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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questions
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lopsided Hanning Window function
I am processing sensor signals and have been looking at using window functions to smooth out the signal before I conduct a fft on it. A normal symmetrical hanning function seems to disorientate the ...
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1answer
31 views
Graph Plot On Time Shift of Cosine Signal Hanning Function
I am plotting time shift of the Hanning function. I find few plot result that I am not able to understand. Therefore I would like to ask my question here. The given Hanning function is:
$$
x(t)={\tt ...
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1answer
51 views
Under which conditions will windowing with a rectangular window intime always lead oscillations in the spectrum?
I'm going through some conceptual questions about windowing signals. I came across the following:
Assume a sinusoidal signal - under which conditions will windowing with a rectangular window ...
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2answers
65 views
Direct calculation of the fft of a rectangular window
For a rectangular window defined as,
the frequency spectrum equation and magnitude (or pseudo-magnitude) plot are,
However, when I apply Scilab's fft() function or the definition of DFT definition ...
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1answer
73 views
Window with optimal sidelobes for a given ENBW / frequency-resolution
Is there a family of windows which is "optimal" in terms of energy above/below a boundary, but with controllable ENBW/bandwidth? By optimal, I mean maximising energy concentration inside ...
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1answer
38 views
sensor data windowing and normalization
I am getting up to speed with working with sensor accelerometer data. I am looking to conduct a FFT on this signal. I found that the signal being non periodic is causing issues so I have tried to look ...
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1answer
59 views
Plot of the Fourier transform of the Sine Window
In Wikipedia, a Fourier transform of the Sine Window
\begin{align}
w[n] = \sin \left(\frac{\pi n}{N} \right), \ 0\leq n \leq N
\end{align}
is plotted like below. However, I am not sure how to obtain ...
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1answer
202 views
Do we guess the cut off frequency when passband edge frequency and stop band edge frequency are given? FIR Filter design-LOW PASS FILTER
Say passband edge frequency=0.25 $\pi$
Stopband edge frequency=0.35 $\pi$
What is the cut off frequency? Do we average these 2 frequencies and write the answer or what is the procedure to find cut off ...
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2answers
50 views
Calculating Hann WIndow
Hey I have this CSV file which contains 8 chunks of 256 samples of a sine wave with different frequencies (each chunk has different frequency starting from 8 to 64Hz).
The total samples of this file ...
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35 views
What is the effect on the cross-correlation of two windowed signals?
I've been trying to determine the effect of performing the cross-correlation operator on two windows signals.
For example: suppose we have two Sinc functions. The Sinc function is defined as $\frac{...
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1answer
49 views
Faster way to Implement a CFAR (window average) Threshold
I implemented a version of a CFAR average in MATLAB but it's 'slow' and I need to speed it up. I included the pseudo code and logic below. I used a nested for loop to calculate the moving average but ...
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1answer
50 views
Mitigating high-frequencies after sampling
I have a dummy signal that I am sampling at $T = 100 \ \mu s$. According to the Nyquist frequency, I can identify frequencies up to $\pi/T = 31416 \ rad/s$, as we can see in the FFT of my signal (blue ...
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1answer
91 views
Biorthogonal Windows
I am starting to study about the concept of biorthogonal windows and the relation to (Discrete) Fourier transform and short-time Fourier transform (STFT).
I have not found an introductionary review of ...
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1answer
55 views
Basic Question about Windowing in DTFT
I was reading this and it explains the various windows such as Rectangular, Bartlett, Hanning, Hamming, and Blackman. Specifically, I saw this graph comparison of their dB magnitude frequency response ...
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1answer
69 views
Integral of Kaiser window
I want to sample (evaluate at regular intervals) the integral of the Kaiser window.
Is there a nice closed-form solution to this, so I don't have to do it numerically?
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49 views
Running window design for irregular or nonuniform time series
I have to deal with multiple time series $X_n$ that are non-uniformly or irregularly sampled at increasing times $\Theta=\{t_k\}_{k\in \mathbb{Z}}$ ($ t_k<t_{k+1}$). In case this could help, this ...
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1answer
31 views
Confusion understanding phase shift/delay?
I am reading proakis, as shown highlighted in attached snap shot,there is '-'sign along with j,but still it is written (underlined red) implies shift in positive n direction,why and how positive?when ...
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114 views
Determining SINAD from measured data
I would like to determine the SINAD of a distorted signal from a measurement and have troubles to get consistent data. The problem is (at least to my understanding) that I only have a very limited ...
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2answers
149 views
Why does Matlab spectrogram look stripy when windowed input is zero-padded?
I am working on a little project, and stumpled upon something I cannot understand yet. I am learning cognitive science, and don't have DSP knowledge background, only learning from what I find on the ...
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0answers
38 views
Periodogram/PSD from FFT amplitude
I have performed a STFT for signals and obtained the amplitude through
...
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2answers
56 views
FFT/PSD/IFFT analysis on single axis piezoelectric accelerometer signals for curb impacts
I'm trying to denoise the signal by performing PSD analysis and followed by IFFT. Ultimately, I want to generate Force and Displacement plots from the denoised acceleration signal.
Noisy Acceleration ...
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2answers
175 views
Windowing of signal before FFT
I am facing an interesting problem: I have a signal in the time domain. In order to avoid discontinuities at the edges of the signal --- which would lead to artifacts when calculating the FFT --- I ...
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114 views
How to determine number of filters in filter bank based on spectrogram of audio signal?
I want to do an analysis and than synthesis of audio signal, which is audio of vowel 'a', using Matlab. For this I need to use filter bank(array of band-pass filters). I have drawn four different ...
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61 views
Blackman window magnitude attenuation
I am trying to compute the fundamental phasor using sliding window DFT. I have employed a Blackman window in conjunction i.e
$$
\sum_{k=0}^{L_{DFT}-1}x(k) w(k) e^{-j2\pi k/N}
$$
where $x(k)$ is the ...
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3answers
122 views
What's the ideal FFT window for measuring a group of signals of differing amplitudes but close in frequency?
In my system, I need to measure the amplitudes and phases of four lasers, each of a different, known wavelength, chopped at a 50% duty cycle via TTL at frequencies spaced evenly (or not) around some ...
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1answer
66 views
Find Magnitude of a DFT signal using a Blackman window
Hi I've been given a signal made of a series of cosines. I have taken the DFT of the signal using a rectangular window (blue), hamming window (red) and a Blackman window (black). I have identified two ...
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1answer
66 views
Understanding this Hanning Window implemented in microcontroller
I'm trying to calculate RMS of an AC signal which input frequency may vary from 40 to 70 Hz. I would like to use a window function because it accounts for frequency variations and also my ADC sampling ...
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2answers
63 views
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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1answer
82 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).
...
5
votes
1answer
217 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
139 views
Estimate Parameters of Linear Combination of Harmonic Signals with Partial Known Frequencies
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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49 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 ...
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2answers
63 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
39 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
49 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
388 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
119 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
351 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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1answer
258 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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1answer
224 views
Confusions in windows based design of FIR filters?
I am reading the proakis book"DSP USING MATLAB 3rd Edition"
In chap 7, article 7.3, i came across example 7.8,where i saw formulas for pass band ripple and stop band attenuation
I have ...
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3answers
128 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
votes
1answer
243 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 ...
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1answer
557 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
120 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
166 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\...
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1answer
329 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.
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1answer
56 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 ...
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1answer
37 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.
2
votes
2answers
394 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
309 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!
