Questions tagged [infinite-impulse-response]

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

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Gain at critical frequency for Butterworth and Chebishev filters

In Chebyshev filter the critical freq occurs with gain Gp But in butterworth filter it is always at -3dB; why does this happen? Can anyone explain intuitively on this?
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Why does this parallel IIR filter have such a weird form?

Referring to "Parallel 1st-order IIR filters" on this wikipedia page, the structure of a 4-parallel IIR filter is discussed. However, the format in which it is implemented seems very odd. Why is it ...
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Difference in results between iirj and mkfilter with Butterworth filter in BandPass

When I generate a filter on www-users.cs.york.ac.uk/~fisher/mkfilter/trad.html and another iirj (github.com/berndporr/iirj) these are not the same results. Configuration (mkfilter): Type : ...
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constructing and initializing a normalized lattice filter using scipy

I'd like to implement a 2nd order bandpass filter in scipy using a normalized lattice architecture. (I'm choosing a lattice because it's guaranteed stable even when changing the coefficients on a ...
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Output length of an IIR Filter

In general, the output length of an FIR filter is given by (N+M-1) samples, where N stands for signal length and M stands for the number of filter coefficients. Can the same formulae be applied for ...
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Adaptive equalization vs inverse of transfer function

I have the following equalization problem as shown in the figure below: Now I can compute the coefficients for my adaptive FIR filter c (dim(c) = N) the following: $\mathbf{c_{opt}} = (\mathbf{H}^T\...
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Adaptive interference calcellation

I've got a question regarding an adaptive filter for interference calcellation: Here, the interference is a periodic signal: $x[n] = \cos(\pi/4\cdot n + \varphi_1) + \cos(3\pi/4\cdot n + \varphi_2)$ ...
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How do I normalize a predesigned IIR filter?

Obviously my question here is very similar to this previously asked question: How to normalize predesigned IIR filter coefficients to have unity gain? Unfortunately, in the responses available to ...
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Draw a structure for IIR Filter given H(z)

This is the transfer function for the Direct Form 1 of the IIR Filter: I'm trying to understand the rules to convert $H(z)$ into its corrispondent structure I've just understood how to draw $H_1(z)$,...
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Can I get some help plotting an IIR filter frequency response in Python?

The problem I'm trying to solve is described here. In my script, I used Euler's identity to calculate z^-n, such that z^-n = cos(omegan) - jsin(omegan). I find the magnitude of these values from a ...
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pressure decay filtering

So, I've been dealing with a series of pressure decay curves from a pressure transducer. Each one has a waterhammer effect as a consequence of shutting down pumps. Here are examples of 3 curves: I'm ...
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Preloading an IIR Filter

Is there a mathematical approach to initializing an IIR filter so that turn-on transients are minimized? Background: I have a high pass Butterworth design that overloads at the start of a sine wave ...
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To find the impulse repsonse using the difference equation

A causal linear time-invariant filter has transfer function a) Denote the input signal by x[n] and the output signal by y[n]. Find the difference equations for the filter. f) Find the impulse ...
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Impulse response of an infinite-length system

I have a system which is expressed as following: y[n] + $\alpha$ y[n-N] = x[n] where y is the output and x is the input. When I take the z-transform of both sides, I've found the transfer function ...
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Why can adaptive IIR filters result in unstable solutions?

For adaptive filtering, both finite and infinite impulse response (FIR/IIR) filters can be utilized. As an advantage of FIR filters in this context, guaranteed stability is often mentioned, while IIR ...
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Factoring digital IIR filter as a causal and anticausal pass?

Background: I'm new to signal processing and I'm reading some papers on B-spline interpolation of digital signals and trying to understand how a computation is derived. If I'm given samples from some ...
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FIR or IIR filter from poles and zeros

Is it possible to differentiate between FIR and IIR Filter just by knowing the poles and zeros of the system? If yes, how? If not, why? Thank you.
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Understanding a lowpass - comb filter implementation

I try to understand the implementation of the low-pass comb filter of the Freeverb reverberation algorithm: https://ccrma.stanford.edu/~jos/pasp/Lowpass_Feedback_Comb_Filter.html The original ...
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Lattice structure realization of an all-pole system

Given an IIR system with the system function, $$ H(z) = \frac{1}{2 + 1.4z^{-1} + 1.8z^{-2}} $$ I need to draw the lattice structure realization. I have drawn the lattice structure for $\frac{1}{1 + ...
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High order IIR Comb Notch Filter with small Bandwidth - Low atenuation of harmonics

Im filtering an EMG signal, more precisely the 50 Hz frequency and its harmonics. For that, I've constructed a comb notch filter (on filterdesigner in Matlab), with its fundamental frequency being 50 ...
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How to filter data with given numerator and denominator coefficients of an IIR Filter, in MATLAB Implementation

Coefficients are: b = [9.02201251375918 0.485095309463300 -0.571759308660462 3.63774928924158 4.42592447788520 1.30093840271037 -0.898592924453941 -9.08965268561448 -12.4939309921467 ...
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How would one design a (quasi) linear phase adaptive notch filter for a single complex tone?

