i found some file in the web about the CIC filter design.i confuse the question:can we use the convolution to design CIC?
ep.in the matlab
R=3;
M=1;
N=5;
hrec = ones(1,R*M);
tmph = hrec;
CIC really is an implementation. The filter it describes is itself not that good. it is moving average to then Nth power. Huge amount of delay and generally poor filtering characteristics. But the implementation with fixed point math is insanely simple.
You can use filter/conv/filtfilt to perform a CIC filter in matlab. The performance won't be the same, but it can be useful to get approximate responses. again, the CIC filter will actually be implemented as a fixed point algorithm.