Questions tagged [infinite-impulse-response]

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

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Discrepancy in frequency response of biquad filter (in Python)

I have written a simple biquad filter class but when I check its frequency response, I get different results with different methods. If I check it "empirically" (by taking the FFT of its ...
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Modelling and testing fixed point IIR filter with freeware tools

I understand from this other question that prior to implementing a fixed point IIR filter on a particular microcontroller target it's best to create a model using a DSP tool and compare the output to ...
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Combining multiple bandstop filters works only sometimes

for a school project, we were supposed to filter out 4 rogue cosine waves of a given frequency. I created a filter of my own by choosing zeroes and poles by hand. Here, I made 4 poles and 4 zeroes (...
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Butterworth filter poles

Hi, I'm looking at this textbook question and trying to get a better idea of exactly what its asking. For the processing to be real valued each pole would have to have a complex conjugate right? So ...
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Mapping of Classic Filters for Digital Filter Design

Of the four classic analog filter types: Butterworth, Chebyshev, Elliptic and Bessel- are any of these relegated to obsolescence for purposes of digital filter design in comparison to optimized ...
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Causal inverse of $h[n]=\delta[n]-\alpha\delta[n-1]$

Find the causal inverse of $$h[n]=\delta[n]-\alpha\delta[n-1]$$ we have $h[0]=1$ and $h[1]=-\alpha$ also $h[n]=0$ for $n>1$ From the formula $$ h_i[n]=\sum_{i=1}^n\frac{h[n]h_i[n-i]}{h[0]} $$ we ...
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Step response of bandpass fitler

I'm working on a virtual bass system and the signal flow is as follows Where NLD denotes the nonlinear device which introduces both odd and even harmonics, and z^-D is to compensate the group delay ...
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IIR design: SciPy CMSIS-DSP coefficient format

How do you reconcile Scipy.signal's IIR design with CMSIS-DISP's API? Scipy.signal outputs in one of 3 forms: Numerator/denominator Pole Zero Second-Order-Sections. CMSIS requires an array of length ...
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Why use a notch filter to implement a bandpass

I have seen in a few papers, for instance in this one, the following method : Find an initial "frequency of interest" (FOI) Filter the input signal with a Notch filter around the FOI ...
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Wrong result when realizing fixed-point biquad IIR filter

I'm implementing a fixed-point direct form I biquad filter with Q1.15 precision. I use fraction saving to improve quantization error. However, my function gives me the different results compared by ...
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Phase plot from impulse response function does not match that of the frequency response function

I have a first order linear filter $$ H(s) = \frac{1}{1+\tau\,s} $$ With the impulse response function, found using the inverse Laplace transform as $$ h(t) = \frac{1}{\tau}\,\exp\left({-\frac{t}{\tau}...
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Python FIR Notch filter applied on both + and - frequency but only need + frequency

I have posted a summary of what I am seeing, I just made a pulse train and testing a notch filter on it as an example only. I also have a complex baseband signal centered on 0 Hz, this complex ...
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Transposed direct form 1 vs Transposed direct form 2

I am studying IIR filters and their implementation. I am following the material published by Julius Orion Smith at Stanford. In particular, I am reading this page at the moment. It explains all the ...
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Understanding the Chebyshev2 Bandpass Filter Poles-Zeros Plot

EDIT This ended up being a bug with my plotting code :) I'm relatively new to using IIR filters, I wanted a bandpass filter for the 0.5Hz -> 5.0Hz frequency range and was looking at the zero-pole ...
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Chebyshev Filter design using bilinear transformation-2 methods-2 transfer functions-which is right and which is wrong?

I got myself a book after looking the advice from stackexchange, it has been so far helpful for me. But I got confused in this numerical given in the book. The other method is this-: https://www....
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What is true for a normalised filter?

