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.
347
questions
0
votes
1
answer
75
views
How to demodulate a bit sequence that is offset-modulated with a complex exponential?
I have a discrete-time complex exponential
$a[n]*(\cos(\omega*n/N) + j \sin(\omega*n/N)) + b[n]$
where $a$ is constant and $b$: $\{0,1\}$
So it is basically an offset-modulated sequence of bits and I ...
- 147
0
votes
0
answers
25
views
Using python to remove Gaussian noise and a high frequency signal from a audio file
I have an audio file where people are talking, and Gaussian noise and high-frequency signals have been added to the file. My goal is to remove the noise from this file using Python. For this ...
- 1
0
votes
2
answers
41
views
Transmitting data with QPSK using an SDR
My question assumes that I want to transmit some data using QPSK using and SDR.
The SDR will be fed with IQ data and this will transmitted at a sample rate Fs and be up converted to a carrier ...
- 1
0
votes
1
answer
40
views
Characteristics of linear systems in the time and frequency domain
Why is the output signal obtained through frequency response different from the other two.
...
0
votes
1
answer
59
views
Filtering in time domain vs filtering in frequency domain
The signal is an impulse repsonse. I am filtering the signal using a windowed sinc filter in both frequency and time domain. I am interested in knowing the differences between the two methods and ...
3
votes
1
answer
164
views
What's the point of differential beamforming?
I recently got into differential beamforming, in particular into the work of Benesty and Cohen. It seems to me that differential beamforming is something that just "takes place" when ...
- 98
0
votes
2
answers
81
views
Upsampling of a signal
A low-passed signal, bandwidth limited to 4KHz is originally sampled 10 KHz. If I want to resample it at 20 KHz, I take these steps. Are these correct? Am I missing an step?
First we need to filter ...
- 77
1
vote
0
answers
106
views
How to get an impulse response of a MIMO system?
So I have data vectors from a MIMO system and I wish to see the impulse response
Any idea how I can proceed with this?
user69318
0
votes
1
answer
92
views
What does a Gabor filter "filter" out?
Almost all of the searches online have returned results related to image-processing, but I am looking for a more rudimentary example with some physical intuition (eg; a high-pass filter only lets the ...
- 45
1
vote
2
answers
174
views
Why does convolution give the output of a passing a signal through a filter?
I have a rudimentary understanding of Convolution, the Convolution Theorem and why the output z(t) of an LTI system can be found using the convolution of input signal x(t) and the impulse response h(t)...
- 45
0
votes
0
answers
57
views
single tone -> multi bandpass filter -> incorrect output
background:
Trying to filter out all other signal frequencies except -> signal whose frequency can be in multiple's of 16Hz {16,32,48.......160].
so started experimenting with a single tone [no ...
1
vote
0
answers
271
views
How to recover the LTI system step response by the known output and input signals?
Having the input signal as a step-like pulse and the output as its distorted version after passing through the system:
is it possible to somehow recover the step response of the system?
In the Figure ...
- 355
0
votes
1
answer
130
views
ICWT filtering signal with a cut-off frequency
In ssqueezepy, by finding a certain scale is it possible to do an icwt only for the scales above (or bellow) ? For exemple if I have a double sin (with $f_1$ and $f_2$), by taking the frequency $f_c$ ...
- 11
1
vote
0
answers
39
views
Does filtering by wavelet decomposition and reconstruction introduce a phase shift in the filtered signal?
I am removing low frequency noise from a signal using Matlab using the DWT and then reconstruction at a specific level:
I am removing the approximation signal at level 10 which approximates the low ...
- 11
0
votes
1
answer
72
views
How to find system output by its step response?
Inspired by this post, I tried to reproduce the procedure described in the answer in Python considering rectangular pulse:
...
- 355
1
vote
1
answer
85
views
What is the necessity of shifting the impulse response of a filter to the front of the time domain buffer and windowing?
I was reading the answer to this question provided by Phil Karn.
In the answer, it has been said:
Ensure that the impulse response of your lowpass filter is shifted to the front of your time domain ...
- 117
1
vote
3
answers
198
views
How to estimate the local trend in a signal?
I need to remove trend from my time-series which looks like the following images.
However, I want to estimate the trend before removing it. Hence directly removing it won't do it.
The simple ...
- 357
2
votes
1
answer
50
views
Filtering after a phase domain ADC
While researching receiver architectures for the demodulating constant envelope signals like a GFSK, I stumbled over the concept of phase domain ADCs, where after
$$\boxed{\text{LNA}}{\longrightarrow}\...
- 21
1
vote
0
answers
94
views
The correct way to perform signal processing on S-parameter data
I have a question to ask you which has been bugging me as of late.
I have s-parameter data with 5001 samples acquired from a vector network analyzer. I am trying to 'gate' this s parameter data, i.e. ...
- 41
2
votes
1
answer
314
views
Autocorrelation function of a filtered periodic signal
I'm having trouble with this exercise.
