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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32 views

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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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). ...
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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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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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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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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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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 ...
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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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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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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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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 ...
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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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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 ...
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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 ...
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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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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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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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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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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 $T$ ...
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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!

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