03 Oct 2017

Electromagnetic Compatibility (EMC) Testing

Drones are everywhere these days, and the applications seem to be endless. Look over a busy highway and you might see a drone monitoring traffic conditions. Check out the shelves at the local store and you'll see toy drones for kids and advanced drones for flying hobbyists. There are proposals to deliver broadband internet to rural locations using a fleet of hovering drones. Drones are being used in many different types of environments, for recreational, commercial, and military purposes.

What kind of EMC testing applies to a drone? In many ways, a drone is just like any other device. It is a package of electronics, which usually contains a radio and a battery to allow for remote control. From this standpoint, drones are not much different from other devices and would be subject to the same EMC requirements as any other electronic device, depending on the country or environment where they are used. For example, the electronics used in a commercially available drone in the US would need to meet the FCC Part 15 Subpart B limits, while the radio used to control the drone would require FCC testing and certification. A toy drone used in the EU might need to demonstrate compliance to EN 55014-1 and EN 55014-2, along with the Radio Equipment Directive to cover the radio compliance.

Radio approvals in drones suffer from the same issues as any other device. Frequency spectrum is not always harmonized globally, and there is no unified regulatory approval process for a radio to obtain approval in multiple countries. Often the radio must be tested in multiple countries and applications for certification need to be submitted to each regulatory authority, which can cause delays for product launch. Care must be taken when selecting a radio for the drone, in order to balance the needs of the application, the range and reliability of the connection, and to minimize the amount of additional testing or product versions required for target markets and end users.

While drones are similar to other devices and can be treated the same, there are some differences. Since they fly, they present unique challenges when being tested in their operational mode. Thought has to go into each test setup to determine whether or not the engines need to be running for a particular test. For a radio test, they probably don't need to be, but for EN 55014-1 and EN 55014-2, some modes with motors operating would need to be tested. Some method of tethering the drone during the test is needed, and for immunity testing, it is important to consider how the drone will be monitored. It might be necessary to test multiple modes. Idle mode testing makes it possible to see if the drone will suddenly activate and start flying around or turn on its engines, which could be a safety hazard. Testing in a hover mode might allow the control electronics to be monitored for errors due to the EMC disturbances being applied. These considerations also come up when applying aircraft or military emissions and immunity standards, such as RTCA DO-160 or EUROCAE ED-14 or MIL-STD 461.

Drones present interesting challenges for EMC testing. Given the variance in their usage and in the global technical requirements, there is no "one size fits all" compliance solution for EMC testing for drones. However, all is not lost as the technologies used in drones have been handled by EMC standards for years, and by leveraging existing compliance approaches for similar types of devices, a robust drone EMC test plan can be developed.

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