Questions tagged [infinite-impulse-response]
Infinite impulse response (IIR) is a property of signal processing systems.
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questions
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How to find Cutoff frequencies (f1 &f2) for a narrow band pass filter for a particular central frequency?
This is a basic filter question I think.
I want to define a narrow bandpass filter's cutoff frequencies (f1 & f2) for a particular central frequency (fc) in iir filter
I think in this case
...
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34 views
Does my filter desing for unusual EEG experiment looks good?
I have made some progress since my last question, and again I am asking you for advice.
Hi,
I'm still designing an unusual (in terms of signal analysis) EEG experiment, which forces me to design my ...
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1answer
69 views
What is the relationship between group delay and propagation delay for a filter? [duplicate]
I was trying to design a filter for a system and I was able to obtain the group delay plot in matlab using grpdelay. The group delay output is in samples. However, I was not able to relate that data ...
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51 views
Matlab group delay not corresponding to reality
I studying effects of digital filters group delay (IIR). In Matlab there is a function grpdelay which allows for particular frequency get a value of delay in samples
But after filter applying and ...
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33 views
trying to reproduce the behavior of initial conditions for the filter delays of scipy lfilter with R
I'm trying to reproduce the behavior of lfilter and lfilter_zi (from scipy) in R (using signal package if possible).
This is the example provided by ...
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0answers
28 views
Stability of filters with negative phase delay, group delay, and positive phase
Lets assume I have an IIR filter with :
bz = [1.0195 0 0];
az = [1 0.0166 0.0020];
fvtool(bz,az)
The filter is stable as i can see.
If you check the phase delay ...
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1answer
25 views
Impulse Response for an Anti Causal Linear Shift Invariant System
I have a system given by
$$y[n] - \frac{1}{4} y[n-1] - \frac{1}{8} y[n-2] =3x[n] $$
I'm asked to determine the impulse response of both an anti-causal and a causal Linear Shift Invariant System ...
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37 views
How to design IIR digital filters
Practical Infinite-Impulse-Response (IIR) filters are usually based upon analogue equivalents (Butterworth, Chebyshev, etc.), using a transformation known as the bilinear transformation which maps the ...
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16 views
Stopband's edges in bandpass IIR filter in MATLAB
I've tried to get an IIR bandpass filter having the passband [0.1,0.5] Hz and working at the sampling frequency 8 Hz using the following command:
...
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23 views
What are the equations for magnitude plots of the common IIR filters? (Are the ones I have so far correct?)
I need equations that describe the magnitude plots of basic IIR filter types. I had looked into this a few years ago and saved some equations but it only covers part of what I need, and I can't recall ...
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1answer
39 views
Is there an equation that will graph the shape or predict the maximum amplitude of a single sample impulse fed through a One-Pole LPF?
If you feed a single sample impulse of a given amplitude through a One-Pole LPF you get an envelope that looks like this:
The output of the LPF from its peak will settle into an exponential decay ...
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30 views
what is purpose of IIR filter? [duplicate]
I am working on Digital Signal Processing. I know theory very well but I don't understand why IIR filter is used in place of FIR. What is advantage?
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58 views
Summation of two IIR filters
Actually my question is how to get the weighted average of two or three IIR filters given their transfer functions, which is nearly equal to this question. How to calculate the total transfer function ...
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1answer
163 views
simple iir filter implementation in C++
I am programming the simplest way of implementing and IIR filter. However, I am struggling with the use of buffers. Do any of you have any simple implementation of an IIR filter implementing manually ...
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2answers
63 views
When is the sum of two (parallel) minimum-phase filters also minimum-phase?
Say I have two minimum-phase filters:
$$\frac{A(z)}{B(z)} \: \text{ and } \: \frac{C(z)}{D(z)}$$
That is, the roots of $A(z)$, $B(z)$, $C(z)$ and $D(z)$ are all in the stable region.
If add them ...
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35 views
How to take multiple IIR filters efficiently
I have a collection of IIR filters (exponential decay at various decay rates). I'd like to compute all of them on a discrete time series efficiently.
Is there a way to do this that is faster than $$O(\...
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19 views
Yule Walker with Exponential Filters
I’m running an auto regressive model with IIR exponentially decaying filters.
Let $V$ be the input dataset and let $X_s$ be $V$ convoluted with an causal exponential IIR low-pass filter with decay ...
