Sep. 30, 2024
RF shielding materials either absorb or reflect EMI radiations, ensuring the device is immune to RFI.
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RF shielding effectiveness is the figure of merit that qualifies the ability of an RF shield to attenuate the electromagnetic field.
The higher the RF shielding effectiveness of the designed shield, the less of an impact the RFI has on the electronic device or circuit.
Conductive or magnetic materials are used for RF shielding
The influence of the electromagnetic field can affect the performance of electronic circuits and devices. Because of this, it is critical to provide RF shielding to block or absorb electromagnetic waves from interfering with the functioning of electronics devices.
Usually, conductive or magnetic materials are used to make RF shields. The materials that have high RF shielding effectiveness include metal enclosures and Faraday&#;s cage. In this article, we will discuss RF shielding, its different types, and the materials used to provide the best RF shielding effectiveness.
The effect of electromagnetic interference (EMI) introduces disturbances in the functioning of nearby devices. When the electromagnetic waves disrupting the normal operation of electronics are radiofrequency waves, then the interference is called radio frequency interference (RFI). RFI can cause devices to malfunction if proper RF shielding techniques are not utilized.
RF shielding protects devices from the exposure of unintended radiofrequency waves or electromagnetic waves. RF shielding materials either absorb or reflect EMI radiations, ensuring the device is immune to RFI. RF shielding also prevents radiated emissions from emanating from devices.
RF waves can influence the functioning of individual components as well as the entire system. Depending on the severity of the RFI effects, RF shielding can be classified into different types:
Component shielding: A component shield encases a component that is susceptible to RFI or radiating RFI.
Board shielding: A section of a PCB or electronic equipment can be encapsulated inside an RF shield to prevent the detrimental effects of RFI from reaching other circuits.
Cable shielding: The parasitic reactance in high-frequency circuits aggravates the effect of RFI in cables carrying analog or digital signals. Incorporating RF shields on cables can minimize the RFI in cables.
RF shielding relies on both the reflection and absorption of electromagnetic radiations. Reflections result in RF waves bouncing off the surface of shielding materials. However, sometimes this is not enough; reflections can be extremely harmful to humans, and in some cases, lead to death. Therefore, the absorption of radiation is much safer.
There are a variety of shielding materials, each with unique properties. To ensure safety, it is important to select the appropriate RF shield. Metals are excellent in blocking electromagnetic energy from interfering with a device's operation. RF shielding can be provided in the form of metal sheets, metal screens, or metal foams. Commonly used metals in RF shields are:
Copper: Copper RF shields can be easily manufactured into any shape. The high conductivity property of copper makes it an effective RF shielding material.
Mu-metal: Mu-metal is a nickel-iron ferromagnetic alloy. The metal possesses high permeability and is effective in shielding electronics from static and low-frequency magnetic fields.
Aluminum: Aluminum is used in the form of foil or an enclosure to shield against low-frequency radio fields.
One of the disadvantages of metal-based RF shields is that metals are heavy, rigid, and costly. These drawbacks can be overcome by materials that are flexible, light, and cheap. The RF blocking properties exhibited by certain paints, inks, coatings, resins, and fabrics can be utilized as an alternative for RF shielding in some cases.
RF shields weaken interference and protect electronic circuits. RF shields establish enclosures that provide a shield between the emitter and susceptor of interference, thus diminishing the electromagnetic field strength.
RF shielding effectiveness is the figure of merit that qualifies the ability of an RF shield to attenuate the electromagnetic field. The shielding effectiveness is mathematically defined as the ratio of electromagnetic field strength before and after the placement of RF shields and is expressed in decibel (dB).
RF shielding effectiveness can also be called electric field shielding effectiveness (ESE) since it involves the ratio of electric field magnitudes. The RF shielding effectiveness can also be determined by taking the ratio of magnetic field amplitudes before and after the RF shield placement, which is why it is also sometimes referred to as magnetic field shielding effectiveness (MSE). ESE is equal to MSE if the medium is air on either side of the RF shields with plane waves as the incident waves.
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RF shielding effectiveness is dependent on factors such as:
It is important to design RF shields with high RF shielding effectiveness. The higher the RF shielding effectiveness of the designed shield, the less of an impact the RFI will have on the electronic device or circuit.
Cadence offers tools that can assist in the design and 3D modeling of RF shields. Subscribe to our newsletter for the latest updates. If you&#;re looking to learn more about how Cadence has the solution for you, talk to our team of experts.
