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Questions tagged [filtering]

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43 views

Zone Plate Reconstruction

I am trying to reconstruct the Zone Plate image and am struggling to remove the last remaining aliasing. ShaderToy: https://www.shadertoy.com/view/wdGGWK In the shader above you can see that I am ...
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1answer
50 views

How to filter very low amplitude staircase signal from a background noise

I have a staircase signal of a specific pattern that is drowned in a background noise. The ratio of signal to noise amplitude is nearly $10^{-4}$. I have attached the image of both with this post. I ...
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0answers
31 views

How to downsample my data readings from 0.5hz to 0.001667hz. Do I filter and downsample?

I have a device that, in the lab, takes voltage readings every 2 seconds. However in real-life application the device would only wake every 10 minutes and then take a 100 readings whilst awake. How do ...
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1answer
93 views

How the zero - phase filter without filtered signal truncation at the end can be implemented?

I mean what for the window FIR filter the filtered signal is truncated at the end because impulse response of the filter is symmetric. For example the code from here (in python) (lowpass FIR filter) ...
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1answer
123 views

DC Spur in DAC output

I have a design in which a signal from ADC is filtered and then played by DAC. In FPGA the real signal is converted to quadrature using DDS with 70 MHz frequency. After filtering, the baseband signal ...
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1answer
91 views

Looking for a analytical formula to compute the central frequency of a signal analyzed by a discrete wavelet at a given scale

I am reading this paper by Han et al. (2014). In this article, the authors extract detailed information from geomagnetic data sampled at 1Hz using a daubechies 5 (db5) wavelet: they reconstruct the ...
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2answers
49 views

When to apply circular convolution formulas?

Context I am studying the family of Discrete Trignometric Transforms (DTT): Discrete Cosine Transforms (DCT) and Discrete Sine Transforms (DST). And trying to understanding more their properties, I ...
1
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1answer
234 views

Real-time oscillation-like noise filtering

I am making real-time measurements, which are affected by some noise. This noise has oscillating pattern, i.e. the total signal tends to oscillate around the mean value. The examples of measurements ...
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1answer
353 views

Use Scale Space Representation to Filter Single Image

Currently I hope to use scale space representation to filter one image. Features in one image can be filtered using an Gaussian smooth filter with one optimal sigma. It means different features in one ...
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2answers
1k views

Median Filter for salt and pepper noise removal

Why median filter is considered as good for removal of salt and pepper noise? What are the other filters used for the same?
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2answers
14k views

Given Position Measurements, How to Estimate Velocity and Acceleration

This is simple i thought, but my naive approach led to a very noisy result. I have this sample times and positions in a file named t_angle.txt: ...
-1
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1answer
117 views

Real time FFT & IFFT with low pass filter

I am processing the signal from MPU6050. Applying FIR filter in the frequency domain and then taking IFFT to get filtered signal but getting some spikes in the output signal. Searched a lot about it ...
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2answers
365 views

Role of the rank of the filter mask matrix in image processing?

I'm reading a material where it says that a filter mask or kernel can be separable if the matrix of the filter mask has a rank 1. The two slides which describes this are as below: Reading these ...
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1answer
38 views

Filtering in the Frequency Domain - DIP [closed]

I am trying to do some filtering with a gray scale image in the frequency domain. I am just getting into matlab after some time away from any signal processing or coding and can't quite seem to get my ...
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2answers
236 views

Easy way to get rid of noise in a hand drawing

I would like to take a user's hand drawn input, and filter out "noise", aka small sketches or blobs, where the user might have screwed up and accidentally touched his hand to the drawing device, or ...
0
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1answer
22 views

Comparisons of FIR Causal filters of type HRIR in Discrete Time and Frequency Domains

I have just implemented a Discrete Time Convolution between HRIR filter at a range of angles. I also implemented an Overlalp-and-Add method and FFT and IFFT to compute the same convolution in ...
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2answers
304 views

Anisotropic Diffusion Filter - Intuition Behind Parameters

I need to know what is iteration and divergence in anisotropic diffusion filter technique. Isotropic diffusion $$\frac{\partial I(x, y, z)}{\partial t}={\rm div}\left[c\cdot \nabla I\left(x, y, ...
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0answers
18 views

Image Processing Perspective Transform

This youtube video shows the current world record for smb1 speedrun, but it is recorded from a phone on a CRT TV. https://www.youtube.com/watch?v=IuVLtaB8uQk Is it possible through perspective ...
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2answers
68 views

How Butterworth low-pass filter can be applied on a digital signal (i.e. discrete representation of a signal)?

