In my application I've got the VGA followed by 12-bit ADC (differential signal). System works with IF signal which is undersample in ADC. Should I include any lowpass filter between VGA and ADC? (VGA and ADC bandwith is 10x more then my signal frequency). I ask because in analog devices adcs datasheet is mentioned that there should be no shunt capacitors on differential signals in IF undersample systems - i just dont know why.
My intermidiate frequency is 70MHz and VGA , ADC bandwidth is 800Mhz. ADC is driven by 56MHz clock if I recall correctly. So putting bandpass between VGA and ADC makes sense to limit noise vga ?