On performing EMI scans for FCC certification of our end product, there are EMI ‘spikes’ seen around 2.2GHz. The narrowband continuous wave noise spikes move across ~30MHz. These appear to hold for approx 1 second at each center frequency and are not averaged down due to the duration.
The system is essentially idle and not performing any processor or radio activity.
Can you help identify what may be causing this, and if it’s adjustable in any way?
If this is due to an internal clock, can the center frequency be chosen to move quicker to reduce the average measurement?
Hi CraigR, it’s doubtful this is emanating from wifi as we employ a filter that cuts off the sidebands of the 2.4GHz signal. However it may be possible that it is related to a display or camera input or similar with a nominal frequency in the 750MHz range, as the third harmonic would be 2.2GHz.
Can you try disabling these inputs/outputs or similar and see if the EMI emissions persist? You should be able to narrow it down based on which functional blocks are active in your product’s design. If you have flex cabling in your system, you may want to try disconnecting those (or other external cabling that may be draped over the device under test) to see what impact they have on the emissions.