Questions tagged [infinite-impulse-response]

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

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Cascading IIR filter with All pass filter (APF) for constant group delay and linear phase over the passband using MATLAB not working?

I've designed an IIR Low pass filter in MATLAB with the following parameters. ...
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How to implement an easy to use IIR-Filter in C/C++

Edited: I know there are some IIR filter implementation guides on the World Wide Web, however I can't find a simple guide on how to link simple PCM values to a digital filter. Most approaches are over-...
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Filter type selection for signal envelope detection

Working on a signal envelope detection code in Matlab in which an RF signal envelope is to be created. The flow is such that filtering is performed according to the detected presence of a signal in a ...
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How to create a frequency weighted measurement? / How to design a Pinking FIR Filter?

Disclaimer: I have read a lot about signal processing, but I taught everything myself and therefore have some gaps in theory and practice. I am currently working on a measurement software that is ...
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Calculating and controlling the location and bandwidth of individual notches in an allpass phaser

I'm currently working on a phaser implementation with the intention of adding some parameters that generate unique effects, namely effects that involve the precise placement of the phaser notches (e.g....
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Can sampling rate impact filter output?

I am noticing that the behavior of equalizers in music softwares varies depending on the sampling rate. If we apply a filter (IIR or FIR) to a digital signal, in what situations does the sampling rate ...
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Implementation of Deriche filter

The Canny edge detector is expressed by the derivative of the Gaussian. Its practical implementation involves the Gaussian filter, then the Sobel filter to calculate the gradient in both directions. ...
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Finite/Infinite Impulse Response filters

Most image filters are of finite extension (which correspond to Finite Impulse Response in 1 dimension), like Laplacian, Canny, Gaussian... Instead of being of infinite extension (IIR in 1D). Why is ...
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FFT-based fast convolution vs IIR filtering

I'm doing an multichannel audio equalizer system on a chip, which is parametric EQ, usually implemented in cascaded biquad IIR filters. My problem is that I use a lot of IIR filters due to multiple ...
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IIR Filter 3dB Frequency and Amplitude and Phase of output for given input signal

Hi I have some troubles in calculating the 3dB-Frequency and the output signal of an IIR Filter with a given transfer function $H_Z = \frac{1-Z^{-1}}{1+\frac{1}{2}Z^{-1}}$ Second question is to ...
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Designing of passband and stopband frequencies

good evening guys, let us consider following image we can see from the picture designing of lowpass filter with given passband region and stopband region, only one thing what i am interesting is ...
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What formulas do I need to add poles to these two filter designs

I am coding a music composition application and it uses a couple of different types of filter effects. I have implemented single pole, two pole and sinc filters to it successfully. I would now like to ...
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How to determined the cutoff frequency of a IIR or FIR

I am trying to design a IIR to remove the noise from my input signal. Here is my the my input signal in the frequency domain And here is the noise in the frequency domain that, So I may choose ...
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Does flat group delay bandwidth of a Thiran filter increase with increase in filter order?

Experimentally, it does seem that for a Thiran allpass delay filter of desired low-frequency group delay $D$ with filter order $N$, increase in filter order $N$ increases bandwidth of the frequency ...
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Stability of N-order Thiran delay filter when required passband delay is N+1

In this lecture note, on page 7 (or page 111, the same page), it is said that the Thiran allpass delay filter of order N with passsband delay N+1 reproduces samples with zero error. I find it hard to ...
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How should I pass a sequence of signal through a finished IIR filter in MATLAB

I am new to IIR filter. Lets say if my input signal is [1 -10 3 6 9], and the sampling frequnecy is $f_{s}=360Hz$, the cutoff frequency is $f_{d}=60Hz$, so the calculated $W_{n}$ is $0.4$. I just use ...
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what space of functions can be represented by the impulse response of an IIR?

I'm trying to understand the expressiveness of the impulse response of an IIR. For example, I know that second order causal IIRs are capable of having impulse responses that are growing or decaying ...
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Fixed-Point Filter Design: Where comes the DC-Gain difference between the bode plot and the step response from?

Introduction: What I wanted to achieve I am currently trying to implement a digital fixed-point filter on a STM32-Microcontroller by using the ARM CMSIS-DSP Library Link to reference manual. The ...
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Formula to compute FIR and IIR Filter coefficients

I am trying to understand filter design. I am trying to implement butterworth filter which would have high,low and bandpass using the difference equation representation for FIR and IIR. Given the low ...
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How to compute the inverse Z-transform

How to compute the inverse Z-transform of the form $$ G(z)=\frac{z^{2n}}{a(z^{2n})+b(z^n)+c} $$ I started by taking $$ F(z^n)=G(z) $$ so $$ \frac{F(z)}{z}=\frac{z}{az^2+bz+c}$$ This can be solved ...
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Question in DSP signal flow graph

How to convert signal flow in Fig3 to Fig4? Is these two equivalent? ZHANG Xiuli, ZHANG Ruihua, CHEN Weidong. Design of digital parametric equalizer based on second-order function[C]// IEEE ...
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Does FIR filter remove DC offset properly?

I was checking FIR and IIR filter for offset removal. But I found that FIR can not remove DC offset properly. I think there's something more to do with the filter coefficients of FIR to remove DC ...
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What could cause ripples in the output of an IIR filter fed with a pure sine wave?

I am using an IIR bandpass filter designed using the elliptic filter in matlab to filter out unwanted frequencies. The filter is fed with a test input that has a dc offset and sine wave of frequency ...
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What is the maximum output of an IIR filter?

I am implementing an IIR filter in an embedded device based on ARM. It is implemented as a cascaded biquad structure (series of second order filters put back to back). The filter can be considered ...
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IIR Filters H(z)=Y(z)/X(z) Why do we insert the coefficents of the input for Y(z)?

The System Function of IIR Filters is defined as $$H(z)=\frac{Y(z)}{X(z)}$$ The Output Signal as $$y(n)=\frac{1}{a_0}\left(\sum^{P}_{i=0}b_ix[n-i]-\sum^{Q}_{j=1}a_jy[n-j]\right)$$ I do not understand ...
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IIR System Identification Difficult Problem

Identifying IIR systems is considered a difficult problem and different approaches have been proposed. Why is it considered difficult? I would like to find an accessible discussion of the problem (a ...
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What would be the right interpretation of this IIR block diagram?

Will this block diagram always produce on the top-right arrow the following difference equation? $y[n]=x[n]+y[n-1]*(-2r)+y[n-2]*(-r^{2})$ Or by the contrary, it can produce also the following? $y[n]=(...
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4 votes
2 answers
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Using MATLAB's invfreqz to fitting a audio frequency response, but the result is bad at low frequencies

I am a DSP beginner. I have some audio frequency response (actually acoustic, especially speaker frequency response by the way) curves and I'm trying to fitting them by IIR filters using MATLAB's ...
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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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13 votes
3 answers
454 views

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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1 answer
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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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2 votes
1 answer
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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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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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