Yannick

@D@n I am totally agree with your explanations and the simulation shows exactly what I was expecting, of course. Yes, I believed that it was between -1 and 1 but when I read this (picture 1), I made the conclusion of the [-1/2 ; 1/2] range. I'm probably totally wrong (probably a misunderstanding as english is not my native language as you probably guessed ^^). My coefficients have 16 bits and the result of the multiplication as well, however the output width calculated by the FIR is 36 bits (picture 2) and finally, 40 bits as it is shown in the previous pictures of simulations (as it has to be a multiple of 8 if I well understood). My main question was how to interpret this 40 bits vector, so if I follow your reasoning, in the first case where the signal is filtered, the amplitude of the output near DC is 0 ? Besides, why do I have negative values with this 40bits vector ?

Oh, and why do I have a negative value in the filter_output... ?

@D@n, Okay, I understand some points ! But, I'm not sure to have well understood how to know the amplitude of the filter output. In the both cases here, I have 2 sine wave generated by a DDS, in unit circle mode which means, the range is [-0.5 ; 0.5]. Then, the two signals are multiplied. It gives me the signal called "result" with a [0 ; 1] range. Finally, this signal is low pass filtered (cut off frequency of the filter is 100 kHz) and I obtain this value on 40 bits which I don't understand. I don't know how to interpret it. Picture 1 : the 2 sine waves have a frequency of 100 kHz each Picture 2 : the 2 sine waves have a frequency of 20 kHz each

Hello, I'm building this filter, generating a .COE file in Matlab, which I use in the FIR compiler IP. Here are two screenshots of the settings. Do you know if the difference between the two pictures, in terms of magnitude, are just a displaying fact or if there is a real amlpification involved by the FIR compiler ? If it's the case, do you know how to fix it to generate the same filter as I designed in Matlab, so without gain ? Kind regards, Yannick