Questions tagged [window-functions]
In signal processing, a window function is a mathematical function that is zero-valued outside of some chosen interval.
220
questions
2
votes
1answer
86 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
votes
0answers
23 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 ...
2
votes
0answers
87 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 ...
-3
votes
1answer
36 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
0
votes
1answer
48 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:
$$g(t) = H\left(t+\frac{T}{3}\right) f(t) - H\left(t-\frac{2T}{...
0
votes
1answer
49 views
Correctly scaling FFT of different lengths
I have been looking at using two FFTs of different lengths and displaying the output magnitudes on the same graph (a shorter length window for the higher frequencies, and a longer one for lower ...
0
votes
0answers
20 views
How to applying window function to get same result with pwelch in MATLAB
I'm trying to calculate the power spectral density (PSD) to analyze signal power. To do so, I wrote a MATLAB code with the great help of others and below is my code.
...
1
vote
1answer
140 views
0
votes
0answers
61 views
Can Kaiser's formula be used to estimate the filter length of an FIR filter for all windowing methods?
I came across this problem while designing a FIR filter for given $\omega_p = 0.4\pi$ and $\omega_s = 0.6\pi$ along with the minimum stop-band attenuation $\delta_s$.
I have worked out some examples ...
0
votes
0answers
39 views
Magnitude attenuation by a filter
I have a filter, with coefficients given by W=sin((2*pi*2*Ff*k/Fs)/(2*pi*2*Ff*k/Fs))*h(k), where Ff is the filter reference frequency, k runs from -N/2 to N/2 (N is the order of the filter), Fs is the ...
2
votes
2answers
87 views
STFT on time varying signal with good time and frequency resolution
I am trying to determine the main frequency of a noisy signal that varies in frequency over time. Ideally I want to detect changes in the frequency as rapidly as possible - say 50Hz update rate, but I ...
2
votes
1answer
130 views
Why is the Hamming and Hanning window the most widely used for speech spectograms?
When taking the Short-Time Fourier Transform of the speech signal, windowing is applied to taper away the signal frame at both ends and mitigate introduced artifact at expense of the maximum ...
1
vote
1answer
72 views
Cosine window function & signal with nonzero mean
I'm using cosine window function of order $p$:
$$ 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.
...
0
votes
1answer
84 views
Can the Hanning Window be represented in the time domain
I know the Hanning window, $w_{Hann}(n) = 1 - \cos \left(2\pi \frac{n}{N} \right)$, is typically applied to discrete Fourier transforms. $N$ being the total number of points in a transient signal that ...
0
votes
0answers
36 views
Window function correction when using frequency domain likelihood
I was wondering if someone could tell me or point to resources which discuss what kind of of windowing corrections factors one should use when using a frequency domain Whittle likelihood for spectral ...
0
votes
1answer
355 views
Comparison of results own implementation and python signal.welch
I am trying to replicate the output of Python's signal.welch function to make an estimate of the PSD from an FFT calculation. I don't want to use the built-in function to understand better what is ...
0
votes
2answers
60 views
How can I graph the amplitude for a given frequency window over time?
I have simple audio files of single plucked notes from a guitar:
I want to graph the amplitude of each partials over time, rather than just have this color-coded "dB" intensity graphing I have here.
...
2
votes
2answers
101 views
How exactly does one apply a Hanning Window for a spectral estimate?
PREAMBLE
I am a graduate student researching evolutionary ecology. My supervisor and I have been trying to learn how to simulate colored noise, discretely, by the $\frac{1}{f^\alpha}$ power law for $\...
1
vote
3answers
99 views
How does a rectangular window affect the signal?
If i am not mistaken a rectangular window of length 10 gives us an array of 10x1:
1 1 1 1 1 1 1 1 1 1
And if we apply this to a signal we are left with exactly ...
0
votes
0answers
33 views
How to relate power spectral density with the number of resource blocks in LTE?
