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Questions tagged [infinite-impulse-response]

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

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ECG analysis in MATLAB

I'm working on a little project involving digital filters and DFT, what I want to do is, given a sampled ECG, get the heart rate using power spectral density. I got the samples from this database. ...
minghierid's user avatar
1 vote
1 answer
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How do you filter a signal, split in batches, using an IIR filter?

I have a signal that is measured by an optical sensor that is connected to an ESP-32. I am trying to apply a band pass filter "in real time" on this microcontroller. The signal is comming in ...
Theodore Gamaletsos's user avatar
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1 answer
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What is the sos simplification that octave does?

I am comparing sos (cascaded 2nd order IIR) coefficients from my own implementation of a textbook method versus the coefficients that octave generates. Here is an snip of the octave code: ...
mike919's user avatar
2 votes
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How to handle non-causality when decomposing a 4th order IIR filter into a parallel bank of second order filters?

What I am trying to do I am trying to code a Gaussian smoothing filter using the 4th order IIR filter described in Van Vliet's paper "Recursive Gaussian derivative filters". My code works ...
Omar Emara's user avatar
1 vote
1 answer
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Question about reducing phase delay in filters for microcontroller application

I am trying to design a filter to smooth out some of my sensor data. This is for a control systems application where I have limited phase margin. I am looking for a solution where I can maintain lower ...
Mr Phase Locked Loop's user avatar
1 vote
1 answer
57 views

The discrete-time impulse response of an IIR filter

Suppose you begin with the following model of a discrete impulse response: $$h[n] = \begin{cases} \displaystyle\sum_{k=1}^K \alpha_k p_k^n & n \ge 0 \\ 0 & n < 0 \end{cases}$$ i.e. a linear ...
DangerousTim's user avatar
1 vote
1 answer
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Initial conditions for 2 IIR causal filters applied to the same time-series consecutively

I have a buffer of shape (n_samples, n_channels) in which new samples are coming in at regular intervals and old samples are discarded. In this example, the buffer array is called ...
Mathieu's user avatar
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1 answer
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Group delay equalization for second order IIR notch filter

A couple of second order notch filters seem to be appear regularly in the literature (see e.g., Tseng, Chien-Cheng, and Soo-Chang Pei. "Stable IIR notch filter design with optimal pole placement.&...
rhz's user avatar
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IIR filter design for "data-aided" least-squares filtering

Consider a discrete-time signal consisting of a desired signal component and noise, as follows. $$y_k=d_k + n_k, \qquad k\in\{0,1,\dots,K-1\}$$ This signal is applied to a linear time-invariant (LTI) ...
rhz's user avatar
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Symbol Sync blocks in GNU Radio seem to use PID (well, PI) for their clock sync feedback loops. Why not IIR/FIR?

E.g. the Symbol Sync block has a Loop Bandwidth, which (if I read the source right) ends up as a PI loop. I know what PID does mathematically, and what FIR and IIR ...
Thomas's user avatar
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Best large gaussian filter for current SIMD instruction sets?

I'd like to make a faster version of the Gaussian blur for Inkscape. Here's what I found various open source projects use: librsvg: 3 box blurs when stdev > 2. Else, separable FIR filter. Krita:  ...
Yale Zhang's user avatar
5 votes
1 answer
188 views

"Tone Control" IIR filter coefficients

The documentation for Analog Device's sigmastudio shows some of the formulas behind their biquad IIR filter coefficients. The usual suspects (HP, LP, peaking, ...) as described in RBJ's cookbook are ...
playduck's user avatar
4 votes
1 answer
85 views

Connection between LTI filters and damped + driven harmonic oscillator?

In physics, a damped harmonic oscillator that is driven by a sinusoidal force has a steady state solution: $$ x(t) = \frac{F_0}{m Z_m \omega} \sin(\omega t + \varphi) $$ where $$ Z_m = \sqrt{\left(2\...
bluenote10's user avatar
3 votes
1 answer
152 views

Total energy of a digital filter's output from the current state

Let's say I've been feeding some digital IIR filter input samples $x[n]$ to get output samples $y[n]$. If after some time $t$ the input becomes all 0s, i.e. $$x[n] = 0, \; \; \forall n ≥ t$$ How can ...
cloudfeet's user avatar
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1 answer
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Audio EQ Cookbook Stability

I'm implementing 6 cascaded biquad peaking filters to make a 6-band EQ. In the system I want to calculate the coefficients on the fly (it's just gain thats changing, center frequency and BW aren't). I ...
Michael Beckwith's user avatar
2 votes
1 answer
91 views

low shelving filter frequency response diagnosis

I am building a second order modified biquad filter based on an implementation by Will Pirkle in "designing audio effect plugins in c++". However when I look at my implementation's ...
Brian Barry's user avatar
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0 answers
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Understand basic Impulse Response from Impulse, can you help me visualizing it?

