I am working on a digital down conversion module for a project of mine. The module down converts a signal at IF 455 KHz received through an ADC, multiplies it with a carrier generated through DDS and then low pass filters the final output. The final demodulated single of 3 KHz keeps pulsating with time.
I have attached a video sample of the following output. I would appreciate any kind of help regarding this matter. WhatsApp Video 2019-06-15 at 10.22.06 AM.mp4
You will need full debugging on all inputs/outputs from ADC to mixer to filter to observation tool. Otherwise it is all guess work. Pulsating waveform could be generated anywhere along.