Questions tagged [filtering]
Filtering is a way to process an input signal so that the output signal has interesting features enhanced or unwanted features reduced.
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How to remove the unknown intervention from the signal (Octave)?
we have a signal recording and there are always interventions, I think it is not a noise, since it is not continuous but occurs in intervals, with 25 Hz (please see below). It is not affected by the ...
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How to exclude diffuse moving features in a stack of images
I have some stack of grayscale reconstructed images represented as a 3-dimensional matrix DPC with dimensions [Nz,Nx,Nt]. A ...
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Savitzky-Golay filtering (not smoothing) in real time
I would like to filter some data in an online sense i.e.
$$y(t) = a0 + a1*y(t-1) + a2*y(t-2) + ... $$
the order not important.
My understanding of the SG is that it is really a smoother - I have to ...
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Filtering out correlated data from dropouts
I have two 10Hz signals coming from an analyzer. There is a correlation between dropouts in the current applied and the signal that it produces. The correlations occurs sometimes, but not all the time....
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Butterworth filter cutoff attenuation is not exactly 0.707(-3dB)
The documentation of scipy Butterworth filter says its cutoff attenuation is 0.707(-3dB). To validate this, I created a square wave signal, performed FFT and implemented a bandpass filter with a band ...
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Why is the second difference matrix of size n-2 x n in l1 trend filtering?
The l1 trend filtering is expressed by taking $||Dx||_1$ where D is the second difference matrix why is taken of size (n-2)xn rather than circulant matrix of size nxn. I have implemented in both ways ...
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how to plot analog filter impulse responce and frequency responce?
I an new to signal processing, working on a UWB radar data this data has a shape of frames for which every frame (list) has 164 values, I want to apply a bandpass filter with cutoff frequency of 1hz ...
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Need for rectification in cochlear implants
In cochlear implants, the input signal is fed to a set of bandpass filters and is then half-wave rectified and low pass filtered to estimate the envelope signal.
What is the need for doing ...
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The Effect of Spatial or Temporal Averaging on Noise Properties
I generate two noise images using MATLAB's function imnoise().
If I average the two noise images, the resultant image looks like the original noise
image but only ...
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BPF Filtering with DSP IIR Realtime C++ filter library
I am working with complex samples, I have a main signal at 630KHz, my Fs is 1.26MHz and BW is 12.6KHz.
If I plot a frequency-magntitude spectrum it looks like this:
As you can see along with my main ...
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How to find point of inflexion of a digital signal?
Let's say I would like to find a point of inflexion of a digital signal which has been gathered via sampling of a continuous time domain signal with sampling period $100\,\mu s$. The digital signal ...
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localization with TDOA under Doppler shift
In a localization system, I use the TDOA (Time Difference of arrival) method. The transmitter is moving at a speed v and its communication signal is received on 3 receivers at different times. For a ...
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Fourier Transform High Pass Circular Filter Intuition
The situation
I need to apply a high pass filter to an image. The approach I'm following uses Fourier transform to apply a circular filter which would eliminate low frequencies.
Say I have a frequency ...
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Gaussian Blur For Entire Image
I am trying to simulate the blurring process (defocus) of a sinusoidal. For this I have build my own Gaussian filter and performed the convolution in Fourier domain.
The result of the blurred signal ...
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A filter removing forbidden information in the stop-band
Is it possible, and how could it be done, to make an extension of filters that converts the signal in the filter's stop-band into noise with no information content or at least with zero correlation to ...
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Design an FIR linear phase lowpass filter using windows to meet the following specifications. What is given in the question? How to start solving it?
What is given in this question? I have not seen a single solution of these types of filter design problems in the internet. So I am confused, how do I proceed solving these problems. Can you guide me ...
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What's the correct way to align two signals downsampled at 10 Hz?
I'm trying to build a dataset where one of the features is a signal which has originally been sampled at 500 Hz, while another feature is a signal which was sampled at 100 Hz. I want to downsample ...
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Does it make sense for my filter to depend on the discrete sample variable n?
I feel a little nervous asking this question as I am not sure if know what exactly I am trying to ask. But please see if you can help.
Ok, I have a filter whose output grows as long as the input is ...
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Aritifacts of time-varying IIR filters
I'm doing something like spatial audio algorithm using IIR modelled HRTFs. At each frame I get a direction information with azimuth and elevation, and then I have to find or interpolate the ...
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Deblurring 1D data using direct inverse filtering
In my assignment I have been given recorded temperature over a period of time (193 values) and the impulse response (5 values with n=0 corresponding to the middle value.)
