Many electronic components today encounter Radio frequency interference (RFI) as a problem on a regular basis. Due to radio frequency interference, there is a great need to shield electronic components from any form of external interference. Furthermore, there are a wide range of RFI sensitive products and RFI manufacturers in the average household in today’s world.
Also, as new electric components are being introduced, there is an increase in the amount of electronic interference that goes around in the radio and electromagnetic frequency environment. One can say the exact definition of RFI is simply the amount of electronic noise or radio frequency radiation an electronic component or electronic device generates.
One of the things that make RFI a problem is that the range of frequency disrupts the capability for nearby electronic devices and equipment to function well. This is indeed a problem that needs solution.
What is RFI?
Radio frequency interference (RFI) is simply defined as the radiation of radio frequency energy. This radiation makes an electrical device to generate noise that disrupts the performance of an adjacent device. Also, RFI refers to the interference of the normal performance of a satellite as a result of the distortion of the radio astronomy.
Radio frequency interference (RFI) can interfere and disrupt the normal functioning of electronic and electrical devices, and as such it is crucial to reduce it when possible. Also, most electrical and electronic devices generate Radio frequency interference (RFI) is emitted. These include personal computers, medical instrumentation, switching power relays, game consoles, industrial controls, electronic printers, laptops, etc.
Electrical or electronic device generates RFI in two ways which are; conducted radio frequency interference and radiated radio frequency interference. In the case of radiated RFI, the interference emits from the device directly into the environment, whereas in conducted RFI, the interference emits into an AC power line via a device or component’s power cord.
RFI can occur naturally or intentionally in satellite communications. Also, various forms of space weather, such as solar storms, can make natural radio frequency interference to occur. However, when radio frequency interference is intentional, it is man-made interference.
Furthermore, RFI occurs due to unwanted RF energy in the system, this could manifests as data loss, equipment damage, and degraded performance. The RF source and receiver experience physical separation in electronic systems that have been affected by RF interference. However, unwanted electromagnetic signals generating interruption impact the proper performance of the device.
Also, the electromagnetic noises will become inductively coupled between the receiver and the source. This are popularly referred as radiated emissions.
How to Eliminate or Reduce Radio Frequency Interference
The occurrence of RFI in electronic circuits can be perfectly reduced or eliminated by three basic methods.
Shielding
You can contain RF noise and prevent any RF interference by simply enclosing the electronic system in a metal. In reality, you will have some radio noise leakage. Shielding is a great method of reducing RFI. Also, the impact of shielding increases when there is electrical bonding of the metal enclosure to the ground. When you wire through the shield, it can act as an antenna. Therefore, ensure wires don’t pass through the shield.
Filtering
Filtering is widely considered to be the most practical method of suppressing RFI. This method mounts filtering circuits across the terminals of electronic devices that generate noise. Electrical components such as capacitors and choke coils provide effective filtering.
Grounding
Grounding conducts RF noise away to the ground rather than emitting it as radiation.
Grounding, shielding, and filtering are the best methods employed to stop or prevent RFI in electronic circuits.
What is RFI Shielding?
Radio frequency interference (RFI) shielding helps to stop or prevent radio frequency interference. Also, it involves building an enclosure to minimize the amount of magnetic and electric transmissions from one space to another. RFI shielding protects electronic devices from radio frequency interruption problems that can impact their functionality and performance.
The majority of electrical and electronic devices generate radio frequency interference that could have an effect on other nearby devices. Also, a special surveillance device could capture the frequencies generated from such devices, this could compromise the privacy of the source in the long run. RFI shielding minimizes radio frequency radiation levels that enter or leave the environment.
RFI shielding design occurs in such a way that the range of frequencies filters under some particular conditions. Also, properly constructed and designed RF shielding can help to achieve a high degree of effectiveness. There are several factors that determine absorbance or prevention of radio frequency signals by the shielding. These factors include the conductivity of the material, the type of material used, the material’s permeability, and the material’s thickness.
Other factors for the shield are mechanical strength of the shielding and the amount of air flow to the enclosure. Copper is a very good material that offers more advantage in radio frequency shielding. It can absorb both radio and magnetic waves. Also, radio frequency shielding is often needed for corporate and government buildings. RFI shielding can offer a great solution, but it can be more cost effective when integrated with other techniques like grounding and filtering.
Types of RFI Shielding
The RF waves have the ability to impact the performance of the individual components coupled with the whole electrical system. There are different classifications of RFI based on the how severe these RFI effects are.
Board shielding
You can prevent the negative effects of radio frequency interference from reaching other circuits by encapsulating a part of an electronic equipment or a PCB inside the RF shield.
Component shielding
The component shield is a type of RFI shielding that encases the component prone to RFI as well as emitting RFI.
Cable shielding
The impact of RFI in cables carrying digital or analog signals increases due to a parasitic reactance present in the high-frequency circuits. Therefore integrating RF shields present on cables is a way of reducing the RFI inside cables.
