order of the FIR filter - design code in HDL

FIR filter design code

when we are design a FIR filter in HDL language how can i determine the order of the filter and the designed filter is low pass or high pass.can i determine that from the taps used in the design and coeff.(filter function).and if it so what should be the order of the filter if the number of taps are 8.

FIR filter design code

Can you give more details?

Re: FIR filter design code

The order related to FIR filters simply is the number of delay stages (or taps). But it could represent very different filter types, approximiations of common analog filter as well as specific filters, that can only be designed in this technique.

Just to give you an idea how the design basically could work: If you have an intended frequency response, you can perform an inverse fourier transform on it and apply a window function. By particular measures you get a real valued only time series, and you have your filter coefficients. There are more sophisticated methods, but it basically works, I tried 25 years ago with an Atari computer.

More detailed description of possible design techniques can be found in lots of literature, numeric tools as MatLab or Octave as well as specific software can help you to design FIR filters. FPGA vendors have FIR cores for popular FIR filters, e. g. Altera or Xilinx.