# Questions tagged [infinite-impulse-response]

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

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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 ...
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### 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 ...
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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 ...
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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 ...
1 vote
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### 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 ...
1 vote
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### 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 ...
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### 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. <...
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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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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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 ...
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### 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. ...
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### 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. ...
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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 ...
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### recursive, systematic convolutional encoder with finite response

In an exercise, we had the following recursive encoder given: For which we should find an input sequence that generates an output with finite hamming weight (I see this question similar to a find ...
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### 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 ...
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### 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. ...
480 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. ...
1 vote
120 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 ...
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724 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. ...
164 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 ...
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### How to Find Elliptic IIR Filter Order?

Can anyone explain to me how to use this equation to find the Order? Let's say $$\Omega_p/\Omega_s =0.509$$ and $$e/\delta = 0.00349$$ How can I find the Order? I'm so lost i don't know how to use ...
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### Matlab IIR stopband filter attenuates my sinusoid input with frequency in the passband

I'm a DSP newbie trying to get into the field. Despite being able to use some of the MATLAB tools, I'm still not completely solid on some intuition of the frequency domain. I've implemented a biquad ...
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### How to implement a 3rd order Butterworth IIR allpass filter with perfectly flat frequency response?

I'm working on an audio plugin which splits audio into frequency bands for individual processing. The filters must have zero latency, so no linear phase filters. I would like to have perfect ...
118 views

### digital Butterworth high pass filter

I am trying to high-pass filter a signal using a Butterworth filter, but I am getting the following results : As in the picture, there is no signal decay. python code: ...
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### Why are Some Filter implementations Preferable for Adaptive IIRS?

I am aware that some filter implementations such as lattice/ladder and SoS sections are advantageous over high order transversal filter structures in terms of coefficient update convergence in ...
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### Design the digital IIR filter with the following specifications

Lower stopband edge = 25 Hz Lower passband edge = 100 Hz Upper stopband edge = 225 Hz Upper passband edge = 150 Hz Stopband attenuation = 18 dB Passband ripple = 3 dB Sampling frequency = 500 Hz.
1 vote
326 views

### How to calculate IIR Lattice Filter Coefficients for Biquad Filter

If I have a biquad filter with known $a_1, a_2, b_0, b_1, b_2$ coefficients, how do I calculate the corresponding lattice/ladder coefficients? I have found information on deriving the lattice ...
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### How to calculate total added gain after IIR filter?

Let's say we have a white noise as input. Total RMS value is -20dBFS. When I apply a parametric filter at 250Hz with Q = 4 at 3dB boost, what will be the final total RMS of the signal? How can I ...
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### IIR Allpass Filter Phase Response Plotting in Excel

Using formula on Audio EQ Cookbook I implemented biquad IIR filters in Excel. As in my previous question Phase Response Function / Plotting in Excel (IIR Filter), Hilmar helped a lot with the phase ...
585 views

### Phase Response Function / Plotting in Excel (IIR Filter)

Using formula from Audio EQ Cookbook I implemented biquad IIR filters in Excel. I can now plot every transfer function and total of 8 band EQ with shelvings and peakings. My problem is, I can not ...
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### Approximate a Known System with Adaptive Filter and an Unknown System in a Series

I am using gradient descent on an adaptive IIR filter for the below system 1. At the moment I am just assuming the known system is not there and it works fine. However, occasionally when the known ...
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### iir filter saturation problems

I want to implement a IIR Band Pass Filter without using MATLAB functions. I get the coefficients as follows ($F_s$ = 1000, Band pass: 5-15Hz): ...
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I have a SIMO IIR filter represented as a state space system. I'm wondering if there is a canonical way of converting a IIR filter into a MIMO system, so I can calculate $N$ terms as input at once and ...