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How to compute autocorrelation with exponential IIR filter efficiently
I have a discrete dataset (called V). I want to compute the autocorrelation of V at multiple time horizons. Normally I know that I can use the IFFT of the PSD. But in my case I need it with ...
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2answers
207 views
How can initial conditions be taken into account to calculate a system's terminal value using the final value theorem or some other technique
I wish to calculate the Final Value of the following system given initial conditions not at rest, and assuming the X will not change from its initial condition value.
The transfer function is
$$H(z) = ...
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1answer
37 views
What does poles in unit circles center mean?
Suppose i have all my poles in unit circle center. What kind of information this gives me?
Can i determine if this filter is IIR or FIR?
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1answer
80 views
Approximation and IIR Filters
Consider the discrete-time time-invariant system with input $x[n]$ and
output $y[n]$ satisfying
$$y[n] = \sum_{k=1}^5{x[n-k]}$$
Consider approximating the desired system with a second-order IIR
system ...
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3answers
125 views
How to practically correct for group delay imposed by a digital filter (Python)
I'm using Python to filter a signal using a Butterworth filter (scipy.signal.butter) and subsequently passing this through a forward-backward filter with cascaded second order sections (scipy.signal....
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1answer
101 views
Frequency response of a digital state variable (Chamberlin) filter
I recently implemented a digital state filter based on the recommendation here. I've tested this filter's performance as a very low cutoff low-pass filter with limited coefficient quantization ...
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2answers
94 views
Mitigate floating-point numerical errors for very-low corner frequency low-pass filter with DSP
I'm designing a low-pass filter for a digital signal processing application that ideally just passes a very small bandwidth above DC. I'm using an IIR biquad filter for this, where the coefficients ...
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1answer
40 views
What is the purpose of the recurrence relation in low and high pass (audio) filters?
Newbie here. I'm familiar with time and frequency domains from math. I think I understand what low and high pass filters do, sonically. But digging into an implementation of ...
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1answer
48 views
Why does Pre-warping work with a notch filter but not a low pass filter?
Hey guys a little bit of a continuation from a previous post I made here, I found the solution as why the pre-warping was not working at the time,
However I was just playing around and found out pre ...
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1answer
134 views
IIR filter relationship between number of poles, order and second order sections
I have ported Iowa Hills Code Kit to a mcu to calculate IIR filter coefficients. They are used to initialize the CMSIS Biquad Cascade IIR Filters Using a Direct Form II Transposed Structure.
Trying to ...
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2answers
441 views
Are IIR filters (and specifically Butterworth filter) causal?
I am new to signal processing. I am learning now about filtering and I am trying to implement high pass filter (HPF),and later band-pass filter (BPF). I implement the filters in ...
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1answer
63 views
What is the best way(In terms of speed) to implement a direct form type 2 IIR Filter in VHDL?
I am trying to implement a 4th order direct form type II IIR filter in VHDL(Specifically, in xilinx FPGA) and when i implement it i get correct output yet very low maximum clock rate(Around 80 Mhz).
...
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0answers
31 views
IIR bandpass filter with very low corner frequencies
I'm trying to get in the MATLAB Signal Processing Toolbox a bandpass IIR filter having the following specifications: pass-band [0.1-0.5] Hz and stop-band attenuation 30 dB. I'm using the following ...
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2answers
86 views
Question about ideal filters
Following shows the discrete time Fourier transform of an ideal low pass filter with cutoff frequency $\omega_c$:
$$H\left(e^{j\omega}\right) =
\begin{cases}
1, & \text{if $|\omega| \le \omega_c$...
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2answers
301 views
Notch filter: differences between IIR and FIR filters
I'm trying to understand this great answer from Matt L. . It's said that "One advantage of IIR filters is that steep filters with high stopband attenuation can be realized with much fewer ...
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2answers
981 views
How do software equalizers work?
Recently, I have been studying IIR and FIR filters, and trying to create a parametric equalizer using a microcontroller. More specifically, I use the ADC on it to sample the audio at about 44 kHz, and ...
