Questions tagged [infinite-impulse-response]
Infinite impulse response (IIR) is a property of signal processing systems.
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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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1answer
37 views
IIR filter with circular buffer - Arduino
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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2answers
107 views
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 ...
2
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1answer
60 views
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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3answers
102 views
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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0answers
21 views
Impulse response of discrete time system
I am learning about discrete systems and in this derivation something struck me as quite odd. Solving for $A_0$ in this equation seems dubious as it ignored all other values of $n$. For example, at $n=...
6
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3answers
300 views
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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1answer
64 views
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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1answer
98 views
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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1answer
158 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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2answers
47 views
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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0answers
71 views
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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3answers
377 views
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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0answers
22 views
Constructing a lowpass digital differentiator such that maximum error is $n$ dB for passband
I want to construct a lowpass digital differentiator with uniform-interval samples such that error from ideal differentiator is $n$ dB in magnitude at maximum for the passband up to frequency $\...
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1answer
53 views
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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1answer
68 views
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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2answers
65 views
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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1answer
293 views
FIR butterworth also possible or just IIR?
can we use butterworth and other such filters like chebyshev,elliptic etc with FIR
or they can be only used with IIR?
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1answer
100 views
How to apply two notch filters simultaneously
I have a sound file that I need to apply a notch filter to in Matlab.
comparing to original file I have two frequencies which are the noise. Applying a notch filter like this one:
...
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0answers
78 views
Phase noise modeling using gnuradio IIR filter
I need some advice regarding phase noise modeling using gnuradio IIR filter. I'm trying to synthesize phase noise (multiplicative) with a given noise mask. In one paper, the authors were able to ...
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1answer
37 views
difference between conventional analog butterworth filter and that implemented through IIR
I am confused what is difference between conventional analog butterworth filter and that implemented through digital technique using IIR
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1answer
88 views
Design of FIR and IIR filters in Matlab
I need to create 4 different pass-band filters. What remains the same throughout is the following:
Sampling Frequency = $3000Hz$
Pass-band Frequency = $900Hz-1200Hz$
Now, these are the filters I ...
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1answer
695 views
Single-pole IIR low-pass filter - which is the correct formula for the decay coefficient?
A single-pole IIR low-pass filter can be defined in discrete time as y += a * (x - y), where y is the output sample, ...
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1answer
325 views
What is zero-phase filtering and forward-backward filtering?
I am pretty familiar with IIR and FIR filtering and I have implemented them in my several projects. However, recently i found something called zero phase filtering. I have tried to understand it but ...
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1answer
84 views
Orders of complimentary butterworth filters for IMU
I'm currently trying to design a complimentary filter for deployment on a drone, as part of an assessed semester project. Even though processing power is not an issue (we have GHz, lots of pipelining ...
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3answers
73 views
Why using the impulse respond of an LTI to characterize its output?
We all know that every LTI, is defined by its transfer function, so we can determine the output of any system, (using common transforms). It is also known that we can determine the output of any LTI ...
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1answer
33 views
How do I add more resolution / taps to an analog -> digital filter?
(I am trying to create an IIR audio filter that adds reverb to an initial sample)
Say I designed an analog filter to model acoustic attenuation based on the following mathematical model:
$$
I = I_0 ...
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1answer
81 views
mpiir_l2(): Results are not IIR but FIR filters - why and how to avoid this?
I'm using mpiir_l2() from user Matt L's PhD thesis to design IIR filters. I set the number of numerator and denominator coefficients both to the same value (between ...
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2answers
328 views
IIR high pass filter
I'm trying implement an IIR filter. I know the IIR filter come from that equation:
and i found that for high pass filter the coefficients are:
where fc = cut freq.
here my matlab code:
...
1
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1answer
62 views
iir biquad filter not working
I am trying to implement a butterworth bandpass filter
My filter requirement is Fs= 500Hz, Fc1=0.4Hz, Fc2=4Hz, Oreder=2.
Below is the code which is implemented on 16bit-mcu and is called for every ...
4
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2answers
116 views
references for techniques to reduce recursive filter startup transients
I am trying to track down references (published articles or reports ideally) that establish the basis for some of the techniques being used to minimize the effect of recursive digital filter startup ...
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1answer
83 views
VHDL fixed point implementation of IIR filter
I have a filter described by the following transfer function H(z):
$$H(z) = \frac{156 - 156z^{-2}}{16384 - 32443z^{-1}+16073z^{-2}}$$
How will this be implemented with the first term in the ...
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1answer
147 views
How to find the impulse response of this system with complex roots?
I've been working trying to analyze a causal stable system. Hopefully a numeric example such as the one I am working on, and the problems I face during it could be useful to others.
I have this ...