While IIR notch filters are attractive, I need to retain phase linearity at the filter output. I imagine that it's possible to use a standard IIR notch filter: https://www.researchgate.net/...
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Vary poles/zeros of digital IIR filter

Many applications that produce sound, such as software synthesizers, are able to apply a filter that varies with time, such as applying a low pass filter that varies with an LFO. I currently have a ...
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IIR Direct FormII Filter second order in VHDL, false output

I am trying to implement an IIR second order in Direct FormII in VHDL. To make it easier to understand for me and to avoid former timing issues, I implemented the operations sequentially. In my ...
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Matlab IIR cheby2 bandpass, problems with Magnitude

I am trying to implement an IIR bandpass in Matlab. There are two things I don't understand. But first of all, let me post the code. ...
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Methods to evaluate the quality of an IIR Filter fixed-point implementation

I'm implementing a scattered look-ahead IIR filter in Matlab/VHDL, basically I convert an order-2 IIR filter into an order-4 IIR in order to take advantage of the pipelining of an FPGA. (reference ...
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Automotive Audio Question: IIR Filters and minimum phase

In a car, does matching the EQ of both the left and right side using IIRfilters mean that I'm matching the phase of each side? I have someone telling me that the car's environment is mostly minimum ...
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MATLAB Convolution

I am designing an IIR notch filter using pole-zero placement method. I am trying to convolve the two zero locations using ...
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Numerically Stable IIR filter

I am making an IIR Filter and I am running into problems with stability with higher orders. The values go off to infinity as soon as it starts. So far, I've been using MATLAB to generate my filters ...
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Jacobian Computation in Least Squares IIR Filter Design

Long time lurker and first time poster - but unfortunately I haven't had any joy untangling this on my own. I've been studying Mathias Lang's thesis, Algorithms for the Constrained Design of Digital ...
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226 views

Why Wiener filter not IIR

I would like to limit discussion to discrete time causal Wiener filter. By definition it is an FIR filter, and it also has optimality under Mean Square Error criterion within the class of linear ...
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Criterion to choose length of an accumulator and product

I am designing an IIR filter with fixed-point arithmetic and I have to select the proper length for the accumulator and product. I would like to know a standard to follow in order to choose its length....
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bibliography about implementation of IIR filters

I need to implement a 6th order IIR filter. The filter I need to implement is the A-weighting. I've simply used the bilinear function of Matlab with an fs of 20Khz. I need to implement this over the ...
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How to determine if an IIR filter is causal or non-causal?

It may sound impractical, as only causal system are passively realizable, but what I am facing is a general statement made regarding recursive digital filters: for them to be stable, the poles should ...
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Filter design for decimation of 1.1 kHz sensor sample rate to 100 Hz processing rate

Suppose, you have a signal source which is sampled by 1100 Hz and is "somehow" band limited to either 235 or 440 Hz. In my application, that's the ST IIS3DHHC accelerometer. There is an appnote for ...
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Calculating pre-history of recursive filter from state space representation when optimising for initial z

For a recursive filter, suppose a set of $b$ and $a$ coefficients have been calculated. Assume a state-space representation for which an initial set of $z$-values have also been calculated as in ...
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IIR filter with circular buffer - Arduino [closed]

I am trying to implement a butterworth lowpass filter with a circular buffer. The code below does not filter as intended and I am not really able to understand what is wrong. Any suggestion? ...
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Floating point to fixed point in C

I've been trying to make a digital filter. I've used the following transfer function to get my digital coefficients https://gyazo.com/00195ef119f0b2ff93fa5855715abdc9 Which i've then transfered to ...
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1answer
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Using Matlab's filter() function for solving difference equation with initial conditions

I am trying to solve a difference equation with initial conditions using Matlab's filter function: $$y[n]=\frac12y[n-1]+x[n],\qquad y[-1]=1\tag{1}$$ For $x[n]=6u[...
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Presenting an all-pass filter of a high order as a cascade of all-pass filters of the 1-st order

Are all-pass filter of the n-th order just a cascade of N all-pass filters of the 1-st order? There are some nice statements regarding zeros, poles, and gain for the 1-st order. Can those statements ...
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Protect an IIR filter from being reverse-engineered

I created a somewhat unique IIR filter and I want to protect the filter from being reverse-engineered I think you all know it is quite easy to get all the different weights of an IIR by using impulse ...
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Fast Recursive 1D Signal Smoothing - IIR / Auto Regressive Implementation of Gaussian Smoothing

I have just begun to dive into the field of signal processing, but there is the need to program a digital filter, that has to smooth a realtime signal from a sensor device. As far as I know, in my ...
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Digital filter design of time series for specified frequency response function

I am currently working with vibration measurements in structures. In the netherlands there is a guideline for verifying vibration measurements for damage to machinery. This is the so-called "SBR ...
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470 views

Explanation of FIR and IIR Filters with Simple Words

It seems I am unable to understand how these filters work and what is the point of using them, no matter how many tutorials I watched. Could someone please explain, in simple words, what FIR and IIR ...
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What version of sinc function to use ? (With additional factor of $\pi$ or not.)

I have an exam tomorrow on Signal Processing and one of the questions can go two ways: Use a Hamming window to design an Nth th order (N+1 tap) band pass FIR filter with a pass-band between $f_0$-$...
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Practical implementation of IIR/biquad filters following non-textbook transfer function of real-wold analog filter

I am trying to program a DSP filter to study prototypes of loudspeaker filters, which will be implemented as passive analog circuits in the final speaker system. This process involves simulation of ...
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Why is it easier to design an IIR filter in the continuous time domain than in the discrete time domain?

Given that the goal is to approximate the ideal filter with an IIR filter, why would it be easier to design it in the continuous time domain than the discrete? This paper says: Discrete time ...
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How to use the iircomb filter in matlab

I have a sound file that needs filtering which looks like this: Hence I think that I have noise spaced equally at 832Hz. i tried to use the iircomb filter taken from mathworks website and i managed ...
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Determine poles and zeros of a specific filter design

I have a design question and need to determine poles-zeros of a IIR bandpass filter. Requirements are: 1-order should be 3 2-causal 3-real valued impulse response 4-stable 5-cutoff freq: pi/3-pi/...
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Relation between order and stability in IIR filter

What is the effect of increasing order of IIR filter? does it also effects stability? If we have an IIR filter of order 6, now we change its order to 7, will there be any change in its stability?

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