Hello!
I am looking for help with tracking down the cause of some unexplained spurious emissions we have been seeing from the CC1110 when it is operated around 433 MHz in our custom layout. We observe that when we transmit, spurs appear in a symmetrical manner around the carrier. The amplitude of these spurs changes linearly with that of the carrier - when the carrier power is decreased by 10dB, the power of the spurs does so. Backing off the transmit power from 10dBm to 0dBm does not help either. Below are some examples with an unmodulated carrier.
Carrier power 0 dBm:
Carrier power 10 dBm:
The GERBER files are attached below, while the full Altium design can be found here; gitlab.com/.../poc-gs-board
What are the reasons for these spurs? What can we do to get rid of them?
Thank you!