# Questions tagged [infinite-impulse-response]

Infinite impulse response (IIR) is a property of signal processing systems.

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### python rewrite lfilter (iir) with for

It's a beginner question, but useful to users from python - signal.lfilter, I was using lfilter from Find reverse one pole ...
499 views

### Find reverse one pole lowpass filter

I need to find a filter that revert the one pole filter of the current signal, a function using Python (or MATLAB) scipy.signal.filtfilt or ...
332 views

### How to obtain digital IIR filter coefficients for known z-plane zero-pole plot?

My clue is just to expand brackets and obtain coefficients of numerator and denominator of my transfer function. Am I right?
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### Design of a digital A-weighting filter with arbitrary sample rate

I want to A-weight a time series with arbitrary sample rate. An analog A-weighting filter is defined exactly by IEC 61672-1. But there's no definition for a digital filter. One method is to use the ...
566 views

### advantage of using impulse response function for LTI systems? [duplicate]

i have a discrete-time LTI system $L$ that takes input signal $x[n]$ and gives the output signal $y[n]$. since $L$ is LTI, $y[n]$ can be derived as a sum of shifted and scaled impulse responses of $L$....
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### What's the point of MATLAB's scaling array for secord-order-section filters?

I'm currently working on a project where I'm implementing different filter types (e.g. iirs - direct form 1, 2, transposed 1, 2, etc.). I just recently started attempting to implement a second order ...
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### IIR with asymptotic impulse response

I have plot some of the IIR filter's impulse responses and some of them are exponentially increasing, increasing, decreasing etc but some IIR's impulse response approaches 0. If for example I have an ...
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### Are circular buffers relevant to transposed direct form IIR filters?

I'm currently working on a project where I'm programming IIR digital filters. I have already finished the direct form 1 and & 2 implementations. When doing direct form 1 and 2, I was able to ...
538 views

### DFT in IIR filters

To further summarize, I want to create a function in matlab that finds the time domain signal $y(n)$ and its $n$ time components ($n=0,1,2,...$) given the numerator and denominator of a transfer ...
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### Is there a way to derive an FIR filter using an IIR filter?

I know there's a thread similar to this one here, but the OP is asking the reverse of what I'm trying to find here. I've done some research on the web with very few sources coming up with actual ...
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### Implementation of a filter in a software application

I have to embed a bandpass filter into a software application. All the signal processing will be done in 32 or 64-bit double precision. The filter coefficients for an IIR Butterworth filter are ...
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### Starting off an IIR with plain averages to accelerate slow rise time

A 1-term IIR can easily be started off with the first data point, instead of 0. For data that's all > 0, this ought to be better than starting off with y = 0 : <...
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### Two question about RBJ Peak filter

I'm new into DSP and Filters in general. Its the first step ahead I do from learning and using a 1-pole IIR basic Low Pass Filter. I'm about to implement for my VST audio application (using C++ and ...
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### Impulse response of a continuous time system

Question The impulse response of a continuous time system is $h(t) = e^{-t}u(t)$. When $x(t) = u(t - 1)$ is input to this system what is the value of the output signal $y(t)$ at $t = 2.34$. My ...
1k views

### Formula for Bessel low-pass filter coefficients

When I am filtering a signal in python, it has a built in function to generate bessel filter coefficients given a cutoff ratio and a filter order (number of poles). I am trying to translate this to C ...
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### Analytical way to generate an IIR that is the square root response of another IIR

For simplicity take the transfer function of a second order IIR in $z$-domain: $$H(z) = \frac {b_0 + b_1 z^{-1} + b_2 z^{-2}} {a_0 + a_1 z^{-1} + a_2 z^{-2}}$$ Is it possible to generate a new ...
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### Real Time Goertzel Algorithm

Why is Goertzel Algorithm considered a block algorithm? Given that my input is bounded, couldn't I just run it forever (taking every sample that comes out after some length N) given a big enough word ...
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### Shall a $1^{\rm st}$ order IIR filter include $x[n-1]$ term?

I have seen a $1^{\rm st}$ order IIR filter in the following form: $$y[n] = \alpha x[n] + (1 - \alpha) y[n - 1]$$ Such as: another post in this forum However, the filters generated by Matlab, such ...
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### Comparing with FIR, why does IIR always gives a bias error, when calculating signal DC?

I am trying the DC blocking function in matlab. The algorithm of DC blocking is to find DC of the signal first and then remove the DC value from the signals. Here are the codes I tried, which are ...
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### When input data into a low pass filter, are the first several data unusable?

For example, I want to feed a DC into a low pass filter. The the filter's first several output will not have the same DC value I want. Does it mean that I need to dispose first several results? How ...
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### How to design very narrow, sharp lowpass filters - Only DC needed?

I asked exact the same here one year ago: One year ago question I asked this question again here, because after one year, I have learned more about DSP and am thinking ways to improve it. Filter ...
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### Correcting Impulse Invariance Method

I'm trying to find out if the correction (Jackson, Nelatury, Mecklenbräuker) could improve the (IIM based) filter response near Nyqvist. Here's my c++ routine (which is used for to calculate various ...
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### Unexpected behaviour when using lfilter with initial filter delay multiple times

I want to filter a very long signal in smaller parts, therefor I am currently using scipys lfilter with an initial filter delay doing multiple iterations of: <...
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### Fitting an IIR filter to a complex transfer function

anybody knows of better ways to fit an IIR filter to a complex transfer function than Matlab's invfreqz.m? I'm implementing a little transfer function fitting ...
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### IIR filters with variable roll-off

I have a filter design problem in which lowpass filters have to be designed with varying roll-off. E.g: 2.7 db/ocatve or 1.4 db/ocave. See picture below. This is easy to achieve with a FIR filter, ...
221 views

### Phaser effect with feedback control IIR filter calculation

This question is possibly relevant to this one, but it's not duplicate as far as I'm aware. I'm trying to make phaser with feedback control as shown in the picture below: (Got it from here) First ...
I'm still learning DSP and referring to Oppenheim video lectures. In that lectures, differential difference equation is obtained for IIR filter design, in Lecture 14. \mathcal{L}[\frac{\mathrm d}{\...
If a have a causal IIR filter described by $H(z)$ and I sample it in $N$ equispaced values around the unit circle, I get a DFT of $N$ points. That DFT corresponds to $h[n]$ truncated in $n=N-1$ or to ...