While society’s dependency on Personal Electronic Devices (PEDs) continues to grow, airlines must consider the needs of their passengers, while simultaneously taking the necessary precautions for electromagnetic interference (EMI). Whether communicating, navigating, or entertaining passengers, technology is increasingly becoming an integral role in our lives. The use of wireless connectivity of our devices is also growing, so airlines will need to realize the importance of this growing trend.
The increased use of PEDs during flight threatens the functionality of critical devices used in flight operations. Radiation and conducted EMI interfere with the integrity of these systems. Cabling for in-flight entertainment can act as both a receiver and transmitter of signals, so airlines must ensure that the signals of these PEDs operate within the “dead zone of frequencies,” approximately 2.4 to 5 GHz. Fortunately, normal LAN wireless connectivity does not affect the operation of flight equipment.
A typical barrier to use against EMI is a twisted pair cable. Using twisted pairs reduces noise and assists in signal integrity within communication systems such as these. Signals get transmitted on both cables 180 degrees out of phase, cancelling the interference of one another. PEDs onboard the aircraft create noise, so using these cables reduces the impact of effects they create.
Shielding twisted pairs is the primary method to prevent the reception of transmission of radiated noise. By shielding twisted pair cables, we can prevent the reception of EMI and prevent the emission of radiation as well. This is the primary method for reducing noise in twisted pairs. Cables are shielded with foil, braid, or both. Proper shielding can finally be accomplished by grounding the cable with a low-impedance path.
When IFE is being used onboard the aircraft, filtering is also used to ensure that their signals do not become coupled with those of avionics systems. Filtering is particularly effective at eliminating a type of interference known as differential mode noise. This type of noise is especially problematic because it lies directly within the path of the transmission signal. Twisted pairs have very little influence on the presence on differential noise.
Power lines must also be taken into consideration when discussing the impacts of EMI. AC and DC power creates harmonic noise below 2.4 GHz and above 5 GHz, so airlines must ensure that the IFE onboard their aircraft are being properly filtered. Filtering can also be accomplished internally within power supplies. Additional filtering can also be accomplished within the power distribution system of passenger outlets. Poor filtering allows noise to interfere with crucial avionics systems.
Performing an EMI scan is the first step when deciding which filtering option, a user wishes to use. This determines the intensity and frequency of the noise being emitted. Different connectors offer these filtering options. The connector receptacles provide the best option to place filtering. By either filtering or shielding the receptacle, we are able to further reduce noise. Shielding the receptacle creates a low-impedance track to the ground, while filtering the receptacle minimizes RF windows. This may be performed at several locations within the aircraft at a given time and control units or nodes throughout the fuselage can be used to enable these functions.
Additional Solution: Optical Fiber
Fiber optic is a non-metallic cable, meaning it does not receive or transmit signals as traditional metallic cables do. This essentially eliminates EMI altogether. Although fiber eliminates the issue, it comes with tradeoffs. Optical fiber is much more expensive than its alternatives and much more difficult to repair. Their silica or plastic material is also unable to withstand the extreme temperature that metallic cables can. When considering all cost factors associated with metallic cables like filtering and shielding, optical fiber appears more desirable.
What Should Be Done?
Investing in preventative measures to reduce EMI is worth doing. Aircraft need to be operating efficiently in every aspect of their design. Whether improving the operation of engines operation or onboard Wi-Fi, airlines must continually improve efficiency of aircraft functionality. The demand for IFE accommodations will not go away, so airlines will need anticipate the effects of customers’ desires and prepare for them.
IFE Connector Component Availability
Air Electro is the aerospace industry leading IFE interconnect stocking distributor. We partnered up with TE Connectivity Deutsch to supply the high demand for DMC-M (EN4165, BACC65) single module series connectors.
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