Importance of RF Interference Shielding
The best way to protect electronics from RFI is RFI shielding. Also, RF shielding prevents electronic or electrical devices from producing emissions. RF shielding protects devices from getting exposed to unwanted electromagnetic waves or radiofrequency waves. Furthermore, RF interference shields are usually constructed with metal that encloses the sensitive circuit inside. A good example of RFI shielding integrated in electronic circuits is the Faraday’s. The materials for RF shield can absorb or reflect EMI radiations. Therefore, this ensures devices get protection from RFI.
Material properties like conductivity and permeability of the enclosure can change based on the RFI that needs mitigation. The type of circuit also influences the thickness and shape of the metal shield. The RF interference shield design is crucial because of the increasing market for electronic devices. Also, the high monetary losses resulting from RFI is also a cause for concern.
Transmissions between electrical or electronic devices result in unwelcome stress that may negatively affect their performance and functionality. These transmissions can jeopardize the privacy and security of the devices since their signals are open to interruption from external sources.
As a result of this occurrence, RF shielding in design is very important. Devices have the protective shield needed to reduce transmissions between different places. Also, this shield can prevent radio frequency interference when there is an enclosure around the application. Therefore, the environment of the application becomes safer and ensures that it functions well.
Types of Materials Used for RFI Shielding
RFI shields don’t have the same construction. This means that shields should to be custom constructed based on the electronic device’s design and application. There are many factors to consider during the design process. These factors include material thickness, galvanic compatibility, application environment, budget, and most especially, the material itself. The choice of the material for your devices determines how the devices perform. Furthermore, the material type determines the cost of shielding.
There are majorly three types of metal commonly used by electronic engineers. They include:
Aluminum
Aluminum is a great material suitable for a wide variety of applications since the metals feature non-ferrous properties. Also, it is widely known for its strength-to-weight ratio and high conductivity ratings. Due to these properties, this metal is highly recommended for RFI shielding. However, aluminum has some fabrication challenges, like oxidization and poor solderability.
Copper
Copper is a highly conductive material usually considered the most reliable and the best of all RFI shielding materials. This is because it attenuates magnetic and electrical waves. Also, copper is often integrated in MRI facilities and other crucial computer devices. This RFI shielding material is more expensive compared to the other shielding materials.
Pre-Tin Plated Steel
Pre-tin plated steel is a low-cost solution in cases of low frequencies in the kHz range. Also, this material provides excellent levels of corrosion protection. This helps to prevent rusting.
Common Causes of Interference
Interference results from unwanted radio frequency signals interrupting the use of electronic devices like television, cordless telephone or radio. Also, interference can prevent reception. It may result in a temporary loss of a signal, or it may impact the quality of the image or sound produced by your equipment. Transmitter interference and electrical equipment are the two most common causes of interference.
Transmitter interference
Communication systems that transfer signals that can generate interference are radio and television stations , amateur radios, and CBs. Design flaws like frayed or corroded wires, inadequate shielding, and insufficient filtering, may make equipment prone to transmitter interference.
You can determine whether a transmitter or electrical equipment is the cause of the interference by simply unplugging one household electrical device at a time. You can isolate the source of interference through this method. Also, if your device is responding to nearby transmitters like a CB installation or an amateur radio, there will only be interference when the radio operator is talking. You might not be able to hear a clear conversation.
Electrical interference
In case of electrical interference, you may only experience frozen pictures or intermittent audio while watching over-the-air television programs. Equipment around you like doorbell transformers, smartphone chargers, hair dryers, washing machines, sewing machine, computing devices, LED lights, and clothes dryers may be responsible for this type of interference.
Power lines can also cause electrical interference. Interference as a result of the electrical equipment of your power company is usually continuous. In this case, you must notify your power company. There is one simple way to determine the location of electrical interference. You can achieve this by integrating a small battery-powered AM radio tuned to a quiet frequency.
Applications that Require RF Shielding
There is an increasing need for custom-made RFI shielding as consumer electronics, home appliances, and automobiles integrate built-in electronics and smart features. Also, the following systems integrate custom-made RF interference shields to protect against RFI.
5G networks
5G technology is highly susceptible to RFI. This is because the majority of these networks rely on millimeter waves. Also, the development of 5G networks has to follow EMC regulations. Also, RFI shielding is integrated to achieve electromagnetic protection.
Military systems
Military systems integrate mission-critical data and as such any susceptibility to RF interference can make the data very prone to hackers. Furthermore, the RF interference shielding can be specially designed for military communication applications to prevent any form of data. Also, military vehicles need protection from RFI and EMU to ensure reliable and safe operation.
Automotive industry
The use of autonomous and semi-autonomous vehicles resulted in the design of several sensors and electronic components into vehicle architecture. To ensure a vehicle’s safe operation, the response of these electronics systems is crucial. Also, automotive networking integrates ethernet communication protocols to create data transfers using a central computer system.
Furthermore, non-metallic body components such as bumpers or panels are prone to any external RF noises. Some RFI shielding techniques are integrated in automobiles to allow the smooth operation of electronic systems.
Medical equipment
Sophisticated medical devices and equipment integrate the principles of electromagnetics. Therefore, interference could cause any glitch which could possibly cause the loss of human life. As a result, RFI shielding is strictly integrated in medical devices. This helps to prevent the malfunctioning of these devices due to RF noises.
