Strange output from openADC


#1

Hello all.

Recently, I’ve been doing some work with an openADC interfaced to an FPGA + SoC. I have been getting some strange results. No matter what I have for an input, the results hover around 0 and occasionally spike and saturate at some very specific amplitude (both positive and negative). See this picture for an example. I am directly feeding in a 10kHz sine wave into the board via the LNA port (I have also tried the port coupled with transformer and moved the jumpers, still no success). The spikes only occur whenever I am feeding in some sort of AC signal (amplitude doesn’t appear to change anything) Has anyone experienced behavior like this before?
image.png


#2

Hi Breadload,

Sorry about the late reply. You might be below the low frequency cutoff for the board. All the tests were done at 1MHz+, so try increasing the frequency of your input signal.

Alex