Hi Roberto D,
When determining the root cause of Radiated Spurious Emission issues, it’s important to figure out whether the problem is derived from an intentional radiator or an unintentional radiator.
An intentional radiator RSE is commonly due to harmonics of the transmitted signal and thus are rooted in the transmitter of the wireless device.
Typical causes:
Local Oscillator Leakage
Signal Chain Non-Linearity
Amplifier Non-Linearity
No Filtering in Signal Chain
Mixing Products
An unintentional radiator RSE comes from non-transmitter sources and can be classified as everything else on the device.
Typical causes:
Oscillators (Clocks)
Memory Interfaces (DDR)
Microcontrollers
Display interfaces
Switching power supplies
A spectrum analyzer, shielded enclosure, low noise amplifier, and EMC probes can be used to determine the source of the radiator by probing different areas of the device within the isolated environment of the shielded enclosure. You can start with the transmitter off first to help narrow down whether the RSE is transmitter related; then with it on (and potentially pushing traffic) while you probe the device to locate the source. Once the source of the RSE is located, mitigation methods would involve PCB layout techniques, shielding, signal filtering, or some combination of thereof.
