Re: [Discuss-gnuradio] iir_filter does not work with specified feedback taps?

[Tom Rondeau]

On Tue, Oct 21, 2014 at 8:08 PM, Alex Zhang <address@hidden> wrote:

Hi All,

Any guys who ever used IIR filters? I got problems as below:

I want the IIR filter works as:

y[n] = 1.8*x[n] + 0.8*y[n-1]

Then I set the feed forward taps as [1.8], feeback taps as [0.8], just like 

self.iir_filter_xxx_0 = filter.iir_filter_ffd(([1.8]), ([0.8]), True)

But my testing result show that the feedback taps are not involved in computing at all, thus my output turns to 

y[n] = 1.8*x[n] 

I don't know anything wrong happened to my usage...

Need help. Thanks

--

Alex,

We use a convention where the first feedback tap is assumed to be 1.0. So you'll need to make your taps [1.8] and [1.0, 0.8].

Tom