Questions tagged [window-functions]
In signal processing, a window function is a mathematical function that is zero-valued outside of some chosen interval.
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Coherent Sampling vs Windowing for 50/60 applications
Let's say I need to sample 50/60 Hz signals to find RMS. I can use for example 1kHz sampling frequency. That means 100ms sampling is 5 cycles of 50Hz and 6 cycles for 60 Hz. That's coherent sampling. ...
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0answers
22 views
What is the spectrum of generalised periodic signals assuming mainlobe covers the first two harmonics?
I found this statement in the paper here which I have difficulty seeing why is it true.
Let $H(\omega)$ represent the Fourier transform of a time-windowing function. Assume the width of the mainlobe ...
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1answer
48 views
window function between program and math
I'm newbie on signal processing.
I know when we program python with window function. (just signal multiply with window)
According to Harris paper
I know we change w with different window(blackman).
...
3
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1answer
60 views
Is the DCT prone to spectral leakage like the DFT?
My understanding is that the DCT assumes the input to be an even periodic signal.
This avoids the discontinuity that can occur in the periodic extension assumed by the DFT (see image).
Does this lack ...
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2answers
95 views
Estimate signal parameters for known frequency
Consider real signal of the form:
$$
\begin{align*} x(n) = &\sum_{m=1}^{M} \left( c_m \cos(2\pi f_m n) + s_m \sin(2\pi f_m n) \right) =\\
&\sum_{m=1}^{M} a_m \cos(2\pi f_m n + \phi_m)
\end{...
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0answers
34 views
Variable Window Size of Blackman FIR filter
I am trying to implement an FIR filter with a Blackman window function. The solution I got for my signal filtering problem is to have different window sizes for certain characteristics of the input ...
1
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2answers
51 views
Frequency Support of Window Functions
All window functions, which go from zero amplitude, up, then back to zero amplitude, are all base-band signals. Why is this? Are all functions that have this behavior always band-band aka low-pass?
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1answer
34 views
Zero Meaning a Hamming Window in Matlab
I am still relatively new to signal processing and MATLAB and am working on a short-time fourier transform of some data using a prexisting code. Within the code a Hamming window is produced and ...
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0answers
38 views
Reconstructing a signal from multiple filtered copies using overlapping tapered windows
I have an audio signal that I need to process and analyse in blocks. I've now decided to process it using overlapping non-symetric Hanning windows of length M = 9600 and a hopsize of R= M/2. I zero ...
3
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2answers
86 views
FFT result of windowed cosine function
The frequency spectrum of cosine function is as below.
While adopting a square window function to the cosine function, it is same as implementing convolution of their frequency spectrum as below. The ...
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2answers
114 views
Why could window function help to get more accurate specific frequency amplitude?
In order to calculate amplitude of sinusoidal signal at a frequency around 60 Hz (but may be not 60 Hz), window function is adopted while using DFT.
hk is the coefficient of window function and Kdc ...
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2answers
95 views
How to removed ripples cause by zero-padding in fft?
Desired outcome: Interpolation in frequency domain
Attempts: Zero padding when doing fft
Problem: Ripples in frequency domain appeared after fft with zero padding
Code to reproduce the problem:
...
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0answers
63 views
Gibbs phenomenon, which window to use?
"Rectangular window" and "Triangular window" have gibbs phenomenon
So which window should be used in fir filter design to have minimum or zero gibbs phenomenon
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1answer
25 views
Confusion calculating length of Kaiser window
I am reading Digital Signal Processing Using Matlab by Ingle and Proakis (3rd ed.)
In Chapter 7, Section 7.3,
I am confused why he is adding 1 to main lobe width for calculating length of window.
I ...
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3answers
115 views
Compute Hann window without cos function
In an environment with limited memory and computing power it is interesting to be able to generate a Hann window without using a cache or repetitive calling of expensive functions such as sine and ...
3
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1answer
91 views
What is the difference of windowing functions for FIR filtering?
What is the difference of window types such as Hann, Rectangular, Hamming in the application. Is there such a thing that the one is better than the other?
There will be an oral exam for DSP course ...
