If we just need a FIR filter with cutoff frequency = 4MHz, and sampling frequency = 20MHz. We can use Matlab to generate the FIR filter coefficient. Last, we can use adders to implement this filter.(or multiply a number by a const).
But If we need a FIR filter with cutoff frequency range from 4MHz to 6MHz, how to inplment it without using multipliers.(just use const. multipliers)