I have an input signal with bandwidth 2.5 MHz. Let's say it's filtered using analog Butterworth low-pass filter. I would like to sample the signal using AD9203 10-bit 40 Msps ADC. If I understand correctly, in this case 5 Msps is enough and I could use decimation to effectively increase number of bits per sample.
Is it enough to just add up every 8 samples @ 40 Msps on input and push resulting 13-bit sum @ 5 Msps to the output? Or a little more sophisticated processing is required?