filters on FPGA
Hi,
It all depends!!!
One way as our friends mentioned before, you can use MATLAB (with SystemGenerator by Xilinx, DSPTool by Altera) to generate simple to complex DSP algorithms (including filters).
Another way is to use a DSP filter core provided with the vendor design tool (i.e. ISE, Quartus II, etc.). These cores are now days quite flexible at configuring a specific behavior of a filter. Of course this method is not as powerful as the first method, but for most part it does a good job. For this you can refer to the user guides for more information and finding out whether the capabilities provided by these cores are sufficient for your needs.
Another way, of course, is to code it in VHDL/Verilog in RTL form. This is really good for learning purpose, and getting hang of transforming a DSP algorithm (or filter in this case) to RTL code, and can be a quite interesting!! (and time consuming especially for adaptive filters!!) Also in scenarios of simple filters, it may give you a better speed/area result than the previous two methods due to the static overhead added to them for providing flexibility. For this you can look at the following book:
Also you can refer to the use guides of DSP cores for top level design ideas. Obviously, the knowledge of fundamental DSP is vital for best results. :=)
May I ask, what kind of filter design you are intending.
Hope this helps, and all the best.
Regards,