Xilinx FIR Core Implementation

Randy Yates <yates@ieee.org> wrote:
>On 06/27/2011 10:39 AM, Andrew Ashworth wrote:
>> Hi,
>>
>> I've built a FIR filter in Matlab, and used to the coefficients in
>> Xilinx Coregen to build a multirate lowpass decimator (16x). According
>> to Matlab, and the Xilinx Coregen graph, I should be getting 120dB of
>> attenuation in the stopband. However, in real life when I hook my fpga
>> board to a signal generator, I only get around ~50dB of attenuation
>> between a tone in the passband and a tone in the stopband.
>>
>> I'm at a loss as to why this could be. Does anyone have any
>> suggestions on where I could start in order to troubleshoot this
>> issue?
>>
>
>I vote for precision issues.
>

afair the coregen filter generator will show both the ideal and the 
quantized filter response

it should be easy to check, it doesn't take many minutes to 
write and testbench that instatiate the filter and file in/output

-Lasse