What is RF Shielding Effectiveness?
RF shielding effectiveness is the capability of the RF shield in attenuating an electromagnetic field. Also, the RFI shielding effectiveness can be mathematically described as a ratio between the strength of the electromagnetic field before as well as after placing RF shields. Also, it is usually expressed in dB or decibel.
Furthermore RF shielding effectiveness deals with the ratio between the magnitudes of an electric field. Also, you can determine the effectiveness of RF shielding by simply getting the ratio between the amplitudes of the magnetic field before as well as after placing an RF shield.
Furthermore, RF shields can reduce interference and shield electronic circuits. RF shields create enclosures that offer a shield between the susceptor and emitter of interference. Hence, this diminishes the strength of the electromagnetic field.
What are the factors affect the effectiveness of RF shielding?
There are several factors that affect RF shielding effectiveness. Some of these factors include:
- The incidence electromagnetic field’s frequency.
- The RF shielding material’s permeability, thickness, permittivity, and conductivity.
- The distance between the shield and the emitter of RF interference.
- The electromagnetic field source type like the magnetic field, plane wave, or electric field.
- The quality of bond between the surface of RF metal shields
How to Design Effective RF Shielding
There are two main purposes shielding serve. The first is to stop interference and prevent eavesdropping, wiretapping, and electronic hacking. The function of the equipment within the shield will always indicate the type of shielding needed. Sensitive equipment needs protection from a nearby ambient interference. Also, high-performance shielding is crucial.
However, you might just need minimal shielding to prevent eavesdropping on classified data on a commercial computer. There are some factors that impact the exact level of shielding required. These factors include the sensitivity of the data being processed, the distance between equipment, and the type of equipment involved.
EMI and RFI are two types of radio frequency interference. Any electromagnetic radiation frequency can produce interference. Also, RFI occurs when the electromagnetic waves are in the radio frequency part of the electromagnetic spectrum. Radio waves have frequencies that range from 3 kHZ to 300 gHZ. EMI and RFI are terms that are frequently used interchangeably, EMI is more common. In terms of radio frequency spectrum, RFI is considered a type of EMI.
Difference Between EMI and RFI
EMI and RFI are two terminologies that refer to similar phenomena. However, RFI is usually regarded as a simple subset of EMI. These two terms are usually interchangeably used, and for good reason.
Radio frequency interference (RFI) usually refers to electromagnetic fields at radio frequencies. With more concern on higher-end frequencies used in radio products (100 MHz and higher). As regards this, RFI refers to radiated emissions. This is the reason the word “radio” is in the acronym RFI. Furthermore, electromagnetic fields generated from some source can emit noise in a victim PCB. This could measure as a conducted current in an interconnect or a circuit.
One can say Electromagnetic interference (EMI) is a general term that could mean radiated electromagnetic fields or conducted currents from a device. As regards frequency, the term “EMI” could also refer to noise around the frequency domain. This includes frequencies normally related to RFI. While higher frequencies are commonly associated with radiated EMI or RFI, a device could generate or receive radiated or conducted EMI at any frequency.
Although RFI is usually considered a part of electrical noise generated by any EMI source, it also refers to currents or radiation obtained from a narrowband RF source instead from a broadband source. According to some sources, RFI ranges from several kHz to about 30 MHz. However, in the reality, it is usually around anywhere up to very high frequencies integrated in wireless products.
How to Reduce RFI in Electric Structures
The RFI signals degrade the functioning of electronic circuits and equipment. Therefore, they are undesirable. Furthermore, they can make error rates increase and this could result in loss of data in data systems. Also, it could result in wrong measurements of electrical signals.
Furthermore, there are some regulatory requirements that regulate the highest amount of interference emitted by electronic equipment. But, it is equally impossible to have equipment or device that is RFI-free. The best thing a designer can do is to regulate and minimize the RFI, and as such preventing it from interrupting other nearby equipment. Also, you can prevent it from interfering with equipment sharing the same power lines.
Also, it is important that manufacturers protect their equipment from the interruption emitted by other equipment or from those that are nearby. Furthermore, they should prevent the RFI or EMI emitted from their equipment, from impacting nearby device or equipment or those that share similar power system.
One of the most effective and common methods that reduce the impacts of radiated RFI is shielding. Power line filters can reduce conducted RFI. This reduces the conducted noise coming out of the equipment. Also, the line filters prevents any incoming RFI.
Using RFI filters at the input of the electronic or electrical equipment is a design method that can help to reduce incoming interference and also preventing the interference from returning to the electrical power systems via the power code. Therefore, the RFI filter comprises passive components in a pass filter arrangement. This reduces the RFI signals by trapping them and as such, preventing the signals from entering or coming out of the equipment.
Conclusion
RF shields reduce or prevent interference and offer protection to electronic circuits. Also, RF shields create enclosures which offer protection between the susceptor and emitter of interference. Therefore, this reduces the strength of the electromagnetic field. In electronics, there are various classifications for RF interference shielding. This includes board shielding, cable shielding, and component shielding.
