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1500 questions
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Why is the null of an adaptive beamformer narrower than antenna beam-width?
Question for those familiar with adaptive beamforming: Why is the null formed by an adaptive beamformer much narrower than the beamwidth of the antenna array?
Concrete Example
Suppose we have a simple uniform linear array (ULA). We can combine the…
Gillespie
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7
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Downsample a signal by a non-integer factor
I have a signal with a sample rate of 8.9286 MHz and I want to downsample it to 500 kHz.
Since 8.9286 is not an integer multiple of 0.5 I can't simply decimate. Which downsample techniques are recommended to be used?
If I use this solution then I…
Ivo Tebexreni
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7
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Can I "reverse" spectral leakage by solving a linear system?
When I compute a spectrogram of (say) a piece of music, there is a lot of frequency "smearing." Often we can reasonably expect that the "true" generating process is much sparser in frequency (i.e. maybe 10-20 active frequencies instead of…
Michael Kayser
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Avoid circular convolution aliasing in weighted overlap-add (WOLA) method
This link gives the procedure of implementing the WOLA method. It can be summarized briefly as windowing the extractd data frame, FFT, modify the spectrum, IFFT and overlap-add the windowed IFFT result to the reconstructed data buffer.
Suppose the…
ecook
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7
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How to exclude diffuse moving features in a stack of images
I have some stack of grayscale reconstructed images represented as a 3-dimensional matrix DPC with dimensions [Nz,Nx,Nt]. A single page/frame/image would be an NxMx1 slice of DPC. Each frame has some diffuse artifacts spread out over the image…
drakon101
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7
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5 answers
BandPass Signal Vs PassBand Signal
Am reading Rick Lyons - Understanding DSP book about Sampling. I have few doubts related to this chapter.
what is the difference between Bandpass Signal and a Passband Signal ?
Can somebody give an example for a Bandpass system which produces…
rajez79
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7
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1 answer
MUSIC Algorithm for Direction of Arrival (DOA) in Acoustic Signals
I have seen multiple reviews of the MUSIC algorithm for the estimation of DOA. Most of those reviews consider a complex signal input with a complex steering vector. So, how do I implement this algorithm in case I have an array of real…
Gideon Genadi Kogan
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7
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2 answers
A Machine Learning Based Algorithm as an Alternative to the Matched Filter
Consider we have to detect a known signal added with Gaussian noise. In this scenario, the matched filter is known to be an optimal filter for SNR. The question: is there any machine learning algorithm/tool that can be used instead of matched…
Creator
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4 answers
Find the Transfer Function from Magnitude and Phase Response
We can use common algorithms such as what is available in firls and firpm in MATLAB for least squares or minimax fitting to target magnitudes at given frequencies. I am familiar with the "Frequency Sampling" method to determine the filter…
Dan Boschen
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7
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What is $F(0)$ is "dc" component in the context of image processing?
It has always been said that $F(0)$ is the "DC component" in fourier transform. However, I don't get what it means to say that $F(0)$ is "DC" in the context of image processing.
The zero in this case just meant zero frequency, and hence no changes…
xenon
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7
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1 answer
How to turn Morlet wavelet into second generation wavelet?
I have a very specific application which requires to use the complex Morlet wavelet (or Gabor wavelet, if that's the name you use). I currently use the convolution theorem to compute wavelets transforms, but I'm reading everywhere that direct…
PhilMacKay
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7
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1 answer
In image processing, what is the difference or relationship between noise and artifact?
I would like to know the theoretical difference or relationship between noise and artifact in images, I barely know the relation between noise and distributions, but I'd like a deep explanation if it is possible related to medical imaging field.
Do…
omar
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7
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1 answer
Can the Walsh Hadamard transform be computed for non power of 2 sizes?
Can the walsh hadamard transform be calculated for odd image block sizes such as 5x5 or 7x7? Most of the examples I've seen are for 4x4 and 8x8?
I fear it probably can't from the description I read on Wikipedia ( though I'm still trying to fully…
trican
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7
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1 answer
Computing a convolution using FFT and more than minimum number of samples
Assume vector s is a set of time samples of length 1000.
Assume vector h is a set of samples of length 50.
If I want to compute the convolution of those vectors, the result will be 1000+50-1 = 1049 points long, as expected.
If I want instead to…
Jonathan Williams
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7
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7 answers
Qualitative Explanation of Fourier Transform
I am reading the book Fundamentals of Music Processing by M.Muller and I am close to understanding the idea behind the decomposition of a signal into basic frequencies, and would appreciate some help bridging a big gap in my understanding.
Fourier…
nikos
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