Questions tagged [filters]

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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29 views

Harmonic Product Spectrum from FFT output to the fundamental frequency

I'm trying to do the HPS algorithm on my FFT output, but I'm stuck here. My signal is from a bass (cable), 16bits, 48.000Hz. I split in time domain the array of the whole record into multiple arrays ...
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How do Anti-Aliasing Filters filter the signal?

I have programmed a anti-aliasing filter that uses the fourier-transformation and makes a perfect cutoff on my desired cutoff frequency for downsampling without aliasing. I have read about other ...
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1answer
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Why does my signal magnitude increase after adaptive filtering?

I am using a series-cascade of multiple NLMS adaptive filters each with step size 0.0040, leakage factor 1.0, and 100 filter taps. My signal gains magnitude at each step of the filtering, say the peak ...
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24 views

Do all systems in z domain are filters?

Normally a system transfer function is represented by H(z) I want to know wether all those system transfer functions are only representing a digital filter? Or their any other thing/entity in z ...
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Canceling interference (such as harmonics from out of band source )

I have a vague-ish question, if it makes sense: The desired received signal (from source S1) was carried at 3 GHz passband carrier frequency, with bandwidth 20 MHz. It was interfered with by the 3rd ...
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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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How to write Matlab code for generating orthogonal signal in time domain? [closed]

I have generated a Gaussian pulse in time domain and have passed through an FIR filter.I need to generate an orthogonal pulse in time domain . I need help to write code for that in Matlab.
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FFT looking messy after filtering process

I have a vibration signal (25.6 kHz) which has been through the following filters: ...
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22 views

Short Time Discrete Fourier Transform to detect time dependent changes in a frequency of interest & Filter

I am working in matlab to compute the fourier relative phase of two signals as per https://sci-hub.tw/10.1123/jab.2017-0250 I have identified the fundamental frequency ($f_1$) for the signals (1.7 Hz)...
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39 views

wavelength from peaks

I have a simple 1sec signal of 1Hz added with 10Hz. I can detect all peaks (I use Python Scipy find_peaks) and I'm trying to deduce the 10Hz signal from those peaks. I can do it but it's not clean ...
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How to avoid overtones in audio signal

I'm trying to make a program that catch and audio signal of a bass and show the notes that have been played. My program: Gets the sound and put it in a double data type array. (48 000Hz, 16bits) ...
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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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Exponential Moving Average Function Notation

I'am trying to define an exponential moving average function denoted $EMA_{\alpha}(x_{n})$ where $\alpha$ is the smoothing coefficient and $x_{n}$ is the input signal. My first approach was to use the ...
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What steps and methods are recommended to process various signals of a IMU sensor [closed]

I'm new here because I'm making my degree final project. See more my profile for more information. I want you to recommend me what are the tools to analyse the sampled signals and process them in ...
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How to compute the LMS DFE based equalizer FF and FB coefficients in a adaptative way?

I am still struggling to understand the filter updating process, the computation of the demodulated result and the computation of the error. Attached you can find the simulation I've done so far, the ...
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Removal of EEG noise using cascading adaptive filtering technique

I am required to filter out noise from EEG data using preferably Python or MATLAB. My dataset contains values for 64-electrode EEG along with their time-corresponding HEOG (horizontal eye movement), ...
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Unexpected Results in Rank Transform Based Disparity Estimation

I am applying a normal rank transform of size 7 x 7 to the right/left shifted images in order to obtain their disparity map using a typical block matching algorithm in MATLAB. My code to obtain to the ...
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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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Eye pattern construction and interpretation

I have read some text about the eye pattern (or eye diagram), but I do not understand how should I read it. The wikipedia definition of it is this one: In telecommunication, an eye pattern, also ...
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Can some one explain what is the meaning ( in real life) of anti causal (precursor) part of the channel taps?

The channel taps are classified into postcursor (causal) and the precursor (anti-causal) parts. \begin{equation}y_{k}=\sum_{l=-L_{2}}^{l=L_{1}} h_{l} x_{k-l}+n_{k}\end{equation} here $h_{l}$ is the $...
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I can't wrap my mind around the concept of filtering and the unit circle ? any help? [closed]

Can someone elaborate this theory where there is a link between the stability of a filter and the zeros or nulls being on the unit circle?
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35 views

Finding the amplidude of a single frequency in signal

I'm not experienced whatsoever in signal processing. I want to isolate a single frequency (83 Hz) out of a noisy signal. Goertzel works just fine but was wondering if there was any other, maybe even (...
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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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Well known waveforms or signal equations for filter testing

I'm testing a software based DSP filter. To test I'm generating some sine waves and adding them together. I'm about to start trying to generate more complicated input signals with trigonometric ...
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49 views

Detect when signal starts oscillating

I have a signal which consists of oscillations riding on square waves as shown in the image below. I wish to detect the time at which oscillatory events occur (as shown by the red star). Each square ...
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Is it useful to apply edge detection filter as a preprocessing step before applying CNN?

Background: my future boss would like me to apply a number of low level filters to industrial images before applying machine learning methods on them. From my knowledge this doesn't make any sense as ...
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Mean of input based on acf of filtered output

By looking at the ACF of the output of a filter whose impulse response I know, can I approximate the mean of the input? For example ...
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Code implementation of Channel estimation based DFE Equalizer in matlab (or octave) without the the signal processing tool box

I want to implement a DFE in matlab without the signal processing toolbox: I have two filters ( FeedForward and FeedBack) with taps length equal to 15. I know the update equation of the LMS ...
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1answer
22 views

Can someone explain me what is the doppler spectrum?

