Questions tagged [filtering]

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1answer
1k views

How to remove ECG artifacts from EMG data?

I'm new to signal processing and try to analyze EMG data from pectoralis major and other respiratory muscles. Unfortunately, there are strong ECG artifacts in all recordings and I don't know how to ...
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0answers
12 views

Accelerometer drift: What hardware-level signal conditioning operations are being performed under the hood of a MEMS accelerometer chip?

I'm in a debate with a peer who says that filtering accelerometer signals at the chip-level has nothing to do with mitigating the problem of drift Often, additional software-level filtering is ...
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2answers
57 views

DSP signal filtering and number formats

I'm working on a dsPIC33, using Audio Codec Board - Proto to read audio samples and for reproduction. In order to implement a relatively simple signal processing algorithm, I'm reading audio samples ...
0
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1answer
22 views

Difference between the average operation and the application of the equivalent LPF

I would be glad if someone could answer my question. I have a bit stream of data and I want to extract the low frequency component. When post processing the data I can calculate the average value over ...
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0answers
15 views

Training of adaptive filters

I am trying to understand adaptive filters as I want to implement a denoising algorithm based on them. Do we need to train all thee adaptive filters before they start their actual process? For the ...
3
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1answer
57 views

Alternatives to offline Kalman filtering

Recently I got into vehicle models and filtering in general and immediately faced with the following question. I have the recorded GPS data from car driving on a highway. However, there is a ...
0
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1answer
69 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 ...
7
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2answers
190 views

Using oversampling to increase resolution of a DC-signal as input

Currently I'm working on a project which uses oversampling to increase the resolution of a 12 bit ADC to a maximum of 16 bits. My goal is to fully understand the theory behind oversampling and why it ...
1
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1answer
134 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 ...
2
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3answers
4k 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 ...
0
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1answer
169 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 ...
1
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1answer
333 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
2k 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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0answers
102 views

Linkwitz-Riley Allpass filters of Nth order from cascaded SVF second order sections

I am in the process of implementing a Linkwitz-Riley filter of 16th order. (LR-16, 96dB/oct) I am using 2nd order SVF sections with three modal outputs on each section. (LP, BP, HP) I am looking to ...
1
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2answers
189 views

Windowing after filtering a discrete signal to get it back to its original length

What happens if you filter a discrete bandpass signal of length $N$ with a bandpass filter (Hann truncated sinc) of length $L$ and apply a window of length $N$ to the filtered signal of length $N+L-1$ ...
0
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1answer
62 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 ...
0
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1answer
209 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 ...
0
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1answer
27 views

Help or suggestions with Line detection in microscopy images

I'm doing a personal project in which I want to select some very specific lines in a microscopy image. The first picture is the raw image, the second picture is the image for the lines (in yellow) I ...
3
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1answer
112 views

Derivation of the lowpass to bandpass transformation

I have a basic question. The "well known" lowpass to bandpass transformation is $$ s \longmapsto \frac{\bar{s}^2 + \omega_1\omega_2}{\bar{s}(\omega_1 - \omega_2)}, $$ which gives a bandpass ...
1
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3answers
60 views

Seeking advice on how to denoise a video from poor CCTV lighting

I have grainy CCTV footage that will need some amount of clean up. I request for ideas on the best way to clean out the noise. I am attaching a frame extracted from the video here for hints on the ...
0
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1answer
86 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 ...
1
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1answer
488 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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2answers
76 views

Scipy Butterworth highpass filter results in distortion and bloated output

Trying to use Scipy Butterworth filter to filter frequencies below 54 Hz from audio files. Audio files are stored as WAVs. Sample rate is 44100. When I try using this filter the result is distorted (...
1
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3answers
102 views

Noise added to a Random Process

if we have a discrete random process \begin{equation} x\left(n\right)\:=\:0.2x\left(n-1\right)+w\left(n\right)+w\left(n-1\right) \end{equation} where $ w\left(n\right)$ is a noise with a mean $ m_w=0....
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2answers
615 views

Undoing a filter operation in MATLAB

Out of curiosity, is it possible to actually reverse a filtering on MATLAB. For example, if I have ...
0
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1answer
64 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 ...
0
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1answer
128 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) ...
0
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1answer
63 views

Classical spectrum analyzer model

I am trying to reproduce a numerical model of classical spectrum analyzer, described in "Fundamentals of Spectrum Analysis" by Christoph Rauscher. Classical model consists of a few local ...
1
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3answers
79 views

How to practically correct for group delay imposed by a digital filter (Python)

I'm using Python to filter a signal using a Butterworth filter (scipy.signal.butter) and subsequently passing this through a forward-backward filter with cascaded second order sections (scipy.signal....
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0answers
13 views

Can I use BRISQUE to compare different filtering techniques for the same acquired image?

