EMC Reliability Test
EMC tests for interference immunity and emission levels in both air and contact (i.e radiated or conducted interference)
This is the test of product immunity to external interference sources such as in the presence of a strong electrical field, electrostatic discharge, or power line surges/lighting that comes from the power grid.
This is the test of product self generated noise that releases it's energy to the environment can be either AC line conducted emission or radiated emission.
Conducted emission is the test where device generated noise can propagate back to the power line for the AC wall outlet. Hence the test point is at the AC wall outlet.
Radiated emission is the test where device generated noise over the air. A test antenna placed at 3 m away from the device under test which is placed at 0.8 M above the floor is used inside an RF chamber.
This is what FCC (FCC Part 15 Subpart B:2018 Test procedure ANSI C63.4-2014) or CE is testing to make sure all product radiates under a certain safe limit.
Example of Conducted Emission Limit FCC_Part15. 107_CE_AC Power_Class BN
Test are done at Neutral and Line polarities.
15 KHz to 500 KHz needs to have a noise level dBuV (Quis Peak) from 66 to 56 and AV dBuV 56 to 46
500 KHz to 5 MHz needs to have a noise level dBuV (Quis Peak) < 56 and AV dBuV < 46
5 MHz to 30 MHz needs to have a noise level dBuV (Quis Peak) < 60 and AV dBuV < 50
Example of Radiated Emission Limit FCC Part 15.109 & ICES-003 issues 6 - 6.2 Limits -Class B
Frequency 30 MHz - 88 MHz @ 3m: < 40 dBuv/m (E-Field Strength)
Frequency 88 MHz - 216 MHz @ 3m: < 43.5 dBuv/m (E-Field Strength)
Frequency 216 MHz - 960 MHz @ 3m: < 46 dBuv/m (E-Field Strength)
Above 960 MHz @ 3m: <64 dBuv/m (E-Field Strength)
Note: Highest test frequency is based on the 5th harmonic highest generated frequency. In a common 5GHz wireless device, this generated frequency is 5850, which translates to 27.925 GHz.
Summary and Conclusion
Emission test tests radiation level for the device understand what starts from 30 MHz to 40 GHz (the upper boundry is defined by the 5th harmonic of highest device generated clock source)
Conducted test tests the noise in the form of ac voltage that propagates back to the power line via AC wall outlet. It starts from 15KHz to 30 MHz
Emission and Immunity are the most common issues associated with consumer electronics.
Note: there are more tests such as ESD, Surge, Harmonic current, which is specific to CE regulation but not FCC compliance, which is not discussed here.