# Radio Frequency Interference, Its Mitigation and Its Implications for the Civil Aviation Industry
## 1 Introduction  
In an era defined by the rapid evolution of wireless communication technologies, the aviation industry faces increasing challenges from RFI. As modern Aircraft heavily rely on electronic and wireless systems for navigation, communication, and surveillance, the integrity of the radio frequency spectrum becomes critical for operational safety and efficiency. However, RFI, whether intentional or unintentional, poses a significant risk to these systems, potentially disrupting flight operations and compromising passenger safety. The Very High Frequency (VHF) band (118-137 MHz) and Ultra High Frequency (UHF) band (300 MHz-3 GHz) are the backbone of civil aviation communication and navigation systems. VHF is primarily utilized for air-to-ground communication, enabling seamless coordination between pilots and air traffic controllers. Meanwhile, UHF supports a variety of essential functions, including radar systems, transponders, and Instrument Landing Systems (ILSs). Despite strict management regulations, the growing proliferation of wireless technologies, such as 5G networks, Unmanned Aerial Vehicles (UAVs), and Internet of Things (IoT) devices, has increased the likelihood of interference within these critical bands. RFI can arise from a multitude of sources. External sources include terrestrial communication towers, 5G base stations, improperly shielded electronic equipment, and atmosphericphenomena such as solar flares or sporadic E-layer activity. Internally, onboard electronic devices, including malfunctioning avionics or improperly used passenger devices, can also contribute to interference. Natural sources, such as ionospheric activity or solar flares, can further degrade or distort signals in the VHF and UHF bands. Regardless of the source, the impacts of RFI on aviation systems are profound, leading to communication failures, navigation errors, and surveillance system malfunctions. For instance, interference with radar altimeters or GPS signals can disrupt flight paths, particularly during critical phases such as landing or take-off, where precision is paramount. Additionally, intentional electromagnetic interference (IEMI) carried out by malicious actors poses a growing threat to civil aviation. Such threats often involve directed high-power RF signals or electromagnetic pulse devices that can disrupt avionics. Interference may enter systems via front-door coupling (e.g., antennas) or back-door coupling (e.g., power lines, cabling, or structural seams), each requiring different mitigation strategies. According to [PERSON] et al. (2024) [1], the immunity of Aircraft systems must span a wide spectral range--from MHz to several GHz--to ensure resilience across all potential interference scenarios. These requirements are consistent with aviation standards such as RTCA DO-160 [2] and MIL-STD-461 [3], which provide test protocols for radiated and conducted susceptibility in airborne equipment. Mitigating RFI has therefore become a key area of focus within the aviation industry. Effective mitigation strategies range from advanced technological solutions to stringent regulatory measures. Filters and shielding techniques are integral to protecting onboard systems from interference, while spectrum management ensures that frequency bands allocated to aviation are protected from unauthorized or overlapping transmissions. Additionally, real-time monitoring and enforcement by aviation authorities play a crucial role in identifying and addressing interference sources promptly. Despite these efforts, significant challenges persist. The global adoption of 5G technology, for example, has brought renewed concerns about its potential to interfere with radar altimeters operating in adjacent frequency bands. Moreover, the increasing use of UAVs and IoT devices introduces complexities in managing the radio frequency spectrum, particularly in urban environments where RF activity is dense.