I would like to know how to apply a low pass filter (Butterworth) to a digital signal. So, I have some values of the signal, let's say $S(t)$. Those values are equally spaced in time. I have read the ...
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2answers
54 views

Cross-correlation of filtered random processes

I have a wide-sense-stationary (WSS) process $\{x(t)\}$ and two linear filters with impulse functions $h_1$ and $h_2$. Let $\delta(\omega)$ be the power spectrum of $\{x(t)\}$ and $$H_1:\omega\...
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1answer
113 views

Remove high resolution spurious peaks from sinusoidal signal

I have the current from a LEM transducer measured. The measurement is taken on the output of a transformer. The signal is a 50 Hz signal, measured at 100kHz. When the demand of the system is increased ...
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2answers
2k views

What is the difference between the sampling frequency of signal and sampling frequency of filter

I believe that there is no connection between the sampling frequency used for converting an analogue filter to digital filter and the one used to sample a signal that the filter will be used on. But I ...
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1answer
39 views

Adaptive Band pass filter for extracting respiratory waveform from accelerometer data

I am recording data from an accelerometer attached to the chest (1000Hz). I need to extract the respiratory waveform. I tried an adaptive bandpass filter based on a dominant frequency in my signal ...
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1answer
164 views

How to calculate the Fourier transform of a mean filter in Matlab?

In Matlab, how can I calculate the discrete-space Fourier transform of a mean which takes the average of 4 adjacent points, with this kernel $$\begin{pmatrix} 0 &1& 0\\ 1 &0&...
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2answers
1k views

MATLAB : How to filter a data signal

I have a data signal (column vector) with N values taken over at specific sample rate (dx) at a fixed frequency. After taking the Fourrier transform of this signal and representing it in the Fourier ...
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2answers
36 views

Downsides of higher order filtfilt's

I understand that with a standard filter, higher order will yield sharper frequency selection at the cost of increased phase delay. However, with so-called zero-phase-distortion filters like that ...
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0answers
41 views

Avoiding transients during filtering: Padding or Gustafsson's method?

I'm pretty uneducated when it comes to filtering, more of a stats guy, but I have to bandpass some signals and after a bunch of reading today I understand that the ...
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1answer
38 views

How to sketch this multirate system spectrum?

In the following system: The signal x(n) is upsampled by 2 and then filtered. The signal and the filter have the following spectrum: After upsampling the spectrum of X would look the same except ...
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0answers
61 views

Polyphase resampling delay

I want to implement polyphase resampling. For this, I wrote a script in matlab. The script performs the following sequence of actions: ...
0
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1answer
113 views

Manual filter or digital filter first for EEG?

I am getting conflicting advise regarding how to clean my EEG data: 1) Manually remove artefacts first and then apply digital filters OR 2) Apply digital filters first and then manually remove ...
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2answers
630 views

Discrete Sinusoidal to State Space

I'm looking to apply an optimal LQR filter to a discrete signal of the form $x[n]=A\sin[\omega_0n + \phi]+ v[n]$ The amplitude $A$ and the phase $\phi$ are unknown variables I want to estimate using ...
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1answer
30 views

Continuous time double exponential filtering in state space form?

I'm trying to determine the continuous time formulation of the double exponential filter so that I can adapt it more flexibly for my particular problem. Typically, this model is expressed as a pair ...
3
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1answer
115 views

Use samples of Fourier transform as DFT?