Data: data.csv
...
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Find coefficients of optimal Wiener filter of length 2
I need to find the coefficients (impulse response) of a FIR Wiener filter with length equal to 2.
I have a gaussian white noise signal that is generated using the Standard Normal Distribution (mean = ...
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Sound activated recording and advanced filtering on Raspberry Pi
I'm making a Raspberry Pi bat detector using a USB-powered ultrasonic microphone. I want to be able to record bats while excluding insects and other non-bat noises. Recording needs to be sound-...
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Detrending PPG signal
I'm filtering a raw PPG signal sampled at 100sps
After applying a bandpass filter my signal looks like this
As you can see, It has a trend (a low pass component which is not in the desired signal).
I ...
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How to apply an atmospheric attenuation filter in the freq domain and then convert the filtered signal back to the time domain?
This question is a part of a more general question the answer of which I don't know -
How to apply a filter in the freq domain and then convert the filtered signal back to the time domain? Well, I ...
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Constructing frequency domain filter from a 2d spatial kernel
Given a 2d spatial kernel $h$, I want to construct the corresponding frequency filter $H$. In theory, $H$ is simply obtained by calculating the DFT of $h$ using a FFT algorithm. But in practice, there ...
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ANSI S1.11.2004 Octave-Band Filter implementation
I am trying to implement some code to firstly generate an Octave-Band and Fractional-Octave Band filter. I have used MATLAB's octaveFilter method to generate compliant Class-1 and Class-0, 1/1 and 1/...
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RF-Chain Signal Delay for Sensor Switching
Lets have a RF-chain as above with system bandwith from HP corner to the green line say 1 MHz.
The signal accumulates delay as it passes through this analog chain, and due to it being non-liner filter ...
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Pulse shaping with root-raised cosine filter for a non-Gaussian channel
I am here to check whether my line of thinking is correct.
Root-raised cosine (RRC) filtering is one way to minimize intersymbol interference (ISI). Hence, we apply matched RRC filters on both sides ...
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Help identifying filter
Apologies in advance for asking something so basic, this is not my field at all so I'm a bit lost where else to find this info. I'm trying to understand this piece of code that detects sudden drops in ...
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Deconvolution to Remove Gaussian Blur in 1D Signal (Wiener Filtering?)
I've got a set of biology data that I'm trying to denoise (effectively, a population statistic can only be measured convolved with a gaussian of known width)
My problem is this: I can measure (f*g), ...
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Minimum phase conversion with Cepstrum method, how to scale the result?
I am trying to convert a zero phase spectrum (magnidue response curve with zero phases) to a minimum phase spectrum, because I need a totally causal impulse response for FFT spectral filtering, and ...
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Why does applying RRC to the signal increase bandwidth?
Please see this question: Why samples per symbols $\geq 2$ in the GNURadio Constellation Modulator block?. The first answer here says "filtering the signal, you have bandwidth expansion". ...
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Memory efficient filtering with scipy.signal in Python
I have several EEG channels that need filtering, and one channel may reach a recording length of 12 hours or potentially even more. This results in billions of data points stored which, when loaded, ...
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Implementation of Overlap Save Filtering with Decimation
I am trying to implement Matlab code which performs FIR filtering with complex bandpass filter using Overlap Save method and perform decimation as well by using different length forward and inverse ...
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Tile Laplacian Filter in MATLAB
I want to compute the output image by first dividing the image into 8*8 blocks and applying laplace filter separately and combine them but I am not getting the correct output
Here is the code:
...
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Expected value of a quantized noisy signal
I am given a noisy signal $y(t) = x(t) + w(t)$, where $x(t)$ is my desired signal and $w(t)$ is the noise. In my scenario, the noise is very strong, much stronger than the desired signal $x(t)$. ...
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The result if order of two filter are reversed
Apply the Composite Laplacian Filter first, then apply the gaussian filter.
Apply the gaussian filter first, then apply the composite laplacian filter.
My work as below:
Here we assume the original ...
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Bandwidth of PSK modulated signal
What does it mean that the bandwidth of PSK modulated signal without applying any filtering or shaping of the pulse, is equal to the sampling rate with "1st lobe" equal to two times of ...
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Offset after Butterworth bandpass filtering
guess I'm stuck with this filtering problem and I'm thinking it has something to do with my raw data but I'm not so sure. So the problem is the following, please refer to the figures below, basically, ...
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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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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 ...
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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 ...
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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 ...
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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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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 ...
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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 ...
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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 (...
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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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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 ...
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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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