Iir_filter does not work with specified feedback taps?

GNU Radio
1

Hi All,

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

I want the IIR filter works as:
y[n] = 1.8x[n] + 0.8y[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,

2

On Tue, Oct 21, 2014 at 8:08 PM, Alex Z. [email protected]
wrote:

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