform is essential, protecting both lives and critical equipment, as well as ensuring that common devices perform optimally. These are just a few examples from various industries:
RF shields are incorporated into many different medical devices and are also used on a larger scale, for example in MRI chambers, as mentioned above. The EMI shielding enables these devices to operate as they are supposed to without the worry of external interference.
RF shield manufacturers can help at the development stage by providing shields of different dimensions and properties to ensure the perfect fit, both in terms of size and function.
Although in the past the fuselage itself was enough to serve the purpose of an RFI shield, it can only protect the aircraft from external radiation. Today, every person boarding a plane brings mobile devices with them. Incorporating RFI shields into the onboard equipment protects carefully calibrated instruments from any source of electromagnetic radiation, making it possible for passengers to use their devices safely.
Cars are similar to aircraft, in that the body of the vehicle is itself an RF shield, protecting the passenger from any possibility of electrocution, as well as protecting the increasingly high-tech instruments. However, in recent years, there have been attempts to reduce the weight of vehicles, to lower both production costs and fuel consumption, making cars a little more eco-friendly.
Switching out metal body parts for plastic amalgams makes financial sense, but has the disadvantage of reducing the shielding properties of the car's frame. To ensure that the electronic equipment continues to work optimally, RF shields are now being incorporated into many different vehicle components.
RF shields have become an essential element of everyday electronics, isolating devices so that they perform as they are supposed to, without interfering with each other.
As devices become more complicated and weight is considered an important factor, tech developers should work closely with RF shield manufacturers to find the correct shield for each component, ensuring they fit as unobtrusively as possible into the device.
Communication between devices is transforming the world we live in. This is most noticeable in smart buildings and smart cities, where the IoT and IIoT are growing.
As with mobile devices, the biggest issue is isolating the devices from interference so that they operate correctly. RF shields are used to limit downtime and make it simpler to fix problems.