Questions tagged [window]
The window tag has no usage guidance.
75
questions
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1answer
48 views
What does the 'B' parameter represent in Wikipedia's page on window functions?
I was trying to learn some more window functions and was referencing the Wikipedia article on the subject. I've noticed on a lot of the plots, there appears to be a capitalized and italicized letter B....
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1answer
453 views
MRI reconstruction using windowing based apodization
I am trying to apply windowing to do MRI reconstruction. I have a 256 point one dimensional k-space samples which look as follows:
Here, the real part(green) is flat around 0 and the blue curve is ...
0
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1answer
488 views
Integer and a half periods of sine wave in DFT window
Why does a pure sine wave starting and ending at 0 in the sample window of a DFT but containing 1.5 cycles (or periods) produce the same spectral leakage (i.e. not more) as a pure sine wave with ...
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2answers
165 views
Bandpass Filter Order vs Sample Numbers of Noisy Signal
I'm working on signal filtering in MATLAB. i wrote sample code that generate 50 Hz signal with some noisy frequency and use Kaiser bandpass filter to get only 50Hz frequency. this code work great! but ...
2
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1answer
162 views
How to Calculate the Hann Low Pass Filter / Kernel for Image Processing
I'm currently studying for an exam in image processing and stumbled upon a exercise which i could not answer and my professor will not be available before the exam anymore. The exercise goes as ...
4
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1answer
208 views
What is the LOW frequency resolution rule analogous to Nyquist?
If I'm analyzing a signal in the frequency domain, I know about the well known Nyquist criteria that the sample frequency must be > 2x of the highest component present in the signal.
However, there ...
0
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2answers
1k views
finding the fundamental frequency in frequency domain
I want to get the fundamental frequency of a signal. I used a time domain approach first. It just sums up the differences between the signal (lets say 2048 samples) and the delayed version of the same ...
1
vote
1answer
251 views
Design a FIR filter with a Kaiser window
Here is the exercise I am working on.
Use the window design method with the Kaiser window to design a linear phase high pass FIR filter of minimum order that meets the following specification:
$\...
6
votes
3answers
17k views
Moving average vs. Moving median
I have read in many places that Moving median is a bit better than Moving average for some applications, because it is less sensitive to outliers.
I wanted to test this assertion on real data, but I ...
0
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1answer
650 views
Why does the Hamming window attenuate the FFT?
I am working on a very simple voice recognition system using the msp430. In my research I've read that for real life audio signals its necessary to apply a window to the FFT data because the audio ...
1
vote
1answer
146 views
Non-separable, higher-order generalized cosine windows in 2D for images
Higher-order generalized cosine windows define a useful parametric family of windows functions, embedding Hamming, Hann, Blackman, Nutall, etc.:
$$w(n) = \sum_{k = 0}^{K} a_k\; \cos\left( \frac{2 \pi ...
1
vote
1answer
329 views
How is the ends of a bandpass filtered signal reliable after applying the cosine taper?
A taper function decaying to zero at ends such as a cosine window is routinely applied to the signal before bandpass filtering to reduce end effects. Obviously the window alters the waveform.
So, as ...
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1answer
940 views
How to Combine FFT Overlap Results?
We currently have C/C++ FFT code with Hann Window function support. For a large data (over 10,000) we want to split this into 1024 samples with 50% overlap. For each 1024 sample, we window and fft.
...
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1answer
137 views
Sensitiviy and Resolution in Windowing Functions
When I read the article Windowing Functions, there are two terms that are does not understanding them well, sensitiviy and resolution.
I looked for this two terms on the web, And I conclude that ...
0
votes
1answer
120 views
Subsampling data: terminology
I'm writing software and the data reporting frequency is slower than the acquisition cycle, so effectively sub-sampling is being done. Different data types require different methods of sub-sampling ...
0
votes
2answers
362 views
Fourier Synthesis With Varying Frequencies Over Time
I'm doing some fourier synthesis by making bins of complex numbers, filling them out with the amplitude and phase information and using IFFT to turn that into time domain samples.
I'm able to make ...
1
vote
2answers
412 views
Instantaneous magnitude
I was reading this thread: How to get Instantaneous Magnitude for a Instantaneous Frequency From FFT?
I have basically the same question, but I'm curious about more detail about the Hann window ...
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0answers
142 views
Band-pass filtering on whole signal or overlapping chunks?
I am working with a signal acquired by a pulse oximeter, i.e. a device that records the change of light intensity reflected by a specific tissue depending on its blood perfusion.
Since I am interest ...
0
votes
1answer
4k views
Reconstructing time domain signal with Hanning window
I am currently working on a frequency domain real-time application on a digital signal processor. Currently for one time frame of my algorithm I read in time domain data into a buffer, perform a ...
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1answer
473 views
FFT window corrupts signal
this is a newbie question.
My goal is to create audio filter that cleans human speech from noise. I started with learning all about fft filters. At first I've created simple fft filter with ...
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0answers
361 views
Welch's Overlapped Method
I am measuring wind speed using a number of different anemometers. These anemometers are placed on a structure which exhibits sinusoidal motion. Thus, the signal of the anemometers contains both the ...
0
votes
1answer
4k views
Overlapping with flat-top window MATLAB [closed]
I am applying a flat-top window to signal because I am very interested in its actual amplitude in the time-domain. I have read that overlapping will improve results. I am using MATLAB and the ...
0
votes
2answers
700 views
Why are window functions used when calculating spectral estimates, really?
Having just read the rather long article on Wikipedia about window functions, I still do not see the mathematical point in using window functions when calculating spectral estimates (using e.g. Welch'...
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1answer
378 views
Will using window in Welch's method introduce artificial peak in estimated PSD?
I'd like to estimate the power spectral density of the signal attached here, the sampling rate is 100 Hz.
If I don't do windowing (i.e., use boxcar window), the result seems to be a simple $1/f^2$ ...
1
vote
1answer
872 views
Additional prefix and suffix required when windowing an OFDM symbol?
To reduce out of band energy, it is common to apply a Raised Cosine filter to the front and back of an OFDM symbol. It is also common to overlap the windowed portions of adjacent symbols to eliminate ...
