Questions tagged [filtering]

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Multi-channel filter for correlated noise suppression

Short question We need to cancel the correlated noise from recorded datasets, as shown in the figure below, coming from arrays of charge sensitive sensors. I would like to ask to this community to ...
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1answer
18 views

deconvolving a 1d signal using a lookup table of “PSFs”?

assuming I measure a signal that has different PSFs per position in time. for example: ...
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2answers
80 views

Distortion of OFDM signal when using RRC filter

I am trying to transmit OFDM signal in pass-band based on RRC filter, but what I noticed that the signal before the RRC filter is completely different compared with signal after the RRC filter (It ...
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27 views

2nd derivative using gaussian filter (gnu scientific library) - offset?

I am working on an application where I use gaussian filtering (convolution) to smooth a signal and at the same time get the 1st and 2nd derivative in real time. The signal is an equidistant sampling ...
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1answer
33 views

Next steps for analyzing this PWM algorithm and choosing a low pass filtering technique?

The Broadcom BCM2711 GPIO controller used by the Raspberry Pi has a hardware PWM implementation option using an algorithm that provides an average value defined by a rational fraction $N/M$ defined as ...
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1answer
64 views

How to find the best Q format representation?

I'm currently working in a project in which I use the coefficients of a IIR Elliptical digital filter (9th order) and the voice signal from a recording of my cellphone but I'm having issues finding ...
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3answers
41 views

what are some possible reasons of having duplicates in sensor signal? resulting in stair-step signal?

I am using an cellphone application to record cellphone gyroscope signal. I put the sampling rate to "fastest" which means the highest sampling rate the cellphone is able to do. What is strange is ...
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1answer
74 views

Reduce Jitter in Live Kalman Filter

I have a stream of data over time that I have fed into a Kalman filter. This data represents the vertical displacement in time of a vehicle's rearwheel as it travels over a bump in the road. The ...
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1answer
52 views

A filter with low phase shift or no phase shift at all? Which one? [duplicate]

I'm seeking a good advice for a filter. Can you help me? Right now I made my own simple filter. Not sure what I'm doing, but it seems to work. ...
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27 views

Classifying motor imagery from EEG data: Feature selection

I am an undergraduate student who is trying to classify motor imagery from EEG data! I have no experience working with EEG or any neuroscience background, I only have a very basic knowledge of how ...
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10 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 (...
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1answer
116 views

Filter: IIR Filter

How IIR Filter coefficients formula derived? for LPF, HPF, BPF, BSF there are coefficients formula for a0, a1, a2, b0, b1. How it came? I would like to know the derivation for all those coeffs w.r.t ...
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159 views

High Pass Filtering and Noise

I have the following code: ...
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1answer
17 views

Image Filtering by Averaging Similar Areas of the Same Image - Patch Based Processing

I heard of filtering algorithms which, to filter an image specific area, find similar areas in the image and average them to reduce the noice of the original area. E.g. an edge of a house can be more ...
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3answers
89 views

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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33 views

How to build intuition for tuning a Kalman Filter?

I'm working on designing a Kalman Filter for more accurately predicting the position of a ultrawideband RFID tag in an indoor space. Before testing with live data, I've been playing with randomly ...
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34 views

Apply a butterworth filter to columns of a large dataframe

I have a large dataframe (7200, 132) and each column is a signal. I want to apply a butterworth filter to each signal, however, I'm not sure how to do this in Python. When I do it in matlab I can ...
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1answer
39 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 ...
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18 views

Supression of sinusoidal interference

I have a bit of project that I'm doing for SIN interference removal. Just not sure Am I doing everything correct: Fs = 1000; Ts = 1/Fs; order = 12; t = 0:Ts:1-Ts; x = sin(2*pi*4*t); noise = ...
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1answer
226 views

How determine the delay in my signal practically

I am trying to practically determine filter group delay so that I can try to reduce or adjust for it. I have tried all kinds of methods but still can't get the right result. I know that theoretically ...
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1answer
37 views

How to get discrete values from a nosiy data set that have a trend?

I have a sensor that produces values over time (appr. 50/sec). I visualized these values (X axis is the time), this can be seen on the picture, measurement A and B - these are two independent ...
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1answer
71 views

Transfer function given as z-Domain fraction: gain calculation

I am stuck on a question regarding transfer functions. I have the answer and have attempted the question but am having trouble solving it. Q: Given the transfer function of a digital filter is (5z-5)/...
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1answer
43 views

How to quantify phase distortion of a filter specific to a signal?

For example, a EKG input signal is filtered with a known transfer function that does not have linear phase. How do you quantify the phase distortion of the output signal given you have the input? I ...
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2answers
81 views

Meaningful output of FIR filter output

I have implemented FIR filter using tapped delay line method. I start getting output as soon as first input sample is passed to it, I am wondering from which sample I will get the proper output(...
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36 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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2answers
73 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 ...
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1answer
54 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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2answers
109 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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1answer
162 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
58 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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20 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
162 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
109 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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58 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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106 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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138 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: ...
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17 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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2answers
91 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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1answer
108 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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2answers
159 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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1answer
255 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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1answer
54 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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1answer
58 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 ...
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2answers
174 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 ...
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1answer
74 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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46 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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1answer
50 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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1answer
210 views

What is the difference between domain and range filtering?

In the context of image processing, I have heard the expressions "domain filtering" and "range filtering". What do these terms refer to? What is the difference between them?
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349 views

Causal unstable system turn into stable anticausal?

I would appreciate it very much if someone would be able to provide some clarity, help or comment on this problem. I have been reading several papers on time series identification such as https://www....
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1answer
44 views

What is used to initialise difference equations that require data from the output?

Given some difference equation for a filter like $y[k] = ax[k] + bx[k-1]+ cy[k-1]$, how would you initialize it? Since it needs an old output value (feedback) to calculate the new output value, it ...

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