I'm trying to make a receiver front-end for educational purposes with a frequency range of 5kHz to 250kHz in the acoustic band. I have AD9649 (High speed, 20MSPS) and AD7357 (1MSPS, SAR) as A/D converter candidates. I am not familiar with communications hardware and I would need help deciding which one is more appropriate for my application. Also, regarding the ADC driver, I would like to know if there is any digitally controlled VGA that works on the kHz band. I've seen that AD604 does the job but I would prefer, if available, something digital for its ease of control.
Thanks for your help.