Recently, I encountered a thorny problem. Neither the software nor the hardware has changed, but 10% of the cards produced do not measure distance or the success rate of measuring distance is only half of the original. I found after test that the waveform of the continuous wave mode is the same as that of a good card when it is first powered on, but the waveform changes a few decades after it is powered on. The UWB schematic diagram of the card is as follows:
The waveform of continuous wave mode in the first ten seconds after power on is as follows：
The waveform in continuous wave mode is as follows ten seconds after power on：
Who knows what causes the spectrum waveform change？
Thank you in advance!