In signal processing, a filter is a device or process that transforms a signal by selectively choosing specific frequencies and leaving others with appropriate gain or as it is.

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Forward and backward filtering

I have an input sequence $x(n)$ and impulse sequence \begin{equation} h(n) = \begin{cases} 0 & \quad \text{when } n = 0 \\ .239052 & \quad \text{when } n = 1 \\1.3357\exp(-0.650286n) & ...
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Python bandpass filter - singular matrix error

I've been trying to design a bandpass filter using scipy but I keep getting a LinAlg Singular Matrix error. I read that a singular matrix is one that is not invertable, but I'm not sure how that error ...
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72 views

Check if a filter is IIR or FIR

I have the following equation: $$H(z) = \frac{z^3+5z^2+3z+1}{10z^3}$$ I want to find out whether if its IIR or FIR. Here is the steps I have gone so far: $$H(z) = ...
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applying single pole filter to simple signal

How to apply single pole filter to simple signal fs = 500; ts = 1/fs; t = 0:ts:1-ts; fc = 50; S = cos(2*pi*fc*t);
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Correlation of an image in the Fourier Domain

I have been reading up on correlation in the frequency domain, and I just had two questions which I could not find in the book I was reading nor online: [1] So correlation is the same as a normalized ...
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101 views

FIR filters always linear?

Are Finite Impulse Response filters always linear? I looked at https://en.wikipedia.org/wiki/Nonlinear_filter and its says that if a filter does not obey linearity, it is non-linear filter. Thats ...
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45 views

What is Single pole filter?

Can anybody tell me why do we use single pole filter? And may be an example of Single pole filter in matlab. Good literature recommendations are also welcomed.Moreover, that would be good if anyone ...
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Advantage of using FIR Polyphase Decimator over just computing FIR output every D samples

Let's say you want to implement an FIR filter $h[k]$ with $L$ taps and downsample the output: $v[k] = x[k] * h[k]$ $y[m] = v[kD]$ The "naive" way would be to compute all the samples of $v[k]$, then ...
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How to test digital filters?

First the question(s): How should I write unit tests for a digital filter (band-pass/band-stop) in software? What should I be testing? Is there any sort of canonical test suite for filtering? ...
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How can you test Gamma in ISP for test?

In CMOS image sensor, there are gamma processing block in the so many ISP chains. Is there any one know how to test the gamma block only whether working good or something wrong? How can you test ? Is ...
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Image Filter Class Hierarchy [closed]

I need to create a hierarchy of Image Filter classes in C++. Do you have any ideas how to make the hierarchy and where to find source code?
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47 views

Estimating an image filter from examples

I am sure this question must be fairly easy and could have been answered on this site but perhaps I am not finding the right keywords to search for it. I would like to know what are the common ...
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61 views

Computation Costs of Filters

Is there any general knowledge regarding the costs of computation time (computation complexity) of filters? Like what types are "generally" less/more costly than others.
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Filtering with filters without even or odd symmetry in the fourier domain

I am doing a project where I have to use the fourier domain for convolution. I have been reading Digital Image processing by Rafael Gonzalez but I unsure about one thing, and I could not find anything ...
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80 views

why the ultasound image is noisy by speckle noise?

My first question : I want to know why an image is noisy ?. why the ultrasound, SAR and Laser... images are noisy by a multiplicative noise not an additive noise? Another question : So the ...
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40 views

Lag in financial trading vs Group Delay in signal processing

I'm a newbie to Signal Processing - and so I'm providing a "background" and a "question" section separately. Background: Suppose I have a linear filter (w.r.t. given as $\theta_{t+1} = \theta_t ...
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19 views

Calculating poles/zeros from 4+ order transfer function

I need to calculate the poles and zeros from minimum 4th order (max ~20) filter coefficients. I have limitations that prohibit the companion matrix/eigen decomposition method used by roots() in ...
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18 views

Reversible QIM For watermarking

I have read your paper with title "Nested Quantization IndexModulation for Reversible Watermarking and Its Application to Healthcare Information Management Systems". enter link description here ...
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58 views

What are the alternatives to FFT for computing high-resolution tone power levels?

I have a system where there's a transceiver which transmits tones on specific frequencies (about 260kHz) and a receiver which is supposed to recognize those tones. The transmitted tones are of low ...
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How to generate realistic echo to sounds?

I guess the most straightforward way of adding an artificial echo to a sound signal is to add its time-delayed version to the original signal. However, I am not sure how realistic that would sound ...
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How to filter signals with non-uniform sampling rate?

I have a digital signal that was made from analog one by staggering sampling rate: $\tau_i = \begin{cases}\tau_{even}& \text{if } i = 2n\\ \tau_{odd} & \text{if } i = 2n+1\end{cases}$ And I ...
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Use the line function commend matlab of PDE toolbox in image processing

I want to use the line new command of PDE toolbox as Matlab R2015a to restore a noisy image with gaussian noise. The PDE is : \begin{eqnarray} \nabla.(\frac{ \nabla u}{\sqrt{1+|\nabla u|^2}}) ...
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Cancelling the acoustic echo that occurs with a variable delay and volume

I am trying to build a software that records audio to a server and then broadcasts that audio into the same room that the microphone is present. This means that the audio signal is uploaded to the ...
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21 views

Treating the measured frequency response of a system as a DFT

I have frequency response data of an analog system that I would like to turn into a digital filter in Matlab. Is it kosher to think of my frequency samples as constituting a DFT of the system impulse ...
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31 views

Fir filter not working according to frequency response

I have designed a FIR filter with following parameters fs=30, f_pass1 = 1, stop1 = 0.5, f_pass2 = 3, f_stop2 = 4, A_pass = 1,A_stop = 40 Here is code : ...
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Difference between Sparse filters and Multiplier filters

I googled this differences but i haven't get any exact resources about this.Some papers said Sparse FIR filters, others Multipliers FIR filters.But no one said whether this is same or not. So my ...
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How to normalize predesigned IIR filter coefficients to have unity gain?

