Hi ,

Simple Question : Why there is no IIR compiler in Vivado IDE? Why there is only FIR compiler? 

In fact, I am using ARTY 7 baord and facing the DSP slices limitation when using FIR filters (I need to use 7 filters in my design).


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Posted (edited)

IIR filters are more challenging for several reasons (bitwidth / coefficient quantization, internal gain boosting / biquad Q, limit cycles, nonlinear group delay, non-feedforward data flow, ...)
You will probably find that once you've gone all the way through a fixed point implementation, IIR filters are not as attractive as suggested by the MAC count.
Of course, they do exist and it may work just fine (depends also on the values of the coefficients you're trying to implement).

Your filtering problem from the other post had a fairly narrow passband and a huge stopband. This is very expensive use of a FIR filter...

If you use a more sophisticated (multirate) architecture, you'll be able to get the same or better filtering with maybe 1..5 % of the MAC count.

One approach is:
- design an inexpensive band stop that suppresses the alias band of the following decimation step
- discard every 2nd sample (said alias band folds over your wanted signal but we've made sure there is no significant energy)
- repeat the procedure as many times as possible
- design a final filter that provides steep edges and equalizes the sum of all earlier stages
The point is that the cost of later stages gets much lower because the sampling rate drops (you may actually find most of the MACs get used in the first stage, and the last one is basically for free thanks to the much lower sampling rate).

Now this isn't trivial, people like me get paid for this... fortunately there aren't (yet) wizards for everything.

Edited by xc6lx45

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