Most unmanned aerial vehicles (UAVs) require communications with ground-based systems such as radio gateways. Electromagnetic interference (EMI) can disrupt these communications, degrade the quality of global positioning system (GPS) reception, and interfere with the drone’s onboard compass, which is calibrated according to the Earth’s magnetic field. The causes of UAV EMI are numerous, but electrically conductive gaskets made of shielding silicones are part of the solution.
What causes UAV EMI?
Onboard a UAV, EMI can be caused by cross-talk between circuits or by the direct current (DC) motors that generate electricity. Beyond the UAV, sources of electromagnetic interference include cell phone towers, concentrated WiFi networks, high-voltage power lines, and buildings. Unlike traditional aircraft, which have several levels of EMI protection from individual line replaceable units (LRUs) to the overall fuselage, commercial UAVs usually aren’t designed to filter out significant amounts of radiated noise.
How are UAVs designed and used then?
By design, UAVs need to be small and lightweight. Cost is also a consideration, and it’s part of what makes UAVs an attractive replacement for manned systems. Defense and security applications for drones are well-known, but UAVs can also be used to inspect powerlines (provided that the drone isn’t exposed to high voltages) and pipelines. In addition, UAVs are expected to become an important part of the cellular architectures used in 5G networks for wireless broadcast and point-to-point transmissions.
Which UAV components need EMI shielding?
Many UAV components need EMI shielding. Examples include the radio controller and the radio receiver, the flight computer that’s connected to a telemetry radio and failsafe switch, the various servos or flight control actuators, and the pulse width modulated (PWM) amplifier chip that generates a current that switches between high and low output levels. Pitot tubes and pressure transducers, potentiometers, motor and avionic batteries, and the UAV’s inertial measurement unit (IMU) are also susceptible to EMI.
Why not just use board-level shielding?
Electronic Design reports that EMI shielding at the printed circuit board (PCB) level is part of the solution. So are thin specialized coatings like the ones used with mobile phones. However, many UAV components are housed in enclosures where there are gaps between mating surfaces. To fill these gaps, elastomeric gaskets are used. Silicones are a good choice because of their temperature and environmental resistance, and these elastomers can be filled with metal or metal-coated particles to provide electrical conductivity and EMI shielding. Plus, silicones are available in softer durometers with good compressibility.
Are there different types of EMI silicones?
Specialty Silicone Products (SSP) makes EMI elastomers that use either silicone or fluorosilicone as the base elastomer. Fill materials include nickel-aluminum, nickel-graphite, silver-aluminum, silver-copper, silver-glass, and silver-nickel. Several of SSP’s nickel-graphite silicones are flame-retardant and represent offsets to discontinued GORE materials used in aviation. SSP also makes EMI RFI silicones that are tested to MIL-DTL-83528, including multiple products with third-party shielding reports.
How are EMI silicone gaskets made?
SSP supplies EMI silicones as ready-to-mold compounds, compression-molded sheets, continuous rolls, or EMI extrusions. All of these materials are Made in the USA at SSP’s ISO 9001:2015 certified facility in Ballston Spa, New York. SSP’s shielding silicones support fabrication processes such as molding and die-cutting, and SSP also produces EMI RFI conductive O-rings. Several UAV manufacturers already specify parts made of SSP shielding silicones.