Somewhere I am seeing $\Omega_c=1\;somewhere \; \Omega_p=1$ What is the truth? Based on the sources I have referred, I believe it is $\Omega_p=1$. But I am not sure.
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Getting different values for order of filter using Chebyshev method-:

Here are the 2 solutions. I am getting 2 different values of order of filter for the given question. Which is wrong and which is right? Or are both right? Please guide $|H(j\Omega)|=-20\log_{10}\...
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Digital IIR LPF Difference Equation from Transfer Function

I want a digital IIR filter with f0=225kHz and fs=53.125GHz. I can come up with the transfer function and plot it using Matlab. ...
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Butterworth Filter Transfer Function

Butterworth Filter frequency response is given as: $$H_a(j\Omega)=\frac{1}{\sqrt{{1+\left(\frac{\Omega}{\Omega_c}\right)^{2N}}}}\quad \text{where $N$ is the order of the filter}$$ and for the transfer ...
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Estimating reverberant time (T60) of an IIR filter

I'm learning a method to genenrate pink noise by filtering a white noise in this book, and the author mentioned an estimation of T60 given the coefficients of an IIR filter in the code that ...
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How to read the filter IIR design numericals specifications?

First of all I want to let you know about notations that I am using-: $\alpha_p$=attenuation factor of passband(in dB) $\alpha_s$=attenuation factor of stopband (in dB) $A_p$=Gain at passband edge ...
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Why does the Direct form I become our first choice for fixed-point implementation?

I heard that the Direct form II transposed is better for floating-point and the Direct form I is better for fixed-point. Is it true? I understand that DF2 and DF1T should never be used in fixed-point ...
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Determine transfer function based on a diagram with ai coefficients given

From a diagram with input $x(n)$ a summer and three feedback delay taps I get the difference equation... $$y(n) = x(n)+a_1y(n-1)+a_2y(n-2)+a_3y(n-3)$$ Then I am given values for ai coefficients. Case1:...
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How to find Lattice structure when k3=1?

I could not type this so I got a snip shot. Pardon me for that. Here k3=-1. That means the formula Here we will get x/0=∞. How to solve this question?
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What is the best concise mathematical notation for applying an IIR filter to a signal?

For denoting the application of an FIR filter with impulse response $\mathbf{k}$ to a signal $\mathbf{x}$ in time domain, we can use the convolution operation, i.e., $\mathbf{x}*\mathbf{k}$. What is ...
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how to convert the zeros of an odd order Chebyshev Type II from low-pass prototype?

My DSP book (Rabiner, Lawrence R., and Bernard Gold. "Theory and application of digital signal processing." Englewood Cliffs: Prentice-Hall (1975).) has the following transformations for ...
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Aritifacts of time-varying IIR filters

I'm doing something like spatial audio algorithm using IIR modelled HRTFs. At each frame I get a direction information with azimuth and elevation, and then I have to find or interpolate the ...
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What is a simple method, if any, to calculate a variable IIR filter for audio effects in real time?

Question edited based on first answer which raised a lot of good points about what problem I'm trying to solve. Also reordered some things to stick context of how I did this with FIR so far at the ...
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FIR filtering returns "static" signal

//PROBLEM I'm trying to filter EEG trials from an array in which each trail has dimensions [8x125] = [number of channels x samples@250Hz], but the resulting signal looks static and wrong. Why is this ...
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IIR Filter: check for limit-cycle oscilations

So I am studying IIR filters and I came to read about limit-cycle oscillations in IIR filters. From what I understand that are two type of oscillations granularity limit-cycle: when signal levels ...
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IIR Filter Stability

I have designed an inverse IIR high pass filter by inverting its transfer function B(z)/A(z) to A(z)/B(z). However, the inverse filter has a pole at z=-1. Is this filter considered stable (marginally ...
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Who first coined "Direct Form I" and "Direct Form II"?

