Introduction to DO-160, Section 21 Radio Frequency Emission
Posted on March 15, 2018 at 11:04 AM
DO-160, Environmental Conditions and Test Procedures for Airborne Equipment published by the RTCA (Radio Technical Commission for Aeronautics) specifies test conditions for the design of electronic hardware in airborne/avionics systems.
This standard covers a broad range of environmental test conditions and test procedures in its multiple sections, for all aircraft types. Section 21 covers the emission of radio frequency energy to ensure the equipment under test does not emit RF noise that interferes with the operational frequencies of aircraft RF sensors.
| Equipment Categories | |
|---|---|
| B | Equipment where interference should be controlled to tolerable levels |
| L | Equipment located far from aircraft apertures and radio recevier's antenna. |
| M | Equipment located aperatures are electro-magnetically significant and not directly in view of the radio receiver's antenna. |
| H | Equipment located in direct view of a radio receiver's antenna. |
| P | Equipment located close to high frequency or very high freqency radio receiver antennas. |
| Q | Equipment close to very high frequency or GPS radio receiver antennas. |
A shielded enclosure or shielded room is used for testing. RF absorbers are to be placed at a minimum, above, behind, and on both sides of the EUT. Please refer to official standard for complete set-up requirements. A reverberation chamber may be used in place of a shielded room.
The applicable limit and scanning bandwidths/sweeps on the spectrum analyzer is set as follows:
| Frequenc Band | 6dB Bandwidth (BW) | Minimum Dwell Time (seconds) | Minimum Sweep Time for Frequency Band (seconds) | Minimum Measurement Time for Analog Measurement Receivers |
|---|---|---|---|---|
| 0.150 to 30 MHz | 1 KHz | 0.015 | n/a | 0.015 sec/KHz |
| 30 MHz - 100 MHz | 10 KHz | 0.015 | n/a | 1.5 sec/MHz |
| 100 to 400 MHz | 10 KHz | 0.015 | 9 | 1.5 sec/MHz |
| 0.400 to 0.96 GHz | 100 KHz | 0.015 | 1 | 0.15 sec/MHz |
| 0.96 to 6 GHz | 1 MHz | 0.015 | 1 | 15 sec/GHz |
- Conducted emission measurements are from 150 KHz to 152 MHz
- Radiated emission measurements are from 100 MHz to 6000 MHz
- At least 6dB below the category limit is desireable.
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