Spurious conducted emissions for TX(STM32WLE5CC6)

[Electronica77]

Hello,

I have started to develop one LoRa end node around a STM32WLE5CC6 chipset(QFPN48).

My device is operating in EU868 band. While the device is transmitting, I acquire the data for the frequency spectrum with a spectrum analyzer. As you can see from the screenshot, there are unwanted sided-signals(spurious) around the central frequency(868 MHz). Specifically, both the lower side and the upper side are equally away 5 MHz from the central frequency.

What is your consideration for the possible root cause of spurious injection? Is there any way to block or reduce these spurious?

Thanks in advance,

Stavros.

[NAndreadakis]

This spurious is part of SMPS problem. To fix the problem disable SMPS or change the components of SMPS with more optimized ones.