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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How to caclulate local gradient of image

I have a question about local gradient. I know that gradient function is support by matlab. But for the local gradient, it does not support. Do you know how to calcualte local gradient of a given ...
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1answer
26 views

Speaker Recognition

How can you filter out a person's voice from a group of people talking? We have a sample of each person's voice from the group, and the sample of the entire group talking at once. Both samples are ...
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9 views

How can I calculate the Gaussian range and space parameters in a bilateral filter?

Let's suppose I have the following [4x10] image: 1 3 4 5 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 5 3 5 6 8 9 0 0 2 3 4 6 7 8 9 0 8 9 How can I calculate its space ...
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2answers
40 views

Extra energy when altering frequency amplitudes

How can I convert a time signal (audio) into the frequency domain, multiply frequency amplitudes by a vector of scalars, and convert it back into the time domain, without messing up timing information ...
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1answer
60 views

Differential Equation of a Band Pass Filter

I'm struggling with a signal analysis electrical engineering college assignment. We need to a derive differential equation for a low-pass filter, high-pass filter and a band pass filter (made by ...
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1answer
39 views

Savitzky-Golay filter parameters

I am trying to smooth a series of data in order to obtain a continuous function that could represent that given data set. It came out that the Savitzky-Golay method could be a good way. Now, I don't ...
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1answer
40 views

Amplitude Spectrum, Nyquist Frequency, mixed/min/max wavelets

The problem is here. Now I know the definition of mixed/max/min phase wavelets, whether the roots lie within the unit circle or not. Starting from n = 1, let $$ x_t = ( 5, 6) $$ $$ X(z) = 5 + 6z $$ ...
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2answers
57 views

Difference between band pass vs. low pass + high pass?

I am reading a paper in which they filter EEG signal using a notch filter to remove the power supply component of 50 Hz, then a high pass filter at 0.3 Hz to remove artifacts resulting from breathing, ...
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33 views

IIR filter SOS and Direct Forms doubt

I have below doubts, so confusing! As I don't want to assume from what I read, I am asking for help here! Are Second Order Sections another name for biQuads ? If I have 2 single pole transfer ...
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26 views

Digital Filter for FRDMKL25Z

I was wondering if I can get some comments for my filter design. Signal to Filter: F(x)=sin(2*pi*80*t)+sin(2*pi*125*t) Since I'm implementing this in C for an embedded system I have chosen and IIR ...
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1answer
34 views

Given input and output time series, obtaining filter design

Say I have 5 minutes of input and output audio. One method I know is to do FFT on windows from input and output. Then divide FFT output into bins and find average energy in various bands for all the ...
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1answer
55 views

Fir filter confusion

I am learning about fir filter and i'm confused. I tried googling about it and it becamse worse. I am trying to find out different types of fir filter. 1. Is direct form and n-tap fir filter the same? ...
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1answer
42 views

Continuous-time mathematical formula for deconvolution filters

I have an elementary function $p:\mathbb{R}^2\rightarrow\mathbb{R}$ which (locally) represents an image. It's a polynomial, and its the result of the following 2D convolution: $$p=f\star G\star ...
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29 views

Help implementing biquad iir filters

i have a matlab simulink model, which consist of three blocks From Wav file two IIR filter block Save to wave file IIR filter transfer function is ...
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2answers
393 views

What is the math behind median filter's noise reduction property?

I am interested in understanding the mathematical reason for why does applying a median filter on an image (or signal) result in reduction of noise.
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3answers
78 views

Which filters are the most commonly used and easier to implement for ECG noise removal?

ECG signal is affected by interferences such as the Powerline Interference, Baseline Wandering and Muscle Noise. There are many filters available which can reasonably cancel these types of noise. ...
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1answer
72 views

How to make filters?

I am trying to make filters like sepia filter in my app like other photo editing applications , till now I don't have any idea about it , Can any one help me out ...
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2answers
62 views

Approximate the magnitude response of an analog filter with a digital filter, starting from its gain expression

I have an analog filter with its frequency response curve in dB described by the following expression: $$ N_{dB}=20log_{10}\omega t_1 \sqrt{\frac{1+(\omega t_2)^2}{1+(\omega t_1)^2}} $$ This ...
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98 views

Malaysia Flight 370 Image Processing

I wish that all those people on that flight were with us, and maybe they still are, as I like to think they are on an island somewhere waiting to us to find them ... however, it does not look good... ...
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1answer
53 views

Removing empty/low amplitude part from signal

I have a signal of length 'N' which looks like this ...
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0answers
49 views

Why does the inverse fourier transform of a lowpass filter have complex components in matlab?

I am quite confused whether the following numerical differences i find are just severe round off errors made by matlab, or something i am doing wrong. The following happened when trying to see what a ...
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0answers
15 views

Meaning of tight frame in the context of texture synthesis

I am currently reading "A parametric texture model based on joint statistics of complex wavelet coefficients", by Portilla and Simoncelli. In this article, they use the "steerable pyramid" to ...
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0answers
39 views

Common mode rejection (in software) without a reference channel? EEG data

Summary I need to remove artifact that appears strongly on all channels in my EEG data. It's already recorded (from another lab) so I can't use hardware solutions. Also: band overlap and no reference ...
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2answers
75 views

Extracting phase using Goertzel filter in Python

I'm investigating whether it's practical to use a Goertzel filter to decipher a binary message phase-shift encoded into a single frequency. Here is my result: I would like the bottom line to ...
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1answer
43 views

How to implement a filter in matlab

I want to implement the 'filter' function in matlab but I just can't seem to replicate the results I get when using the matlab function. My understanding of the matlab function is that it takes 3 ...
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2answers
212 views

Trivial echo separation

Say we have a signal S, and we composite it with a 0.1-volume 30-sample-delayed version of itself, so: T(k) = S(k) + 0.1*S(k-30) How would one rearrange this ...
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1answer
307 views

Upsample data using FFTs. How is this exactly done?