The signal $x(t)= \cos(2\pi f_0 t)$ is sent in input to a non-linear system with input-output relationship equal to: $g(x)= 0$ if $x<0$ and $g(x)=3x$ if $ x &...
- 75
0
votes
0
answers
125
views
Is this how to show decimation in the frequency domain?
Let's say I have a discrete-time signal $y[n]$ that is passed through an Ideal Lowpass Filter (impulse response $h[n]$) to get $y_1[n]$. The filter has cutoff frequencies at $\pm \pi/N$ rad.
Now this $...
user64710
1
vote
2
answers
161
views
Correct baseline for slow sinusoidal noise signal
I acquired some noise signal (5GHz samplerate, 520 samples) data from a device and recognized that it is not gaussian distributed. There seems to be some slow sinusoidal signal underlying. I tried to ...
- 51
0
votes
1
answer
95
views
Bandpass filtering EEG and getting weird distortions, parameter issue?
I am trying to bandpass filter an EEG signal, nothing fancy but it's coming out pretty distorted.
EEG data is taken from forehead. Sampling rate is 250 Hz. Cutoff is 2.5 Hz & 120 Hz.
Tried in both ...
0
votes
0
answers
15
views
Extract PVC feature from singal to train the ML model with PVC characteristics
I have ML model which is trained on Afib, Normal, Other - 3 class. Currently when I am testing the model with unseen database, sometimes it identify PVC singals as Afib class.
For example -
enter ...
0
votes
1
answer
117
views
What highpass filter is implemented in Audacity?
When I selected highpass filter effect in Audacity (an open-source audio editor), it lets me choose the cutoff frequency and the roll-off but it doesn't specify which filter type is used (IIR ...
- 398
0
votes
1
answer
105
views
FIR filter for flipping the phase in negative phase
I have built up a FIR filter based on least square approach.
I deploy the IDFT matrix $$F_{inv}$$ in above document page 7 and the desired response for compensated is H_F, the objective is
$$
min_{...
0
votes
2
answers
67
views
How to achieve a DC portable power source with low noise in 400 MHz frequencies
I am working on an SDR composed system that is plugged into a Raspberry Pi board powered by a 5V DC Power bank. The SDR is configured to measure a signal around 400 MHz.
The noise floor measured by ...
- 98
0
votes
1
answer
93
views
What does frequency filtering actually practically mean?
I've got an electronics circuit which was filtering between a Passive HPF stage (1uF and 330K) and an Active LPF stage (4.7uF and 10K). As you can see it was filtering between 0.48Hz and 3.38Hz, and ...
- 105
0
votes
2
answers
66
views
Method for splitting time-sampled signal into two signals
Update: the yellow area in the graph below can be ignored, it shows power produced. I'm only interested in the blue line, and how to separate power consumed by the heating system from the rest.
I have ...
- 121
2
votes
1
answer
131
views
Selective Discrete Time Derivative Filter
I have hit a problem which could be probably solved via discrete time derivative filter able to calculate the derivative of two specific harmonics of the input signal (namely frequencies: $f_1 = 100\,\...
- 375
1
vote
1
answer
72
views
What's the best way of modeling 3d target motion with only 2d angle observations?
A maneuvering target is flying in 3d cartesian space, but a sensor (passive infrared or mic array, etc.) can only observe it in polar coordinate with 2d orientations
(azimuth, elevation). For ...
- 11
2
votes
1
answer
120
views
Approaches to work around differing signal lengths when using Kalman filter
I have a set of vector valued signals $\boldsymbol{y}_{1:T}$ where each $\boldsymbol{y}_k \in \mathbb{R}^{v_k}$. Each signal is potentially of different dimensionality. I'd like to apply filtering and ...
- 23
2
votes
1
answer
627
views
Why does sequential update of Kalman Filter work when you have multiple sensors?
If you are using a kalman filter with multiple sensing sensors there are two ways to fuse them.
One way is doing a single observation step where you include all the sensors in a single vector and a ...
- 818
5
votes
2
answers
321
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?
...
- 488
1
vote
0
answers
27
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 ...
Lerian Acosenossa
0
votes
1
answer
156
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:
...
- 293
4
votes
0
answers
96
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:
$$y_a(t)=y(t)+jH(y(t))=x(t)*h(t)+jH(x(t)*h(t))=x(t)*\left(h(t)+jH\left(h(t)\right)\right)$$
...
- 1,084
2
votes
1
answer
183
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 ...
- 124
0
votes
1
answer
363
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 ...
- 1
0
votes
1
answer
214
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 ...
- 3
0
votes
0
answers
61
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:
...
- 46
1
vote
1
answer
107
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 ...
- 11
7
votes
3
answers
83
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 ...
- 173
1
vote
1
answer
236
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
67
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....
- 11
0
votes
2
answers
130
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 ...
- 143
0
votes
1
answer
36
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
509
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 ...
- 21
0
votes
1
answer
174
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 ...
- 293
5
votes
2
answers
326
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 ...
- 425