0
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1answer
121 views
WOLA vs Simple Hamming Window on signal before FFT
Im working on a project in which I should FFT a signal coming into my FPGA from ADC.
I want my FFT to show the peak values as clear as possible without the side lobes.
The solution should be straight ...
0
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1answer
35 views
Length of Hamming Window to Resolve a Harmonic
I am trying to answer the question:
"Given a single-sourced pitch signal with a fundamental frequency of 440Hz and a sampling rate of 44100Hz how long should the Hamming window of the STFT analysis ...
0
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1answer
62 views
Blackman-Tukey Autopower equation
I am looking over Blackman-Tukey method for Autopower.
It uses the DFT after a window is applied on a autocorrelation.
$$
Power Spectrum = \frac1{2\pi} \ \sum_{(k=-(N-1))}^{N-1} w[k] R[k] e^{-i\...
0
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1answer
27 views
Deriving expression for the DTFT of a rectangular window
Looking at the picture above, how did the author get from point A) to B)?
My Approach: Multiply A) by $e^{j\omega/2}/e^{j\omega/2}$. Now I am stuck with simplying the numerator.
0
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1answer
33 views
LowPass Filter & Window *Img & Code* - Frequency Response has no lobe roll off
Not sure if I am doing something silly but I am not seeing lobe roll off on the frequency response of my windows and the low pass filter I made in MATLAB.
Please can you help ... several hours just ...
0
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1answer
33 views
High Order Filtering [duplicate]
Which window has better performance for higher order filtering?
A. Rectangular window
B. Hamming window
C. Kaiser Window
D. Hann Window
Can anyone please answer this with explanation.
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0answers
38 views
Fundamental component estimation
I am dealing with phasor estimation (fundamental component extraction primarily), and i am using sliding window DFT (which happens to be very popular for phasor estimation). Now at nominal frequency (...
2
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2answers
128 views
Effect of changing sample rate, window duration and zero padding on DTFT and DFT
Let $T$ be the window duration, $N$ be the DFT size, $F_s$ be the sample rate, and $F_{max}$ be the frequency of the highest bin. In the context of image below:
halving the $F_s$ (keeping $T$ ...
0
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1answer
64 views
Smooth signal with Hanning
I have an acceleration record and i want to smooth it's spectrum by using a hanning window with Bandwidth=0.5 Hz.
How could i do that?
Example in python/matlab will be appreciated!
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4answers
177 views
Hanning Window Bandwidth
I am using scipy's "scipy.signal.hanning" to determine a hanning window. This method returns an array with the window and specific number of points based on your input.
More info: https://docs.scipy....
0
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2answers
120 views
Confused in Smoothing a signal in the Frequency domain
First of all i am new in DSP, so i have no solid education in the field.
I have convert my time domain acceleration-seismic data to frequency using DFT and i am trying to smooth the DFT data, in ...
1
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3answers
122 views
Rectangular vs Hann windowing
I'm trying to create a basic digital signal processing pipeline, to manipulate a WAV file.
Nothing fancy, I'm just looking to apply some filtering.
My first attempt was to divide the input signal to ...
1
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1answer
56 views
Harmonic Product Spectrum from FFT output to the fundamental frequency
I'm trying to do the HPS algorithm on my FFT output, but I'm stuck here.
My signal is from a bass (cable), 16bits, 48.000Hz.
I split in time domain the array of the whole record into multiple arrays ...
0
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1answer
69 views
Using overlap add for drawing spectrogram
I'm confused with overlap-add (OLA) in the following two scenarios
filtering/convolution an input signal;
applying an STFT on input signal only and draw its spectrogram.
When applying OLA to ...
0
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3answers
118 views
Windowed N-point FFT
In the previous question,
Smoothing in frequency domain and impulse reponse of the filter in time-domain
I guess I have made a mistake in-terms for applying windowing to FFT.
After reading "...
0
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2answers
105 views
Smoothing in frequency domain and impulse reponse of the filter in time-domain
I have a low-pass signal in frequency domain, $$\left[f_{min}=0, f_{max}=20\,\mathrm{GHz}\right]_{n=100}$$
After re-configuring the input signal as
$$X=\left[-f_{max},\ \dots\ -f_{min},\ \mathrm{DC},...