I am basing my question on this post here, because I would like additional details on it, as I have not had any success in re-creating it. I would like to simply learn, in no uncertain terms, how to ...
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1answer
63 views

Which kernel produces sharper image

kernel A = [ 0 -1 0 -1 4 -1 0 -1 0 ] and B = [-1 0 -1 0 4 0 -1 0 -1 ] i have found the frequency spectrums with ...
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1answer
58 views

Is there a closed form expression for main-lobe width increase given a window?

We know that when we window a signal, we increase the main-lobe width. Let 'main-lobe-width' here be the null-to-null bandwidth of the main lobe. Let us further more say that the main-lobe width of a ...
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3answers
69 views

Connection between filter equation in frequency domain and difference equation in time domain?

I know that the frequency response of a filter is described by equation: H(w) = 1-1.176*e^(-jw) + e^(-j2w) , where w is the angular frequency. Then in time domain ...
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1answer
36 views

Q value for a high pass filter

How to calculate the Q value for a high pass filter ? Ps: I'm a beginner in signal processing, so please put it in simple terms.
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1answer
63 views

Analogous filter to Kalman that maximizes mode (as opposed to minimizing variance)

I may have a potential application where maximizing the mode (as opposed to typically minimizing the variance) would be useful for state estimates. The situation may arise from skewed distributions ...
2
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1answer
64 views

Is it possible to open up this particular convolution equation?

I have three vectors, $x[n]$, $w[n]$, and $z[n]$. I need to compute: $y[n] = z[n] * \Big(x[n] \cdot w[n] \Big)$. This is easy to do. However, is there a way I can do this by 'opening' up the ...
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1answer
60 views

What is the difference between Filters and Windowing?

I'm finding some difficulties to understand the difference between Filters, and Windowing. accoriding to my understanding both filters and window functions will make changes to the input signal ...
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1answer
86 views

Anisotropic diffusion

I am working with speckle noise reduction in ultrasound images. At present I am learning about anisotropic diffusion.I will explain first what I have understood about anisotropic diffusion. I learnt ...
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1answer
76 views

How can I detect if a filter is FIR or IIR according to impulse response graph?

I have the following two graphs but I don't know how to recognize from the graph if they are IIR or FIR! Can you please guide me through? P.S.: Does MATLAB have a function to detect if an impulse ...
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1answer
58 views

Filtering a signal to have a constant exponential moving average

Problem I wish to filter a discrete-time input signal, $x[n]$, so as the output signal's, $y[n]$, exponential moving average, $a[n+1] = a[n] + \alpha(y[n] - a[n])$, tracks around a constant reference ...
3
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1answer
72 views

Correction of a signal through a transmitter

I am inquiring as to a practical way to solve a problem I have. Basically, I need to transmit a signal, $x[n]$, through a seismic transmitter. (It will go through a D/A, etc). The transmitter that ...
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1answer
72 views

DC component of a discrete filter

I know that many books and papers talk about the DC offset/DC component of a filter. How do we define the DC offset mathematically, for the case of discrete filters?
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1answer
147 views

What does fir1 in matlab does?

May i know what does this function do in matlab? num = fir1(80, [5Hz, 50Hz]); I know that 5 Hz is the low cut-off freq and 50 Hz is the high cut-off freq. I'm ...
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3answers
94 views

Mixed time/frequency domain data

I'm afraid this might be a bit of an elementary question, but I'm afraid I'm a little new to this. I've got a system that measures a frequency spectrum to find resonant frequencies. It does this by ...
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1answer
66 views

Do antisymmetric FIR filters preserve the shape of their input waveforms?

For antisymmetric FIR windows, the phase response is of the form $a\omega+b$, where $b$ is $\pm\frac{\pi}{2}$, so it is not strictly linear. Does the waveform of the signal gets retained?
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1answer
71 views

linear phase and generalised linear phase filters

I know that for linear phase filters, all frequency components have equal delay times. That is, there is no distortion of signal due to the time delay of frequencies relative to one another. ...
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2answers
86 views

Criteria to distinguish FIR and IIR filters from difference equation?

What criteria should be used to safely decide if it is an IIR filter or FIR filter from a difference equation? FIR filter are always stable, meaning all poles are inside the unit circle AND have ...
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7answers
232 views

Downsampling/Decimation - When is well done?

I am working on decimation of signal, and I want to know which is the best way to understand if the downsampling is well done or not. At the moment I am comparing the FFT of the source signal and the ...
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1answer
53 views

Determing the frequency of a signal with a sample at a time [closed]

How to determine the frequency of a signal with a value of the sample and value of the time instant the sample was taken ?
3
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2answers
121 views

How to use low pass filter in Matlab for discrete data? [closed]

As see in the picture, there are high frequency noise in the signal. How to design a low-pass filter to eliminate the noise? How to apply this filter in Matlab?
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2answers
90 views

Using filters on an 8 bit song has absolutely no effect after saving

This seems like such a trivial problem but there is no answer anywhere. I'm trying to convert a 16bit song to 8bit so I can play it with a microcontroller. This creates a lot of noise. Every time I ...
3
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2answers
68 views

Ways to compute the n-the derivative of a discrete signal

This is a pretty general question about how to compute derivatives of a digital signal $x[n]$. I would like to know what are the different approaches (from naive to complex) and how are they compared ...
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36 views

How can I apply a Gabor filter to a sine waveform?

I am an ECE student, and I am doing my project on underwater communication. The main concept of my project is to denoise the signal by using UFB and WPD algorithms, and giving that output to a ...