I was looking at this graph from The Scientist and Engineer's Guide to Digital Signal Processing, copyright ©1997-1998 by Steven W. Smith: where basically it shows how differnt representations can ...
markzzz's user avatar
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2 answers
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Fixed point number scheme IIR filter with ADC

I am a student working with digital circuits. I just started a term project with someone else working on an ADC. I need to design a IIR filter in verilog. If the output of an ADC represents 1V by ...
Bowen Liu's user avatar
1 vote
1 answer
93 views

Allpass Filter with Sign Switch

I want to design a digital allpass IIR filter with the following transfer function. $$ H(\omega) = 1 \textrm{ for } \omega < \omega_1 \textrm{ or } \omega > \omega_2 $$ and $$ H(\omega) = -1 \...
Jiro's user avatar
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Why does an asymetric transfer function cause a non linear group delay?

I know that an IIR filter exhibits non linear group delay (so different frequencies can be delayed more) and that this is related to the fact that it is asymetric (due to considering previous outputs),...
thepman's user avatar
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2 answers
159 views

Total delay of cascade FIR filters

I have a doubt regarding the total delay in terms of taps for cascade filters. Imagine that I have an SOS IIR Filter (2 delays) and an FIR filter of 10 taps (10 delays) and another of 20 taps (20 ...
Gabriel Galeote-Checa's user avatar
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Bilinear transformation with a high sampling rate (chebyshev filter)

I'm trying to design a digital Chebyshev filter of order 2. This gives the general transfer function If I transform this and simplify I get If I then expand the denominator and then normalize so ...
Johannes's user avatar
3 votes
2 answers
527 views

Given two low-pass digital IIR filters, find bandpass coefficients

In the case of FIR filters it is easy to get a band-pass filter by subtracting the coefficients of two low-pass filter filters or by convolving a high-pass and a low-pass filter: ...
nopeva's user avatar
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2 answers
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IIR/FIR equations for custom frequency response

Given a frequency response plot where gain is 0dB up to Fc and after Fc gain increases linearly by factor K (example chart below): I am seeking how to arrive at its IIR/FIR equations so it can be ...
JCFS's user avatar
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1 answer
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Possible errata Proakis Digital Signal Processing Third Edition Figure 2.35c

I'm reading through the 3rd edition of John G. Proakis Digital Signal Processing and I came across a possible errata in Figure 2.35c on page 116. I couldn't find any errata sheet on the publisher's or ...
MikeM's user avatar
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1 answer
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How to trade poles of All pole filter with zeroes?

I have filter of order 2000 IIR all-pole. I want to implement it via cascade IIR filter. Is there any way to reduces poles order and increase zeroes as its cost. To balance zero and poles. Since all ...
mohammadsdtmnd's user avatar
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1 answer
120 views

Converting transfer function to cascaded IIR filter [closed]

I have two function, But I don't know which one is correct to convert my Transfer Function(tf) to secound order sections(sos). I'm using GNU octave, and it have intrinsic ...
mohammadsdtmnd's user avatar
1 vote
0 answers
118 views

Approximating fractional-octave Gaussian smoothing with non-causal variable-width IIR filters

I am trying to implement fractional-octave smoothing of amplitude response data with approximated Gaussian filters, as briefly discussed in this AES paper. Unfortunately, no implementation details are ...
butch_warns's user avatar
1 vote
2 answers
95 views

Is there a way to get this reverb effect working on something else than 44.1 kHz?

I have successfully implemented the Sony PlayStation 1 reverb effect, until I realized that it strictly works at a sample of 44.1 kHz. A quick web search shown that (as far as I understand), an IIR ...
aybe's user avatar
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3 answers
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Phase compensation using IIR allpass filters

As an exercise with IIR allpass filters, I am trying to compensate the phase of a lowpass Linkwitz-Riley filter using the Matlab integrated function iirgrpdelay. The code I am using is the following: <...
skateskate's user avatar
3 votes
2 answers
965 views

Why does scipy introduce its own convention for H(z) coefficients?

Conventionally, the definition of the system function for a IIR digital system is: $$H(z)=\frac{b_{0}+b_{1}z^{-1}+b_{2}z^{-2}+\cdots}{1-a_{1}z^{-1}-a_{2}z^{-2}-\cdots}$$ where coefficients are the ...
mins's user avatar
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1 answer
88 views

LCCDE filter classification

I am trying to figure out if $$y[n]-2.56y[n-1]+2.22y[n-2]-0.65y[n-3]=x[n]+x[n-3]$$ is either IIR or FIR, causal or non-causal, stable or unstable (BIBO). I got the transfer function from the ...
Andrew's user avatar
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3 answers
316 views

is $y[n] = y[n - 4] + x[n - 4]$ time variant or invariant?

