Radio Frequency Interference (RFI) is the disturbance or interference to the reception of radio signals. RFI occurs when the unwanted electromagnetic signal/energy emitted from an external source interferes with or impacts the reception of radio signals (or radio communication system).
The unwanted electromagnetic energy/signal emission from a source (e.g., LED lighting) that can disturb/affect a victim device (e.g., radio system or other electrical/electronic devices) is called electromagnetic interference (EMI). Hence, electromagnetic interference (EMI) is sometimes also called Radio Frequency Interference (RFI). The term Radio Frequency Interference (RFI) is usually used when electromagnetic interference e impacts the reception of radio signals.

Effects of radio frequency interference (RFI): 

Radiofrequency interference (RFI) causes the following Effect.

Communication Disruption: RFI can disrupt radio signals, leading to poor communication quality or complete signal loss. This is particularly critical in applications such as wireless communication, broadcasting, and two-way radio systems. For example, In an aircraft, during critical phases of flight (i.e., takeoff and landing), the use of portable electronic devices is prohibited. Since the unwanted electromagnetic signal (EMI/RFI) emission from portable electronic equipment becomes a problem for sensitive radio receivers in the aircraft. 

Data Corruption: In digital communication systems, RFI can corrupt data transmission, leading to errors, packet loss, or reduced data integrity.  

Degraded Signal Quality: RFI may cause distortion, noise, or other unwanted effects in radio signals, leading to degraded signal quality. This can affect the clarity and reliability of audio, video, or data transmissions. 

Malfunction of Electronic Devices: Electronic devices and systems can experience malfunctions or errors when exposed to strong RFI/EMI. This is especially relevant in sensitive equipment such as medical devices, navigation systems, and control systems.  

Safety Concerns: In critical applications like aviation or healthcare, RFI can pose safety concerns. 

What are the causes of Radio Frequency Interference (EMI)?  

RFI is caused by unwanted electromagnetic energy/signal emitted from an external source. Radiofrequency interference (RFI) occurs due to both human-made and natural sources. 

Human-made RFI sources include ignition systems, computers, routers, televisions, power lines, lighting systems,  Wi-Fi routers, cell phones, cordless phones, microwave ovens, GPS/cell phone jammers, unauthorized transmission, SMPS, motors, LED lighting, power line noise (broadband noise), AC/DC switching operation, workshop machine operation, automobiles & vehicles,  malfunctioning or improperly designed electronic devices, etc. For example, Electronic devices such as computers, routers, televisions, and lighting systems can emit unintentional radio frequency signals, contributing to RFI.  

Natural RFI sources include solar storms, solar flares, and cosmic radiation.
For example, Solar flares (highly intense electromagnetic radiation released from the sun’s surface) can affect satellite communication systems and cause HF radio signals degradation or complete absorption, resulting in radio blackout.  

Two ways of radio frequency interference emission:  

An electronic or electrical device can emit radio frequency interference (RFI/EMI) in two ways: Conducted radio frequency interference (conducted RFI) and Radiated radio frequency interference (Radiated RFI).
Conducted radio frequency interference: Here, unwanted electromagnetic signals (EM signals) or noise currents at radio frequencies emitted from a source (e.g., LED light) and propagated through the power cord or power line, connected cables, PCB traces, and associated circuits to reach/affect the victim device (e.g., other electronic device or radio receiver). The conducted RFI occurs when there is a physical conductive path (such as a transmission line or cable) exists between the source and the victim device.

Radiated radio frequency interference: Unwanted EM signals are directly radiated out from the device itself into the surrounding environment and reach the victim by traveling through space (air). Radiated RFI (also radiated emission) occurs when the source and victim device act as radio antennas. For example, poorly shielded or unshielded cables can act as an antenna and radiate electromagnetic energy, causing interference with nearby electronic devices or a radio system. 

How to prevent or mitigate radio frequency interference (RFI)? 

Mitigating Radio Frequency Interference (RFI) is crucial in maintaining the proper functioning of communication systems and electronic devices/systems. Here, some commonly employed RFI mitigation techniques are provided: 

Proper PCB Layout: Design printed circuit boards (PCBs) with care, considering signal paths, grounding, and component placement to minimize interference. Proper layout practices can help control both conducted and radiated interference. 

Good quality electronics usage: Use good quality electronics from reputable manufacturers to design and produce electrical and electronics products and radio communication systems. 

Grounding: Ensure proper grounding of electronic devices and systems. Proper grounding provides a path for unwanted electrical currents to dissipate, reducing the risk of interference. 

Filters: Install filters on power and signal lines to suppress high-frequency noise and interference. Common-mode and differential-mode filters can be used to reduce conducted interference or noise currents (conducted RFI/EMI) to a satisfactory and acceptable level. The filter prevents conducted noise currents from leaving an electrical and electronic device and from entering conducted noises from external devices via the connected power/signal line. Hence, the filters limit the conducted RFI emission from a device and enhance its immunity against the conducted RFI from the external device.  

Ferrite beads and Ferrite cores: The use of ferrite cores on cables can mitigate conducted RFI. Ferrite cores can be effective in reducing common-mode currents. 

Shielding: Shielding (metallic enclosure) acts as a Faraday cage and prevents radiated interference from both entering and emanating from electronic devices. Hence, the shielding limits the radiated RFI emission from a device and enhances its immunity against the radiated RFI from external devices. 

Isolation: Physically separating sensitive components or devices or moving away from potential RFI sources. For example, the use of Isolation transformers, optical isolators, and physical distancing.  

Shielded and twisted pair cables: Utilizing shielded cables for signal and power lines to prevent the emission or reception of electromagnetic interference. Twisted pair cables can also help to reduce RFI.  

Use of Fiber optic cable: Since fiber optic cables are immune to electromagnetic interference (EMI), they can be utilized as an alternative to copper cables. 

Compliance with EMC emission and immunity Standards: Electrical and electronic products shall comply with EMC standards to ensure the product will not emit intolerable RFI and properly function in its intended environment. EMC compliance products can minimize RFI/EMI interference on communication systems and electronic devices. Government regulatory bodies establish EMC standards and guidelines to minimize interference and ensure the coexistence of various electronic devices in the same electromagnetic environment.  

For example, FCC Part 15 is a United States EMC emission standard (conductive, radiated) for radio frequency devices (intentional and unintentional radiators). EN 55011 is a European Union (EU) EMC emission standard for Industrial, Scientific, and Medical (ISM) radio-frequency equipment. 

A product can get into/sell in the market of a country when complying with relevant EMC emission and immunity standards.