Questions tagged [filtering]

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5 votes
2 answers
249 views

Amplifier Placement in a Wireless Receiver

In the context of wireless receiver system design, what is the optimum choice of amplifier placement? Should the received signal be amplified first then filtered or should it be the other way round? ...
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0 votes
0 answers
38 views

Applying 1D wiener filter radially to 2D image

I am new to image processing. Using python, I have constructed a 1D wiener filter from the power spectrum of a Noisy Image, with Noise as a function of k. They both have the same dimension which is ...
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1 vote
0 answers
15 views

How to design a phonographic sound filter in python?

I'm making a phonographic filter or simulator to make one of my songs to sound as if it was recorded on a phonographic cylinder. Two important things about phonographic recoding is that sound gets ...
user avatar
0 votes
1 answer
64 views

Real time processing in matlab

I have to extract a particular frequency range from an audio signal. For that I am using an FIR filter of order 50 and it is written in MATLAB as below: ...
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4 votes
0 answers
52 views

Combination of IIR filter with Hilbert transform

I am familiar with the combination of the FIR filter with Hilbert transform, leading to the analytic signal: $$y_a(t)=y(t)+jH(y(t))=x(t)*h(t)+jH(x(t)*h(t))=x(t)*\left(h(t)+jH\left(h(t)\right)\right)$$ ...
0 votes
0 answers
14 views

image preprocessing(filtering) : before or after undistortion and stereo rectification

I'm currently working on a stereo visual-slam program (using OpenCV). After I get the images, there are 2 preprocessing steps to be done : A) Undistort the images + stereo rectification B) Some ...
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2 votes
1 answer
138 views

How to implement the recursive FIR filtering of a signal with zero boundary condition?

Now I have a signal $f(k)$ with $k=0,1,\ldots, N-1$, and $f(k)=0$ if $k<0$ or $k>N-1$, that is, the signal satisfies the zero boundary condition. Then by convolving this signal with a symmetric ...
0 votes
1 answer
43 views

Demodulate qpsk with gnu radio

I'm trying to demodulate a qpsk signal with gnu radio. The signal is from the meteor satellite on 137MHz https://www.sigidwiki.com/wiki/Low_Rate_Picture_Transmission_(LRPT). I recorded the signal with ...
0 votes
1 answer
64 views

Signal filtering with rrcos filter doesn't seem to work

I'm trying to learn some signal processing and recorded some iq data from the meteor satellite which transmits data with qpsk. I read the file with python and tried applying a rrcos filter on the ...
0 votes
0 answers
42 views

Weird filtering result

Im filtering some ecg data for mainly just powerline noise (50 Hz), but get some weird result between the R-peaks (main spike). I have just done some tried with some basic filtering like this: ...
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1 vote
1 answer
32 views

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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7 votes
3 answers
65 views

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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1 vote
1 answer
45 views

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 ...
0 votes
1 answer
42 views

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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0 votes
2 answers
61 views

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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0 votes
1 answer
24 views

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 ...
2 votes
1 answer
53 views

how to plot analog filter impulse responce and frequency responce?

I an new to signal processing, working on a UWB rada data this data has a shape of frames for whcih every frame (list) has 164 values, I want to pass a band pass filter with the 1hz and 5hz ...
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0 votes
1 answer
98 views

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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6 votes
2 answers
165 views

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 ...
0 votes
2 answers
134 views

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 ...
2 votes
1 answer
59 views

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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-1 votes
1 answer
50 views

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 ...
-1 votes
1 answer
184 views

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 ...
0 votes
1 answer
43 views

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 ...
3 votes
1 answer
95 views

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 ...
0 votes
0 answers
119 views

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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0 votes
1 answer
83 views

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 ...
2 votes
1 answer
180 views

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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1 vote
1 answer
149 views

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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6 votes
1 answer
489 views

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 ...
1 vote
1 answer
576 views

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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4 votes
1 answer
211 views

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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2 votes
3 answers
249 views

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 ...
1 vote
1 answer
30 views

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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5 votes
2 answers
305 views

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 ...
0 votes
1 answer
301 views

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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1 vote
1 answer
65 views

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 ...
  • 105
1 vote
1 answer
76 views

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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0 votes
1 answer
44 views

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 ...
9 votes
4 answers
1k views

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), ...
0 votes
1 answer
204 views

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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-1 votes
1 answer
64 views

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". ...
  • 501
1 vote
1 answer
407 views

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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0 votes
1 answer
166 views

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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1 vote
0 answers
102 views

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: ...
5 votes
1 answer
104 views

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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1 vote
1 answer
75 views

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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2 votes
1 answer
335 views

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 ...
1 vote
1 answer
173 views

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, ...
0 votes
0 answers
21 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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