I have a signal generated in matlab, with Rayleigh Fading, how can I add a given type of Doppler spectrum ( Gaussian for instance) to that signal ? Any help will be really appreciated
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MMSE- Channel estimated based - DFE Equalization

For HF ionospheric channels ( frequency range 3 up to 30 MHz), I Want to make channel equalization in time domain, using MMSE criterion. I have to do it using the channel estimation. I have some ...
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51 views

Filter response to sinusoidal input signal

This question is related to Does 46 dB gain of a filter for a frequency imply 200 times more amplitude? In the accepted answer it is mentioned that "For a sine wave input the amplitude of the steady ...
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Obtaining a high sample rate digital approximation to an analog filter from lower frequency measurements

Consider a set of dense, but generally irregularly-spaced frequency response measurements of some real low-pass analog filter. Denote the maximum frequency for which a frequency response measurement ...
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Early-Late Symbol Synchronizer on Non-Triangular Pulses

I've been studying the basics of digital communications using the free book at desktopsdr.com. One of the examples is a 4-QAM demodulator which where symbol timing recovery is done with some Early-...
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Does 46 dB gain of a filter for a frequency imply 200 times more amplitude?

Consider we have a IIR filter or order 2 and it has gain of say 46.02 dB for frequency $f_0$. Now if we apply a time domain signal of frequency $f_0$ to the filter for a long time, can we expect to ...
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2D DFT of a filter kernel

for understanding i want to compute the DFT out of the 3x3 filter kernel using the shifting property: $$\begin{bmatrix}0& 1 & 0\\1 & 0 & 1 \\ 0 & 1 & 0\end{bmatrix} \cdot \...
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How to make low pass filter using frequency sampling method?

https://www.allaboutcircuits.com/technical-articles/design-of-fir-filters-using-frequency-sampling-method/ So there is two main equation: I wish to filter out frequency $\le 10000Hz$, for example. ...
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1answer
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Puzzled by CIC filters

I have been trying to wrap my head around CIC filters. Say that I want to do filtered decimation by a factor D. Option#1: boxcar filter. Each output sample is formed by taking the sum of D input ...
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Path delay influence in BER performance using Rayleigh channel

I am simulating a DSSS modulation in a Rayleigh channel to get the BER performance. For these purpose I am using the comm.RayleighChannel object. My problem comes when I change the Paths delays of the ...
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50 views

Reducing one frequency in song

How would I take a song input and output the same song without certain frequency ranges? Based on my research so far, the song should be broken down into chucks, FFT it, reduce the target frequency ...
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Trouble with understanding moving average filter as an oversampling filter

I am struggling with understanding how an moving average filter can increase ENOB in a given sample. I wrote a test for a simple MA (moving average) filter in matlab. The algorithm to create new MA ...
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1answer
123 views

Cascaded One-Zero Filter IR

given the one-zero digital filter, $$y[n] = x[n]\cdot \frac{1}{2} + x[n-1] \cdot \frac{1}{2}$$ Which has the transfer function: $$H(z) = (1+z^{-1})\cdot \frac{1}{2}$$ and taking $M$ of these ...
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Can a Kalman Filter Be Applied Using Measurement-Space Dependent Sensors?

I'm currently attempting to apply a Kalman filter to track the angular position, velocity, and acceleration of a bike wheel, and I'm having a lot of trouble, so I want to check if I'm even applying ...
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Calculating phase shift between two sines of equal, unknown, amplitude and frequency

I've got a source signal $s_1(t)$ and a system affecting that, yielding a phase-shifted version $s_2(t)$; \begin{align} \color{blue}{s_1(t)} &= A\sin(t+\phi_1)\\ \color{red}{s_2(t)} &= A\sin(...
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Weiner filter vs Analytical Linear optimal estimator

I've been learning recently about estimation of stochastic processes in general, and linear estimation in particular. On one hand I've seen the following estimation of $X[n]$ from $Y[n]$ - $X_{opt} ...
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Rotation matrix covariance to quaternion covariance in attitude estimation

Given a $3 \times 3$ rotation matrix $\mathbf{R}$ with an associated $3 \times 3$ covariance matrix $\mathbf{P}$ how do I compute the associated $4 \times 4$ covariance matrix $\mathbf{Q}$ of the ...
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368 views

Butterworth filter transfer function in time domain

Preliminaries I need to know the response of Butterworth filter in time domain of the following input (at least numerically): $$ x(t) = \theta(t)(1-\exp\{-at\})\exp\{-bt\}, \quad a,b>0,\quad a\gg ...
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Whitening Filter for Noise Estimation

The signal I'm working on includes some noise which is I assume Gaussian white noise with zero mean and an arbitrary variance. So, it is like; ...
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1answer
60 views

A Delay Between Two Filtered Chaotic Signals

it is a common practice to use a shift of cross-correlation peak to evaluate a group time delay of two signals (chaotic signals are included). Can one synchronously and equally filter these chaotic ...
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1answer
1k views

Who first understood the importance of poles?

Who first understood (or at least published papers on) the importance of poles in understanding transfer functions in the frequency domain? If I had to guess, I'd suggest Nyquist or Bode but I know ...
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1answer
66 views

y(t) a of an integrator circuit

I have a signal $$ x(t)= \frac{1}{T} e^{-\frac{t}{T}} u(t) - \frac{1}{T} e^{\frac{t}{T}} u(-t) $$ and I know that it transits in a integrator circuit and I have to find y(t) in time and frequency ...

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