I see "Direct Form I" and "Direct Form II" commonly in literature to refer to FIR / IIR implementation from the filter transfer function, and reference it myself, but where did ...
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Sinewave generation with an IIR filter (suggested books)

In this tutorial http://www.ee.ic.ac.uk/pcheung/teaching/ee3_Study_Project/Sinewave%20Generation(708).pdf an algorithm to generate a sinewave through an IIR filter is described. On page 2 it is stated:...
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Difference equation to FIR filter coefficients

I have a difference equation $$y[n] = y[n-1] + 0.5x[n] - 0.5x[n-2] \text{.}$$ According to this answer, the filter should have finite impulse response. I just can't figure out how to get the FIR ...
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inverse z transform performed on 6th order IIR filter

we are told to find coefficients and impulse response of IIR filter of order of 6. There are 6 zeros and 6 poles in the design. Pole and zero pairs are conjugate and poles are within the unit circle ...
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Frequency domain filtering: must filter coefficients always be conjugate symetric?

While trying to do frequency domain filtering of audio signals using windowed overlap-add methodology, I came across some pre-calculated frequency domain coefficients. I noticed that the coefficients, ...
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Digital Filters

If I want to remove the baseline drift in my ECG signal, which digital filter should be used without distortion and shift in my filtered output? What are the necessary things I have to look for the ...
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Reconstructing input from the output of a known discrete-time IIR filter

I have known discrete-time IIR filter. I pass a signal x(n) through the filter and obtain the output y(n). How would I design a filter to obtain x(n) from y(n)? In general, is it possible to design ...
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How to check if a signal is mainly composed of a few impulse peaks?

I am working on a problem that produces different types signals, and I need to detect the peaks after low-pass filtering, then find_peaks from ...
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104 views

Output power of a signal passing through an IIR filter

suppose I have the following discrete time signal $x\left(n\right)=0.7\sin\left(2\pi \times 623\:nT\right)$ where $N=4000$ and $T=\frac{1}{f_s}$, where $f_s=40$ kHz I pass this signal through a simple ...
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IIR implementation - RuntimeWarning: overflow encountered in double_scalars [closed]

I have implemented a butter filter in python using this function: ...
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What is difference between "Direct form" and "Normal Direct form"?

What is difference between "Direct form" and "Normal Direct form"? I was reading about filters implementations(structures) and found out both words "direct form"and "...
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How to apply the gain factor G to SOS coefficients when designing a IIR filter on sptool (MATLAB)?

After designing an IIR filter on sptool, I export the coefficients (SOS) and gain (G) into a .mat file. When filtering, we can use sosfilt(SOS, x), which results in the correct output but with the ...
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Recursive, non-recursive systems; FIR, IIR systems

I am confused with the classifications of an LTI system as recursive or non-recursive systems and FIR or IIR systems. I understood what the FIR and an IIR systems are, but is it correct to say that ...
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Practical IIR filter implementation

I'm trying to implement a digital IIR filter on an FPGA and would be happy for some inputs regarding the actual digital implementation. I don't have a lot of experience with FPGAs and digital filters ...
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How to implement a high pass filter digitally to remove the dc offset from sensor data

I'm trying to implement a high pass filter on sensor data to remove the dc offset. I'm aware I can subtract the mean of the data but I'm looking for a frequency domain approach. I've used the matlab's ...
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Implementing an IIR filter in Pytorch using RNN with no nonlinearity

Is it possible to implement an RNN layer with no nonlinearity in Pytorch like in Keras where one can set the activation to linear? By removing the nonlinearlity, I want to implement a first-order ...
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Digital lowpass filter causing aliasing

I'm writing a biquad filter program in C++, using the RBJ Cookbook as the source for the formulas. https://www.w3.org/TR/audio-eq-cookbook/ The lowpass filter that I've made seems to half work. The ...
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295 views

IIR initial condition / state meaning

I am studying filters, in particular the Infinite Impulse Response ones. I digged into theory and practice and I gain some decent knowledge on the topic. However, I can't really figure out or find ...
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How to find Cutoff frequencies (f1 &f2) for a narrow band pass filter for a particular central frequency?

This is a basic filter question I think. I want to define a narrow bandpass filter's cutoff frequencies (f1 & f2) for a particular central frequency (fc) in iir filter I think in this case ...

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