I am developing an application containing a GNSS module where the noise level in the power supply is a critical factor for the performance of the application. So much so that the GNSS module has a power system and an exclusive LDO.

I would like to read the noise level of the GNSS module power supply but there are some problems:

-> The noise level is generally less than 50mVpp. To accurately read such small voltages, you would need a very accurate reference onto the microcontroller's ADC (VDDA). What types of filters can I use? Is RC filter a good idea?

  • Noise components sometimes last a few hundred nanoseconds. How can I get precision in a measurement with such a small sample?

GNSS module: NEO-M9N Microcontroller: STM32F072

Another option would be some circuit that would only indicate me when I pass 50mVpp. But it has to be something fast enough to "capture" peaks of a few hundred nanoseconds.

Could anyone give any circuit tips or help on how to achieve this goal?

Note: I want to read the noise of the GNSS module. It is a separate power supply from the microcontroller.

Thank you so much

  • 2
    \$\begingroup\$ Why can't you measure it with an oscilloscope, do you have to do it in-system? \$\endgroup\$
    – Justme
    Feb 11, 2022 at 21:03
  • \$\begingroup\$ What frequency range of noise are you interested in A) Whats generated B) Which components matter? EMC standards? Depending on the answers you should measure the noise with a spectrometer or an oscilloscope first and then try to replicate the measurement in your own circuit. \$\endgroup\$
    – Ralph
    Feb 11, 2022 at 21:28
  • \$\begingroup\$ You imply that you are only interested in conducted interference from the power supply; what about radiated interference from the supply, microcontroller clock, or any other source? In my experience, GNSS problems generally aren't from conducted noise, especially if it takes the form of some few-hundred-nanosecond pulses; it needs a more-or-less continuously radiated signal to disrupt the correlators. \$\endgroup\$
    – jayben
    Feb 11, 2022 at 22:51
  • \$\begingroup\$ When the board is with me, I can use an oscilloscope. In the laboratory, noise is controlled. But the user might have a problematic power supply and my system can't handle the noise. The important thing is to identify conducted noise (peak to peak) from the power supplies (up to a few hundred nanoseconds). No problems with EMC. I don't think it's necessary to identify radiated noise, they are less problematic for me. I believe I don't need FFT, just indicate the peak-to-peak noise. \$\endgroup\$ Feb 14, 2022 at 11:35


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