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Visitor laura_lmaxi
Visitor
732 Views
Registered: ‎04-22-2014

DSP FIR problem with output signal

Hello

 

I am designing a digital FIR filter with using the DSP ip core, 50 coefficients. The filter works fine, the cut off frequency is what it supposed to, the problem I am having, is that if I increase the amplitude of my input signal too much, such as the signal will saturate, the output of the filter stays in the previous value, it is like the system will want to prevent saturation or overflow. Is this the case?

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3 Replies
Scholar jmcclusk
Scholar
724 Views
Registered: ‎02-24-2014

Re: DSP FIR problem with output signal

Did you specify "Maximum Dynamic Range" in the coefficient quantization options?   This prevents overflow internally.

Don't forget to close a thread when possible by accepting a post as a solution.
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Visitor laura_lmaxi
Visitor
716 Views
Registered: ‎04-22-2014

Re: DSP FIR problem with output signal

I did and I keep seeing the same issue

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Scholar jmcclusk
Scholar
705 Views
Registered: ‎02-24-2014

Re: DSP FIR problem with output signal

It's kind of hard to explain the FIR Compiler output, since it doesn't exactly give you source code to play with.

 

Try this filter I wrote here:

 

https://forums.xilinx.com/t5/DSP-IP-and-Tools/Help-converting-floating-point-coeff-to-fixed-point/m-p/852671/highlight/true#M7899

 

Plug in your floating point coefficients, and it won't overflow..   Promise.   It scales the coefficients so that it has unity gain at the frequency with the highest response, using the sum of the absolute value of the coefficients.

Don't forget to close a thread when possible by accepting a post as a solution.
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