I am confused about a solution because there is feedback. Let's introduce a delay parameter $k$ and rewrite the system equation as: $$ y \left[ n \right] = y \left[ n - 4 - k \right] + x \left[ n - 4 -...
Bikash Timsina's user avatar
1 vote
1 answer
107 views

Intuitive or physical explanation of DTFT$\{1\}=2\pi\delta(\omega)$

I am trying to understand the fact that "The DTFT of 1 (an infinite discrete sequence of unit impulses from from $-\infty$ to $+\infty$) is $2\pi\delta(\omega)$" in an intuitive or physical ...
Madavan Viswanathan's user avatar
1 vote
2 answers
103 views

Scenarios where Phase Response is (non-)problematic

In order to get a better feel for phase response and how it applies across the field of dsp, I'm looking for example scenarios where a filter's phase response is a concern and where it is not. Take ...
bazz's user avatar
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1 answer
103 views

IIR bandpass filter attenuates frequencies within the pass band

I applied Butterworth filters (order=5) that have different cutoff frequencies to a simple signal composed of four sinusoidal oscillations and computed its PSD. <...
scho's user avatar
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1 answer
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Non-causality deepness of inverse system

Assume I have a FIR, stable and causal system. I want to know the deepness of non-causality on the inverse of my FIR system. It's obvious that the system is non-minimum-phase, since minimum-phase ...
mohammadsdtmnd's user avatar
2 votes
0 answers
65 views

Can Synchrosqueezing be use to Derive IIR Filter From Impulse Response

I am looking for alternate solutions to determine the IIR filter coefficients from the impulse response, or more specifically determine the closest IIR filter for a given FIR filter. Much of this is ...
Dan Boschen's user avatar
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2 votes
2 answers
933 views

Why construct a minimum phase filter from measurements?

Sorry if this is a trivial question, but I am not doing signal processing everyday. I will try to express what I think I have understood as best as possible. Suppose I apply a (linear) sweep signal to ...
oliver's user avatar
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2 votes
1 answer
594 views

IIR Filter order vs group delay

From what I understand FIR filter order is same as it's group delay because of the linear phase and every frequency being delayed by same amount. For IIR filter, filter order only tells that filter ...
doubleE's user avatar
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1 answer
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design of cascaded biquad filter

I have to compare the response of an 8th order IIR filter and its equivalent 4 stage cascaded biquad structure. A sinusoidal signal is given as input to both the systems and the output responses are ...
Deepa's user avatar
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1 vote
1 answer
453 views

Difference between FIR and IIR filters

I understand that FIR filters have a finite impulse response and IIR filters have an infinite impulse response. Here's the issue: A signal is finite in time if and only if it is infinite in frequency. ...
Levi's user avatar
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0 votes
1 answer
252 views

Fixed point implementation of IIR filter

I am trying to implement an IIR filter followed by downsampler with the following specifications: fs=18000,order=8,3db freq=[500 1000],downsampling factor=6. ...
Deepa's user avatar
  • 315
0 votes
1 answer
107 views

BPF design as cascaded second order biquads

I am trying to design a bandpass filter in MATLAB with following specs: $$\texttt{f_s = 20000Hz}$$ $$\texttt{3dB freq = [392 464]Hz}$$ $$\texttt{filter order = 8}$$ When I tried to implement the ...
Deepa's user avatar
  • 315
2 votes
1 answer
320 views

What order of FIR filter is equivalent to an IIR filter for same design specifications and to get same magnitude response

I have to design a bandpass filter with passband frequency [300Hz 500Hz] and sampling frequency is 16kHz.The stopband attenuation required is 60dB.I have used butterworth filter in MATLAB to design ...
Deepa's user avatar
  • 315
1 vote
1 answer
140 views

Filter IIR, 1/3 Octave Corner with 2 Octave BW

I'm trying to design a new filter with IIR to filter out specific bands. Basically it's a bandpass filter with 2 Octave or 3 Octave bandwidth but the filter order should be equal to 1/3 Octave filter. ...
BugraKezan's user avatar
0 votes
1 answer
736 views

how to implement 0.05Hz high pass filter?

How is the high-pass filter with a cutoff frequency of 0.05 Hz(or 0.2 Hz or 0.5 Hz) implemented in Real time for ECG devices? What kind of filter or algorithm is used? The order of FIR filter is high. ...
Hamidof's user avatar
1 vote
1 answer
121 views

Tell FIR part and IIR part of a signal apart

I have been trying to figure out one of the homework assignments for my DSP class, and have been spending quite a lot of time figuring out a particular problem. The solution to this problem was given ...
Meow _J's user avatar
  • 15
4 votes
3 answers
953 views

Convert Sample Rate of IIR Filter Coefficients

I have IIR filter coefficients and zeroes, poles for that filters. But all filters are generated with 192kHz sample rate. I have no other info about filter properties such as Fc or filter type or Q. ...
BugraKezan's user avatar
0 votes
1 answer
235 views

Replicating scipy.signal.lfilter with initial condition using IPP

I am trying to rewrite some Python signal processing code in C++ and am stuck trying to figure out how to replicate behavior of lfilter with initial condition. The documentation for lfilter says that ...
yunyun333's user avatar

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