Radio Frequency interference can impair a device's electrical circuits from operating normally. The characteristics of the shielding material, the design, thickness, the electromagnetic frequency, and the magnitude of any discontinuities on the shield all affect how well RF shielding reduces interference.
Different devices respond differently to radio frequency interference. Communication and electronic devices may operate worse as a result of radio frequency interference. Radiofrequency interference is a common problem in electronics and is not fixed in the actual world. Electrical circuits can both emit and also be susceptible to radiofrequency electromagnetic impulses. The use of RF shielding protects equipment from the negative effects of RF interference.
The ability to reflect or block the electrical component of electromagnetic waves is made possible by a material's high conductivity. Therefore, the frequency of the electromagnetic wave, the geometry of the shield, and the material's conductivity and magnetic permeability all affect how successful the shielding is. For example, a material with a high magnetic permeability can provide low reluctance lines of magnetic flux, which is useful for absorbing and pulling magnetic fluxes around the shielding region. Some of the materials that are commonly used include:
In contrast to copper alloys and aluminum, steel and other ferromagnetic materials offer low-frequency magnetic field shielding. Depending on the type of steel, they have a variety of RF shielding plus mechanical qualities. Low-carbon steels have increased permeability and saturation points compared to high-carbon steels. The saturation point is the magnetic flux density a material can hold at a particular thickness.
Due to its superior ability to attenuate and absorb electromagnetic waves' magnetic and electric components, copper is the most reliable material for RF shielding. In addition, it is electrically very conductible. Since copper is simple to produce and can be shaped into a wide variety of desired shapes, copper-based shields can be relatively easily attached as radiofrequency shields to electronic devices. In addition to these properties, copper is resistant to oxidation brought on by the environment and is naturally resistant to corrosion.
In very corrosive settings, nickel silver, also known as copper alloy 770, is frequently utilized as a radiofrequency shielding material because it comprises various proportions of nickel, copper, and zinc. It works well for attenuating RFI in the mid-kHz to GHz frequency range. In addition, they are perfect for building RF shielding for MRI equipment, which is prohibited from using magnetic waves because they have a permeability of 1.
Some conductive fabrics are lightweight textiles coated or combined with metals, including nickel, copper, silver, gold, and carbon. Polyester, silk, cotton, and nylon fibers create conductive fabrics. These materials reduce RFI in confined rooms and spaces and have strong shielding efficiency.
Thin aluminum sheets block low-frequency radio waves. Electronic equipment enclosures can be made of aluminum to provide built-in RF protection. However, aluminum has a conductivity of between 50 and 60 percent less than copper. Hence aluminum RF shielding needs to be thicker to be as effective at shielding as copper.
Electromagnetic waves are made up of opposing electromagnetic and electric waves that oscillate. The wavelength and frequency of electromagnetic waves are used to describe them. The electromagnetic spectrum serves as a representation of these waves' continuity.
Electromagnetic interference occurs when undesired electromagnetic waves or impulses interfere with an electrical device's ability to work properly. It is frequently referred to as noise or electromagnetic noise. It is possible to categorize radiofrequency interference based on its duration, source, and bandwidth.
Artificial sources of electromagnetic radiation, which can impact nearby equipment and gadgets, are emitted by electronic and electrical devices. The unnatural causes of RFI are divided into intentional and unintentional sources.
Astronomical events like solar flares, lightning strikes, static electricity, dust storms, cosmic noise, and snowstorms cause RFI to occur naturally.
Continuous radiofrequency interference (RFI) describes the RFIs that a source constantly emits by radiation or conduction. In contrast, radiofrequency impulse interference happens suddenly or for a very brief period. Impulse RFI frequently upsets the voltage and current balance of linked neighboring devices due to switches and illumination. Both types can be produced from natural or artificial sources.
Bandwidth is the frequency range in which the RFI is present.
There is no single, discrete signal where the interference manifests itself. A natural or artificial source might cause several types of broadband RFI. The sun, which obstructs useful satellite signals from communication equipment, is a naturally occurring cause of this interference.
Some of the typical RF shielding methods are:
For the most positive outcome when purchasing RF shielding from a RF shielding supplier, it is important to compare several companies using our directory of RF shielding suppliers. Each RF shielding supplier has a business profile page highlighting their areas of experience and capabilities, along with a contact form to directly communicate with the supplier for more information or request a quote. Review each RF shielding business website using our proprietary website to quickly learn what each company specializes in. Then, use our simple RFQ form to contact multiple RF shielding companies with the same form.
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