For our customer we have developed a carrierboard. During pre-compliance Radiated Emission measurements there was seen the emission was quite high around 4GHz, a few dB over limit.
After investigation by using of a near field probe weakest point is around the RAM/traces:
Did you make a comparison test using one of our carrier boards? The test with nearfield probes is usually showing spikes with the frequency you see in the radiated emission test somewhere on the board but in most cases, this does not mean that there is a problem. e.g you will see a spike of 25 MHz over the crystal oscillator but it is most likely not the source of radiated emissions of multiple of 25MHz.
The diagram you send only shows the range from 3 to 5Ghz. Do you also see harmonics of this frequency in the lower band ?
i like to take a look at your carrier design.
can you sent the schematic to support.eu@toradex.com?
Or we can set up a Zoom call so that I can look at you design.