I am running a simulation with 100 Resource blocks for LTE OFDM and I plotted a PSD for it. Now I am able to bring down the out of band emissions when I perform an algorithm on it. Based on the ...
2
votes
1answer
703 views
Hanning and Hamming Window
I am new in the field of signal processing. What's the different between Hamming and Hanning window? When we use the former and latter?
2
votes
1answer
166 views
Purpose of multiplying fft output by Hann window?
I'm working with some acoustic propagation models at the moment.
A feature I've noticed in 2 of these models is that the output of the model is often multiplied by a Hann window in the frequency ...
4
votes
1answer
56 views
Amplitude Estimating Using a Windowed DFT
Let's say we want to estimate the amplitude A of a mono-frequent signal using a windowed DFT. The frequency of the signal is unknown, and the frequency resolution of the DFT is limited, thus it cannot ...
0
votes
1answer
38 views
Why does shortening window widen its Fourier Transform?
On page 76 of the book Discrete Time Speech Signal Processing by Thomas F.Quatieri, the author states "shortening the window widens its Fourier Transform".
Can anyone explain why?
0
votes
0answers
46 views
Attempting to remove the 60Hz frequency out of a noisy ECG signal
load eeg_plus_noise
Fs=200;
Fn=Fs/2;
b = fir1(64,[59.8 60.2]/Fn,'stop');
figure(3)
freqz(b,1,512,Fs);
y = filter(b,1,eeg_plus_noise);
I am then using the ...
0
votes
0answers
71 views
Windowing in frequency domain. how to cut a spectrum using window function in frequency domain?
I have a set of measurement data of a FMCW radar and trying to estimate the system transfer function. In the frequency spectrum, I can see multiple peaks due to the non-linearity that exist in the ...
1
vote
1answer
46 views
Quantized error in scatter plots for a hamming windowed LTE signal
I have a time domain signal based on LTE standards.
Carrier spacing = 15KHz, Symbols per slot = 6, extended Cyclic Prefix = 512 samples
FFT size = 2048, No. of sub carriers = 1200, channel BW = 20MHz, ...
1
vote
2answers
145 views
What version of sinc function to use ? (With additional factor of $\pi$ or not.)
I have an exam tomorrow on Signal Processing and one of the questions can go two ways:
Use a Hamming window to design an Nth
th order (N+1 tap) band pass FIR filter with a pass-band
between $f_0$-$...
0
votes
1answer
48 views
I have the scatter plots for a Hamm and Tukey(0.25) windowed data. The complex data plotted from Hamm windowed forms a pattern, why?
The Hamm windowed complex data forms some sort of a quantized pattern whereas in the same code if tukeywin(0.25) is applied normal noise is observed. Any idea why ?
0
votes
1answer
45 views
How to window a time domain signal for 6 symbols with cyclic prefix length of 512 samples?
Based on LTE stds. I am running a simulation for 6 symbols (each having 1200 central subcarriers) each in a 2048 FFT/IFFT bin. To these symbols are appended 512 samples as cyclic prefixes. I have to ...
-1
votes
1answer
39 views
Applying window function to reduce out of band emission for a symbol in LTE simulation?
I have to apply a window to an IFFT'ed signal (based on LTE standards, simulated for 1 symbol - 100 resource blocks - 1200 subcarriers). I have a signal which I have simulated till the IFFT. Now I ...
0
votes
1answer
218 views
Overlap/add time-domain audio frames: How does normalization/scaling work with overlap greater than 50%?
I am attempting to overlap-add time-domain audio frames in a real-time context (with a continuous stream of data coming-in). Each frames consist of 1024 samples and have been previously "Hann" ...
1
vote
0answers
49 views
Frequency bins too powerful at the start and at the end of each sample computed DFT data
I've taken the following link http://coding-geek.com/how-shazam-works/#comments as a project to start practising and learning signal processing and python programming for me to get started in speech ...
1
vote
1answer
219 views
Modified Periodogram function in MATLAB
Given below is a function written in MATLAB for computing the modified periodogram, taken from Hayes, Statistical Digital Signal Processing and Modeling
...