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1answer
129 views
Frequency conversion in IIR lowpass-to-lowpass transformation
We use
$\ z^{-1} \xrightarrow{} \frac{z^{-1}-\alpha}{1-{\alpha}z^{-1}}$
and
$ \alpha = \frac{\sin(\omega_c^{'}-\omega_c)/2}{\sin(\omega_c^{'}+\omega_c)/2}$
for a lowpass-to-lowpass frequency ...
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1answer
61 views
Calculation of gain at certain frequency in case of nth order IIR filter
There is this method for to set 0dB gain to be at wanted frequency (fc) (Octave/Matlab example for biquad LPF):
...
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1answer
78 views
Highpass filter square wave
Generated a 1kHz square wave in Audacity and normalized it to 0dB (fs = 44100Hz):
Added a 24dB/oct high pass filter (std Audacity plug-in), cutoff frequency set to 100Hz. Result:
Zoomed version:
...
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1answer
75 views
3 dB bandwidth of a filter
I am solving one of the question from signal processing about calculating the 3dB bandwidth of the filter. But I am stuck once I got the magnitude response of the filter. Can someone help me with this?...
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1answer
121 views
Stop band ripple vs stop band attenuation
What is difference between stop band ripple and stop band attenuation in context of filters?
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2answers
249 views
Resources for learning about filters from scratch?
Topic of filters is very important in signal processing
So i want to learn about filters from scratch and then eventually reaching FIR and IIR filters
I have some idea about low pass,high pass,band ...
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0answers
43 views
what rule has coefficients to follow for an IIR filter to be stable? [duplicate]
I'd like to play with IIR filters, but not by designing them with algorithm but rather play with the coefficients directly.
i got a stability problem though, because of course IIR filters are ...
0
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1answer
121 views
Calculating IIR Filter gain at given frequency
Let's consider an IIR filter with transfer function: $H(z)$.
Given the sampling frequency $F_s$ how can I calculate gain at say $F$ ?
When I was dealing with analog systems when I wanted to calculate ...
0
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1answer
40 views
Direct form 1 filter equation for a biquad filter
In general, we all know that the direct form 1 equation for a biquad filter is given by
$$y(n) = b_0x(n) + b_1x(n-1) + b_2x(n-2) - a_1y(n-1) - a_2y(n-2)$$
But when it comes to practical applications ...
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2answers
442 views
3 dB cut-off frequency of first-order IIR high-pass filter
As descipbed in this great answer (thank you Matt L.), the suggested exact formula was very precise.
I need a first order high-pass with similar precision.
EDIT: (clarification)
The low-pass filter ...
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1answer
38 views
changing filtering “speed” (cutoff frequency) of an IIR filter knowing only its coefficients
i got an IIR filter bu I have only the coefficients.
now i'd like to be able to change the filter characteristics of the low pass filter (the "cutoff" frequency) but all i got are a and b ...
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2answers
169 views
Coefficient Scaling of IIR filter to obtain unity gain response
I am designing a 2nd order IIR digital filter :
My tf equation with coefficients is
...
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1answer
235 views
How to apply band-pass filter and get the filtered back from frequency to time domain in python?
I know this is basic for signal processing, but, I am not sure what is wrong about my approach. I have a signal that behaves as damped sine signal with a sampling frequency of 5076Hz and 15,000 number ...
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1answer
80 views
calculate fft convolution for an LTI system given its input (in time domain) and its poles and zeros
I have considered taking the fft (MatLab) of the input (x) and create frequency bins for the first half (problems with an odd number of samples, tried solution zero paddings) and evaluate the transfer ...
2
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1answer
91 views
How to improve accuracy while converting floating point coefficients to fixed point in the case of an all pole IIR filter
I am having an all pole IIR filter of order 5 with floating point filter coefficients
...
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3answers
118 views
Is there a simpler way to calculate the amplitude response of the following filter
I would like to calculate the amplitude response $|H(z)|$, $z=e^{j\omega}$, of the following filter:
$$H(z)=\frac{\frac{b}{2}+z^{-2}}{2+bz^{-2}}$$
and I would like to avoid using Euler's formula and ...
0
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2answers
176 views
Calculating the true values of biquad filter coefficients from normalized form
I have a C code in which the IIR filter(BiQuad) uses only 4 (normalized) coefficients per stage (a2/a0,a1/a0,b2/b0,b1/b0) instead of 6 coefficients (a0,a1,a2,b0,b1,b2). I know that the value of a0 is ...