There is a low pass filter with difference equation already provided. $$ y_n = (x_n - 2x_{n-6} + x_{n-12}) - (-2y_{n-1} + y_{n-2}) $$ $$ a_0 = 1, a_1 = -2, a_2 = 1 $$ $$ b_0 = 1, b_6 = -2, b_{12} = ...
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37 views

noise remains after applying median filter

So I'm apply the median filter to an image, but at the output, there's blue semi-dots appearing. What are they? This is the output And the python code for anyone interested ...
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29 views

Bandwidth of time-varying harmonics of speech

For speech signals, do the harmonics have a constant bandwidth above some threshold (arbitrarily, -6 dB dropoffs)? Or does this bandwidth decrease with the upper harmonics? If this is not known, how ...
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Hilbert Transform, filters - two different phase graphs

Relationship between magnitude response and phase response for minimum phase is: Phase plots are obtained from Hilbert transform of real magnitude values. Input to Hilbert transform was a vector ...
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23 views

Understand the assumption of the ideal bright line in this paper

hope I ask my question on the right place. I am a student and my favorit subject is computer vision. I try to understand some apects of the paper "Three-dimensional multi-scale line filter for ...
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71 views

derivative filter transfer function

In many of the papers it is said that the derivative filter transfer function is given by: $$H(z) = \dfrac{1}{8T}\left(-z^{-2} - 2z^{-1} + 2z + z^{2}\right)$$ But no one gave the detailed information ...
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EM algorithm and Kalman filter

I am new to the subject of Kalman filtering and therefore my question might seem trivial. I see that there is a tight connection between Kalman filter and EM algorithm when one wants to predict the ...
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For linear IIR digital filter, what happens for negative frequencies?

By negative frequency, I refer to Fourier transform. Often, the frequency response of a digital filter is only displayed for positive frequencies. For a linear IIR digital filter, what happens for ...
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Filters - Hilbert Transform and Absolute Value of Magnitude Response

Following relationship between magnitude response and phase response for minimum phase: I have implemented in C++ code using the Hilbert Transform C code from file found online ht.c. However, I am ...
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Hilbert Transform - C or C++ code implementation

For a minimum phase system relationship of magnitude response to phase response is: In the search for C code implementation I have found a ht.c file on www.physionet.org. However, this code ...
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ITU-R 2k filter implementation

How to generate the coefficients of an itu-r 2k filter when all I know is my 0 dB point is at 2 kHz and my maximum of 6 dB is at 7 kHz
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Visualisation of bandwith of filter with sampling

I'm having some trouble visualising (and understanding) the filtering of a sampled signal. If I understand correctly, after sampling a signal, it is desired to have it go through a lowpass to ...
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67 views

Raised-Cosine Filter - phase response graphs for three kinds of filter

In the previous post it has been mentioned that the phase response of Raised-Cosine filter is linear and is given with ϕ(ω)=−ωT, where T is the delay. But, I have also read in literature that it is ...
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What is pulse train filter?

I have recently seen some code written in modelling tool like Simulink, ASCET which uses PT1 filter? Why do we use a pulse train filter? What is the difference between FIR, IIR, Chebyschev, ...
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Raised-Cosine Filter - calculating magnitude response

Here is the formula to compute magnitude of a raised-cosine filter: I know that 0 <= Beta <= 1. I am not sure what are the values for f (frequency) and Ts. I assume that some normalization ...
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Filter implementation and alternatives

I'm learning of digital filters and found a question asking why a filter with a impulse response $$h[n]= \begin{cases} \frac{1}{n^2+3n+2} & n\geq 0 \\ 0 & n<0 \\ ...
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Raised-Cosine Filter - calculating phase response

I want to compute phase response of an raised-cosine FIR filter. I have trouble finding the complex transfer function of the filter in literature (there is a real valued transfer function of ...
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138 views

IIR Filter - calculating the phase response

Using formulae from Audio EQ Cookbook from here it was easy to implement biquad IIR filters in C++, i.e. to calculate coefficients b0, b1, b2, a0, a1, a2. Now, I want to calculate the phase response ...
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31 views

SDR Signal processing - noise filtering

I'm looking for an advice with noise filtering using digital singal processing. I've been pointed here in my original question posted on Stack Overflow. So whats the problem: 1. I am using my SDR ...
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57 views

Frequency filtering with a DFT and meaning of removing complex conjugates

I've seen many implementations to filter out frequency components of some time domain signal by performing a DFT, zeroing the unwanted frequency bins, and performing the IDFT to get the filtered ...
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Finding filaments in high dimensional space

I have unit vectors in a high-dimensional space (~300) that are non-uniformly distributed over this hypersphere. There is physical meaning when the vectors are clustered together, but I'm ...
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How are filters for polyphase decimation like?

I know in naive decimation the signal should filtered by a low-pass filter with cutoff frequency equals to Nyquist rate.I don't know how the filter banks like for polyphase decimation. Are them still ...
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Removing a non linear noise trend from data

I have a dataset that looks as follows Now, this is from an actual measurement (of the reflection coefficient of a microchip with four LC resonators connected in a periodic fashion) so there is ...
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Possible to implement simple IIR filter with greater than 6 db/octave slope?

I am using the following IIR code as a low-pass filter in a software project, and it works great. However, I would like the slope of the filter to be much steeper as the one here seems to be very ...