# Tagged Questions

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

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### Sound glitches using fft segmented convolution

I’m trying to build a binaural audio player, I'm using MIT Kemar c library to get the hrtf and a fft segmented convolution. It works on real time but the problem is each time I change the hrtf I hear ...
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### Generating blue/violet noise without FFT

I need noise with a high frequency bias for a realtime audio application, so I'm interested in things like blue noise or violet noise. Is there a way to generate such noise without using a FFT or an ...
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Adaptive IIR filters is not straightforward, and may be unstable. Many people say that adaptive IIR filters use less coefficients than FIR filters. What I'm curious about is how many coefficients can ...
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### Learning about inverse-z-transform and how to apply it to a rational transfer function

I have been studying IIR filters and know that a rational transfer function: $$H(z) = \frac {b_0 + b_1 z^{-1} + ... + b_N z^{-N}}{1 + a_1 z^{-1} + ... + a_N z^{-N}}$$ has a finite difference ...
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### How do I test stability of a MIMO system?

Let's say I have a system similar to two interconnected IIR filters described like this: \begin{align} x_1(t)&=a_{11} x_1(t-1)+a_{12} x_1(t-2) +a_{13} x_2(t-1) + a_{14} x_2(t-2)+y_1(t)\\ x_2(t)&...
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### Weighting function for output error IIR filter design

I noticed, when I try to fit filter coefficients to a given complex transfer function with the output error method, implemented for example in the MATLAB function ...
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### Causal and Non-causal filtering. Strange behavior

I'm trying to understand the behavior of a causal filtering exemplified by figure below. This behavior is making LDA (Linear Discriminant Analysis) misclassify our data, by clearly reverse the ...
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### Is there a method to calculate the maximum gain of a biquad?

Given an IIR expressed as a biquad: $$H(z) = {b_0 + b_1 z^{-1} + b_2 z^{-2} \over 1 + a_1 z^{-1} + a_2 z^{-2}}$$ Is there a way to calculate the maximum gain the biquad attains over the range $0$ ...
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### IDFT of H(z) sampled in N values

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 ...
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### Decimating physics data

At work we run a physics simulator (video game) that operates in an inner loop at 360 Hz. Data from that inner loop is collected 60 times a second and sent out to hardware (a force feedback steering ...
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### FIR estimator for IIR system

Suppose that we have a dynamical system of which the impulse responses are infinite (IIR). Now I found methods on papers (http://dx.doi.org/10.1109/9.839942) estimating states or outputs of such a ...
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### How do I find the phase response of a filter from the filter equation?

I am new to this forum. I have been teaching myself DSP for the last two years, so my experience and knowledge has a long way to go. I am trying to find the phase response of a specific filter that I ...
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### Calculating the product of discrete transfer functions

I'm trying to construct a higher order IIR from a biquad cascade, I know this is generally frowned upon, but it's necessary as the coefficients will be embedded into a larger formula used in a FDTD ...
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### Filtering an audio file using IIR filter on Matlab

First of all, sorry for my English. I'm quite lost with Matlab, I'm not comfortable at all and I have to create an IIR filter using Matlab. The thing is I'd like to remove background noise from an ...
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### Regarding BIQUAD IIR implementation in MATLAB

I want to implement a high pass filter (order 4) in MATLAB using cascade form. ...
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### Zero-Phase Algorithm in Matlab

From this document it's says 1.Filter the Data 2.Flip that 3.Filter again 4.and Flip that again for zero-phase filter. but when i do this in matlab , i'm compare ...
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### Are all IIR filters unstable in nature?

I know this question has been asked here numerous times. But I am still unclear here :( My book says, A linear time-invariant system is stable if its impulse response is absolutely summable. (G....
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### Convolution by IIR filter, a case where circular convolution is allowed?

The question is, how to attain the frequency domain representation of any signal (which is finite, non-unit length) convolved with an IIR filter. The correct answer in my opinion is that there is in ...
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### why difference between this example and matlab result

everyone fs=30 000 , fc=3000; when i code apply this in matlab result is very difference ...
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### There is a mysterious factor when compute coeffiencts

everyone i m trying write higher order butterworth algorithm in c++.I can compute nominator and denominator second order. So i tell myself , i can cascade struct for higher order. But there is between ...
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### Is the below filter linear phase

$$h(t) = \frac{1}{1 + t^2}$$ and is it IIR or FIR filter. I tried finding the Laplace transform of this filter to get the data flow diagram with 5 taps and T=2s, however, I am unable to solve this. ...
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### What is the correct way to apply multiple IIR filters to a signal in MATLAB

I am attempting to apply multiple IIR filters (one band-pass, one high-pass, and one low-pass;each with Fs of 44.1 kHz ) to a signal in MATLAB by using the ...
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### Why lattice-structured all-pole IIR filter becomes stable, if the k-coefficients satisfies $|k_i| < 1$? [closed]

Why the lattice-structured all-pole IIR filter becomes stable, if the k-coefficients satisfies $|k_i| < 1$? Anyone who can tell me the way how to prove it, would be so thankful for me :) ps. If ...
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### May a causal system depend on future values of its own output

For example, let's assume a system given as y[n]-9y[n+2]=x[n] I convert the difference equation to y[n]=(y[n-2]-x[n-2])/9 ...
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### Discrete-time Biquad filter: Relation between peak frequency and pole frequency

This question arose from a discussion in the comments to this question and its answer. The author of that question discussed a discrete-time second order filter described by the following difference ...
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### Overlap/Chunk processing possible with Zero-phase?

I'm relatively new to DSP and I'm currently investigating FIR filter and IIR filters. From what I've found FIR filters can be implemented efficiently using the overlap-save method, but I was wondering ...
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### Convert simple CT filter to DT with impulse invariance and bilinear transform

Can someone verify my work. Problem Question: Convert simple CT filter to DT with (A) impulse invariance and (B) bilinear transform  H_c(j \Omega) = \begin{cases} |\Omega|, & |\Omega| &...
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### Lynn's integer filter has a linearly increasing trend

I have a PPG signal sampled at 50Hz and I want to filter the signal using Lynn's integer filter. I.e $$H(z)=\frac{(1-1/z^m)^2}{(1-1/z)^2}$$ Cutoff frequency is 5Hz, so ...
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### How to compute DFT of IIR

This question pertains to frequency domain filtering. I'd like to multiply an IIR filter's frequency response by a buffer of samples that have been FFT'd. I get how I'd evaluate an FIR, I'd FFT and ...
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### How to estimate filter coefficients of an all-pole system?

Suppose we have measured the frequency response of a system that is known to be all-pole; measuring impulse response is not possible. What are the methods available, if any, to estimate the ...
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### How to shift the center frequency of an IIR filter

I have a pre-designed in-series 14th-order IIR filter in second-order sections. Problem is, when I simulate and measure the behavior in my codec, there is a frequency shift downward (as compared to ...
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### equations to calculate coefficients of recursive IIR Gaussian blur filter

I am reading the implementation of IIR Gaussian blur filter from this link. In the source code, the coefficients are generated by the following code ...
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### frequency response of Gaussian filter

In Matlab, the function freqz can produce frequency response in terms of transfer function and the function freqz2 can produce frequency response for FIR filter. It seems that I can's use the input ...