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2answers
153 views
How to compare many bandpass filters (for their signal propogation delay)?
Let's say we have an audio signal sampled at 96 kHz, and we want to compare several bandpass filters to find the one with the lowest rectangular-envelope-propagation-delay (see graph below).
The band ...
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1answer
56 views
How does an IIR system affect magnitude and phase of a sinusoidal signal
Consider an IIR system with impulse response $h[n]=\left( \frac{1}{\sqrt{3}} \right)^n u[n]$. If I apply $x[n]=\cos(n \frac{\pi}{2} + \varphi)$ at the input, how can I determine the change in ...
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2answers
60 views
How can I convert a step response that is described by the sum of two exponents to an IIR filter analytically?
If a system has the following step response:
$$\begin{align}
y(t) &= 1 - \Big(A e^{−t/T_1} + (1-A) e^{−t/T_2}\Big) \\
&= 1 - A e^{−t/T_1} - (1-A) e^{−t/T_2} \\
\end{align}$$
and I know the ...
6
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4answers
1k views
Why is the first value in digital first-order IIR filter impulse response not the largest?
When I create a digital first-order IIR low-pass filter with scipy (code below), I get the following coefficients:
B: [ 0.1367 0.1367]
A: [ 1. -0.7265]
The ...
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2answers
81 views
Calculating a NRR of an IIR
I'd like to calculate the Noise Reduction Ratio of a system.
The system I have is $$ H(z)= \frac{z^{-5}}{1-0.1z^-1}.$$
For FIR Filters this can easily done by $$ \sum h[n].$$
For an IIR Filter this ...
5
votes
1answer
161 views
Advancing a causal IIR filter's impulse response
Given an infinite impulse response (IIR) filter as coefficients in a topology of your choice, what is a straightforward way to modify the filter so that the impulse response is shifted in time (...
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1answer
59 views
Simple question about Sinc()
Suppose I use the ideal lowpass filter eq to attempt creating a IIR filter using it
:
$$
h[n] = \frac{\sin(\omega_c \, n)}{\pi \, n}, \qquad -\infty < n < \infty
$$
Obviously, I can't really (...
5
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6answers
280 views
Optimal $ n $ -th Order IIR /AR Approximation of a Moving Average Filter
I would like to approximate a moving average filter with an IIR filter of much lower order than the tap-length of the moving average filter. Optimality shall refer to the $L_2$ norm of the impulse ...
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votes
1answer
57 views
Design digital filter with model order reduction (MOR) and other methods
IIR filters can be designed using different methods,such as:
Analog Prototyping
Direct Design
Generalized Butterworth Design
Parametric Modeling
https://www.mathworks.com/help/signal/ug/iir-filter-...
3
votes
1answer
88 views
How would I calculate the state-variables of digital biquad filter (direct form II transposed) at steady-state?
I'm attempting to calculate the steady-state state variables for a digital biquad filter direct form II (transposed). Illustration
For example, let assume the filter is fed a constant input of ...
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2answers
78 views
How do you initialize the output of a second-order-section filter?
I've got a 4 stage second-order-section filter. When I turn this filter on, it assumes it is starting from zero and takes forever to converge on the actual signal.
For example, let's say I have a ...
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1answer
83 views
Question of Digital filter; stability and order
Below 1~6 are my question.
Shortcomings of IIR filter.
Mean of unstable. (Things that will happen when system is unstable.)
How to select the best order(n).
What happens when I raise order too much.
...
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1answer
261 views
IIR filter design fitting step response
I have access to the step response of a system and I want to find its poles and zeros without knowing the order of the system.
Consider an example of a step response of the system shown in the ...
1
vote
1answer
118 views
Do you recognize this filter?
I'm trying to decipher the uncommented source code of SoundBox which is a little music tracker written in javascript.
There is an included synthesizer, which applies a filter on the output samples. I'...
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0answers
111 views
IIR (non linear phase) filters
As you know, a nonlinear phase filter (in passband), distorts the frequency contents of passband region of signal. In general, Why do we use such filters in the case they cause distortion in the ...
2
votes
1answer
57 views
Find a stable transfer function $G(z)$ such that $|G(z)| = |H(z)|$
Consider the following causal IIR transfer function:
$$ H(z) = \frac{2z^3 - 4z^2 + 9}{(z-3)(z^2+z+0.5)} $$
Is $H(z)$ a stable function? If it is not stable, find a stable transfer function $G(z)...
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1answer
196 views
Applying multiple IIR and FIR filters at once
I would like to appy multiple filters to a signal at once.
Let's assume I got two frequency bands I want to extract. I compute a Butterworth Filter for 300-500Hz and one for 700-800Hz. I would like to ...