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2answers
146 views
Advantage of applying a Window Function in Analysis and Synthesis of STFT?
I'm studying Short-time Fourier Transform and I learned that if you apply a windowing other than rectangular, you need to overlap the frames---for example, 50% overlap for Hamming family---to ...
0
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0answers
58 views
Synthesis of 75% Window Overlap Add method for Short-Time Fourier Transform (STFT)
I'm doing the overlap-add method for STFT and I quite understand the implementation if it's a 50% overlap (where I add the 2nd half of the previous frame to the 1st half of the current frame during ...
0
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0answers
36 views
Pandas resample.mean()
I have a question to all you filter experts out there. I have some engine data sampling irregularly at about 50Hz. Recently I've been downsampling via the Pandas resample().mean() method. Basically ...
1
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3answers
121 views
spectral leakage for integral number of periods
I'm attempting to understand spectral leakage and read the following quote on wikipedia:
Windowing a sinusoid causes spectral leakage, even if the sinusoid has an integer number of cycles within a ...
0
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0answers
42 views
How to applly Hanning window on S parameter results?
I am working on Time domain computation. I have S parameter results simulated, using these results I do the Inverse FFT to get results in time domain.
I want to filter/window results using Hanning ...
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 ...
2
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1answer
125 views
Does spectral leakage include negative frequencies?
When choosing a window function, window duration, and/or transmission frequency (assuming sampling rate satisfies Nyquist), one may want to understand what sort of spectral leakage would occur at a ...
0
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0answers
45 views
Why is the coherence function unity at all frequencies when only one reading is done?
Several papers on the internet states that the coherence function is unity for all frequencies if only one reading is done, and that the coherence function requires an average of two or more readings ...
3
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1answer
145 views
FFT strong signal in middle frequency bin
I've developed a radar that I'm using to determine the distance to remote objects. It uses a custom PCB with an onboard FPGA that performs the DSP algorithms. The data from it is then plotted on a ...
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1answer
45 views
Python window funtion implementation [closed]
Can you help me implement window functions in python?
I have to write functions for following windows:
rectangular
triangular
hamming
hanning
blackman
parzan
Thank you in advance
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1answer
80 views
When can a windowed cosine be considered band-limited signal?
I have an exam in the following days and i have no clue of what is the response to this question in the exam:
given this signal:
$$g(t) = H\left(t+\frac{T}{3}\right) f(t) - H\left(t-\frac{2T}{...
1
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1answer
143 views
Correctly scaling FFT of different lengths
I have been looking at using two FFTs of different lengths and displaying the output magnitudes on the same graph (a shorter length window for the higher frequencies, and a longer one for lower ...
0
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0answers
67 views
How to applying window function to get same result with pwelch in MATLAB
I'm trying to calculate the power spectral density (PSD) to analyze signal power. To do so, I wrote a MATLAB code with the great help of others and below is my code.
...
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1answer
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47 views
Magnitude attenuation by a filter
I have a filter, with coefficients given by
$$
W=\sin((2*\pi*2*F_f*k/F_s)/(2*\pi*2*F_f*k/F_s))*h[k]
$$, where $F_f$ is the filter reference frequency, $k$ runs from $-N/2$ to $N/2$ ($N$ is the order ...
2
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2answers
142 views
STFT on time varying signal with good time and frequency resolution
I am trying to determine the main frequency of a noisy signal that varies in frequency over time. Ideally I want to detect changes in the frequency as rapidly as possible - say 50Hz update rate, but I ...
3
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1answer
774 views
Why is the Hamming and Hanning window the most widely used for speech spectograms?
When taking the Short-Time Fourier Transform of the speech signal, windowing is applied to taper away the signal frame at both ends and mitigate introduced artifact at expense of the maximum ...
1
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1answer
138 views
Cosine window function & signal with nonzero mean
I'm using cosine window function of order $p$:
$$ f(t) = \frac{2^p (p!)^2}{(2 p!)} \left(1 + \cos(\pi t)\right)^p $$
for frequency identification in real signals with several frequency components.
...
