FIR Compiler coefficients determined?

[Altera_Forum]

How are the FIR Compiler coefficients determined? 

 Are they preloaded and then depend on what kind of filter you require?  I have looked int eh user guide but it doesn't say.  Thank you in advance.

[Altera_Forum]

normally a FIR filter is designed in a software package such as MATLAB. the coefficient list can then be imported into FIR Compiler and used in your FPGA. the MegaWizard also features a basic coefficient generating tool.

[Altera_Forum]

Hi thanks, I was just wondering if anyone knew the actual method it used. Like the windowing method etc etc

[Altera_Forum]

looks like there are only window methods in the MegaWizard: rectangular, Hamming, Hanning, Blackman.

[Altera_Forum]

Dispro25 (http://www.digitalfilterdesign.com/) is a handy little free but powerful filter designer that I find useful. If you have matlab it's better to use that, but if you are looking for free yet still usable dispro is fine as well. If you really get into using it a lot, look at a program called dosbox to not have to go to full screen mode.

[Altera_Forum]

wow that's old school. :D

[Altera_Forum]

Matlab has four main methods to get fir coeffs: 

 1) fir1 function depends on using the sinc time domain equation + your chosen window(boxcar means no window). You just enter the order, cutoff and optional window.   2) fir2 function depends on ifft of required frequency vector.    3) firpm function is iterative(formerly called remez) => equiripple for amplitude across pass and stop bands   4) firls function targets equiripple for power in pass band   In the last three: You enter filter order, frequency vector and amplitude vector and optional window. They also allow for weights.   Other methods exist for speciality filters e.g. firrcos for raised cosine shaping filter ...etc   www.trafford.com/07-1766 (http://www.trafford.com/07-1766)