BRISQUE compares your image with a pre-learned model with opinion scores. I am not sure about this but would image resolution affect the result of BRISQUE? Moreover, if I have 2 filters and I would ...
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0answers
23 views

Removal of parallel-line like streaks

Just wondering what image processing techniques can remove some artifacts of parallel-line like streaks, which are shown in the red box in the above picture. I was thinking about removing it from ...
2
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1answer
29 views

Deriving a Kalman Filter Equation for a Linear Gaussian Filtering Model with Non Zero Mean Noise

I am trying to answer an exercise question from the book Simo Sarkka - Bayesian Filtering and Smoothing. The question is: Does anyone know if there is a resource that has the solutions for this book?
0
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1answer
104 views

Butterworth filter of the acceleration and drifting displacement problem

I am only mechanic engineering and I need to filter my acceleration from MEMS mobile phone which has a noise and drifts. Here is my data. Acceleration vs time from an app mobile phone ...
0
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1answer
45 views

Recoverable continuous function after average sampling

I have a personal interest in this question, but I don't know if it is unfounded. Suppose I have a continuous function x (t), which is sampled using an average sliding window, which performs a ...
0
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1answer
92 views

Applying zero-phase filtering in the frequency domain - also works in real-time?

In my application a filtering in the frequency space is desired. I designed two high-pass filters: $h_1$ Butterworth IIR filter, and $h_2$ FIR. I designed them using Python's ...
3
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1answer
89 views

Use of the harris-Moerder Nyquist Pulse Shaping Filter

I became aware today through fred harris' excellent presentation at the DSP Online Conference (https://www.dsponlineconference.com/) of the harris-Moerder pulse shaping filter which was published 15 ...
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0answers
26 views

Is convolving a signal by a wavelet (in time domain) equivalent to wavelet filtering?

I am a noob in signal processing. Please help me understand if the following relation is true or not: ...
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5answers
158 views

An intuitive explanation as to why a matched filter is time reversed?

It easy enough to study correlation, and matched filters. But the challenge I see unmet anywhere to date and which I struggle to meet myself is a simpler presentation, to with more difficult task I ...
1
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1answer
130 views

Apply “non-causal” filter buffer-wise, a.k.a “soft real-time filtering”

I am dealing with digital filtering of signals, both offline and in real-time. Typical filtering purposes are highpass filter or bandpass filter. So far I worked on prerecorded signals (e.g. ...
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0answers
21 views

Low pass filter output

What will be the output when a square wave of time period 1sec is applied to the input of LPF of cutoff frequency 1Hz. Please help me, I am not getting the exact expression. What if cutoff of LPF is ...
0
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1answer
6k 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 ...
1
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1answer
66 views

Respiration (breathing) signal movement artifact removal

Situation: I have breathing data of participants who have done different things during the study which caused their breathing change; watching mindless video to which resulted in unconscious regular ...
4
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2answers
2k views

Extended Kalman Filter (EKF) for Non Linear (Coordinate Conversion - Polar to Cartesian) Measurements and Linear Predictions

I'm new to Kalman filtering and state estimation and I'd like some guidance on EKFs. Currently, I'm trying to use a linear prediction model coupled with nonlinear measurements to estimate the state ...
1
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2answers
76 views

Question about ideal filters

Following shows the discrete time Fourier transform of an ideal low pass filter with cutoff frequency $\omega_c$: $$H\left(e^{j\omega}\right) = \begin{cases} 1, & \text{if $|\omega| \le \omega_c$...
2
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3answers
153 views

Deconvolving a 1d Signal Using a Lookup Table of Kernels

assuming I measure a signal that has different PSFs per position in time. for example: ...
1
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1answer
40 views

Which one can be accompanied by linear filters?

I have a matrix : \begin{bmatrix} 1 & 2 & 3\\ 1 & 4 & 5\\ 2 & 6 & 7 \end{bmatrix} After doing operation 1 , I get \begin{bmatrix} 0 & 0 & 0\\ 1 & 2 & 3\\ 1 &...
6
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1answer
196 views

A Simple Algorithm to Filter / Smooth / Denoise a Noisy Staircase Graph

Is there a way to remove the noise and smooth the graph into a staircase graph.
0
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1answer
30 views

How can I plot Wiener filter's behaviour for different taps (memory filter)?

What's the expected behaviour of Wiener Filter for different taps (memory filter) , when input signal is a sinusodial tone? Do you have any idea how I can plot or simulate Wiener Filter's behaviour (...
0
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1answer
22 views

How does Correlation for 1D Signals work?

On page 2 of the slide, I don't understand the example. Like $j$ and $s$ are both on the x-axis, what does j+s mean? The filter is $(f(−1), f(0), f(1)) = (−0.5, 0, 0.5)$. How can we use it? Could ...
0
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1answer
28 views

How does filter works in noise reduction?

On page 22 of the slide, the 1D array is [1, 1, 1, 1, 1], but the dots are uneven. Then why their values are the same? What's the value of the point that the arrow is pointing at? Though it gives ...

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