-1
votes
2answers
99 views
Attenuate frequency bin in FFT array resulting in artifacts [duplicate]
Am trying to remove noise for certain frequency bands by attenuating freqeuncy bins in the FFT array. However this results in artifacts to be formed, where there are clicking sounds in between each ...
0
votes
2answers
257 views
Window length in matplotlib's specgram
In the paper about speaker verification I can read that
Two quantities have
to be set: the length of the window and the shift between two
consecutive windows. For the length of the window, two ...
1
vote
1answer
730 views
Seven term Blackman Harris window
I am currently trying to evaluate a high resolution ADC for which I need to window my output data for the FFT. Up until now I have been using the default 4 term Blackman harris window in MATLAB. ...
1
vote
3answers
96 views
how could window function really suppress those frequencies that we don't want?
I know we can use window function to decrease leakage phenomenon by making the end of a non-periodic signal to be zero at both end, so that to make it like "continuous and periodic" when doing fft.
...
1
vote
2answers
414 views
Linear Convolution in DSP and Hann window
My understanding is that when dealing with discrete finite sequences, convolution done thru FFT is circular. To obtain linear convolution, one would pad the input with zeros up some appropriate length....
1
vote
1answer
3k views
How to calculate the power of a discrete signal? / Clarification on PSD estimates
I want to calculate the channel power $ P_\mathrm{x}$ of a given discrete and complex signal $x[n]$ (with a length of N) in a given bandwidth $B$.
I'm aware, that I could probably apply a sharp ...
0
votes
1answer
324 views
Windowing a signal for FFT
I am actually working on a project involving the cross-correlation of two signals. My cross-correlation code is working fine, but I suspect that I should apply a window to my data set in order to ...
0
votes
1answer
73 views
Difference between applying a window to a whole signal and frames.
I'm going to do feature extraction using a speech signal.
The first step is the windowing of the signal using Hamming window.
I'd like to know if I should apply one single window to the whole ...
1
vote
1answer
271 views
Apply windowing before FFT or after?
I am computing a spectrogram and I've found a code example online which goes like this:
...
1
vote
1answer
65 views
Why is the raised cosine pulse for digital communications so popular?
The raised cosine pulse is essentially a windowed sinc function, designed with some roll-off in mind. Why do we use this particular window, as opposed to other windows such as Hann, Hamming, Kaiser, ...
1
vote
1answer
988 views
Why square-root of Hanning Window
I just studied an implementation (Matlab) of a windowed FFT and saw the following line of code:
w = sqrt(hann(fft_length, 'periodic'))
and later:
...
0
votes
1answer
65 views
Getting a weired behavior when windowing an audio signal
I am processing audio signals using Essentia, an open-source library and tools for audio and music analysis, description and synthesis.
Here is a waveform corresponding to a frame extracted from an ...
5
votes
5answers
984 views
Does windowing affect Parseval's theorem?
I have computed Fourier transform from ecg data.It does obey Parseval's theorem,
relation
$$\sum_{n=0}^{N-1} \Big| x[n] \Big|^2 = \frac{1}{N} \sum_{k=0}^{N-1} \Big| X[k] \Big|^2$$
is fulfiled. ...
0
votes
1answer
514 views
Probability of False Alarm versus SNR
I'm currently testing the performance of an energy detector using two tests. One test involves finding the optimal threshold to achieve a probability of detection(Pd) of 0.9 and a probability of false ...
1
vote
3answers
4k views
Window period(overlap) and FFT
How does changing the window period (i.e the number of points overlap between two frames) affect the FFT results ?
Suppose that a time series signal was converted to frequency domain by FFT with ...
0
votes
1answer
262 views
fft - spectral leakage from noise into target frequency?
I have an acoustic setup. A sender, emitting a clean sine signal. The receiver is far away. In the time domain, the sine is hardly visible because the noise is nearly as big as the signal. In the ...
