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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2
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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 ...
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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 ...
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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 ...
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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
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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}{...
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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 ...
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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. ...
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1answer
140 views

windowed sinc filter in matlab

Hello i'm designing a low pass filter windowed sinc in matlab ...
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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 ...
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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 ...
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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
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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 ...
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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. ...
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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 ...
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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 ...
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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 ...
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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. ...
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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 $\...
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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 ...
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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 ...
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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
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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
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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 ...
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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?
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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 ...
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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 ...
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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, ...
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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 $f_0$-$...
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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 ?
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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 ...
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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
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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" ...
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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 ...
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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 ...
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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 ...
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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 ...
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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. ...
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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. ...
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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....
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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
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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
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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 ...
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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: ...
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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, ...
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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: ...
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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 ...
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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. ...
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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 ...
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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 ...
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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 ...