Consider the LTI system given by: $H(z) = 1 - \frac{1}{2}z^{-1}+\frac{3}{4}z^{-2}$ Let $x[n] = (\frac{1}{2})^nu[n]$ be the input to the system. We want to find the output for $n = 0,1,...,N_a$, using ...
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1answer
458 views

Bandpass filtering an audio signal with MATLAB's $\tt kaiserord$: unknown new frequency component

I am trying to filter an audio signal with kaiserord in MATLAB, but I'm having a problem. Here is my code: ...
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0answers
12 views

Why are guard bands employed in FBMC even though the prototype filter has near perfect leakage performance?

FBMC employs prototype filter which has a good performance in reducing the spectrum leakage to almost zero but there are a few implementations online where they have still used guard bands on either ...
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1answer
1k views

STFT overlap add method - What am i doing wrong?

i am trying to implement a short time fourier transform of an audio signal to do some filtering (subtract another stft signal using spectral subtraction). I am using a hamming window function with 50% ...
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2answers
73 views

How to apply discrete filters to a signal

Let's say I have a signal like x[k] = [-20 -50 -30 50 30 -60 60 -60 60 10 5 10 5 5], and I want to apply a lowpass and a highpass filter to this signal (separately). For example the impusle response ...
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2answers
133 views

Is There Any Filtering Technique with Element Wise Product Only Instead of Convolution?

Generally we apply a filter to reduce noise from signal. For example if the received signal is $S$ we would get a signal $Y$ with reduced noise applying a filter $W$ with the operation Y= convolution(...
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2answers
65 views

Filter before or after multiplication of two signals?

I have two signals and want to multiply them, e.g. voltage and current are multiplied to get power. The result (e.g. power) shall be a filtered result, e.g. to see the average. Is it better to filter ...
0
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1answer
58 views

Why Would Pre Filtering Measurement Data Affect the Least Squares Estimate?

In estimating parameters in a discrete time model I've often seen the use of filters applied to the input data, before its applied to least squares processing. I've been told that the filters are ...
2
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1answer
203 views

Morphological Gradient Versus Linear Gradient in Image Processing

To obtain the gradient from an image, one can use a linear filter that for example is derrived from the derrivative of a gaussian. Then convolving the image with this linear filter gives you the ...
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0answers
14 views

Differentiating high frequencies if a signal

I have a power signal (in dBm) which contains lots of peaks (around -80 dBm) and most of the time is around -110 dBm which we can call it noise level (obviously with fluctuations). As you know, both ...
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0answers
19 views

remove \ minimize first side lobe ringing artifacts due to data truncation

I have a truncated data set that I need to transform, for example: ...
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0answers
90 views

Fusing like data from multiple sensors using kalman filter

I'm new to kalman filters and filtering, and I'm working on a personal project where I have multiple readings all providing the same data (3d position in space, provided via computer vision algorithms)...
0
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1answer
39 views

how does the Frequency spectrum of a signal change in the logarithmic space?

I am trying to implement basic homomorphic filtering but I can't seem to understand what happens in the frequency domain when you take the natural logarithm of the function. In Matlab I'm getting not ...
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0answers
32 views

How does the “additive operator splitting” exactly work?

I am reading about the non-linear (or non-homogenous) diffusion method (aka anistropic diffusion method). There are several ways of implementing this method. In all cases, we first need to discretise ...
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2answers
3k views

preprocessing raw ECG data

I need to preprocess raw ecg data in R, here is a sample already standardized. I'm not an expert in signal processing nor experienced in working with medical data, so I need concrete answers ideally ...
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1answer
299 views

Is there a $z$-transform like for variable sampling rate signals?

I'm working with signals with variable sampling rate (the time space between samples is not constant). I know the delay between samples but I don't wont to interpolate the signal. Is there a way to ...
1
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1answer
6k views

Differences between low-pass, band-pass, notch filters

I'm studying image processing and I know that there are different filters you can apply. I don't understand the difference between the low-pass/bandpass/notch filter (or high-pass/band-reject/notch). ...
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1answer
3k views

How do we use signal::filter and signal::butter in R for EEG data?

I am trying to design an experiment to determine the peak amplitude of an EEG signal in response to a stimulus. Till now, our team has been using MATLAB and since we wish to go open source, we are ...