lxg
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What is the difference between continuous, discrete, analog and digital signal?
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8 votes

A signal is indeed a function. Given a signal $f(x)$, according to whether continuous or discrete for both the variable $x$ and the function $f(x)$, there are four types of combinations: (1) $\mathbf{...

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Why DTFT coefficients are periodic and why continuous Fourier transform coefficients are not periodic?
4 votes

The explanation by @Maximilian Matthé is a standard and formal approach for this question. But I think it is not intuitive and easy to understand the reason. In the following, I will try to explain ...

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How can I tell if an image is part of another image?
4 votes

This problem can be treated as signal/image detection or image registration. From the image registration perspective, there is a good tutorial that is exactly what you need: Registering an Image Using ...

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Signals and systems : why do we study causal signals?
2 votes

I think the "causal signal" is simply borrowed from the "causal system". For a system, the "causal" constrain is meaningful and fundamental, i.e., if the input does not occur, the system should not ...

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shifting and reversing the signal
2 votes

all changes are performed on the variable $n$, thus for $x[3-n]$, we can treat from two approaches: (1) $x[n]$ shifts to $x[n+3]$, and then reverts to $x[-n+3]$ (2) $x[n]$ firstly reverts to $x[-n]$,...

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Matlab FFT not producing symmetric spectrum
1 votes

Please check the type of "pulse". Is it a real type or complex type? I do not know what your "rcosdesign()" looks like, and I used "pulse = rand(1,99)" and got:

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How is Bayesian Estimation related to filtering?
1 votes

For linear filtering, it can always be interpreted in the frequency domain, thus, it is impossible to discard the noise without affecting the signal in the same frequency position. For the Wiener ...

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Practical advices for applying phase correlation in image registration task
1 votes

For blurred images, for which I mean the blur kernels are different for the two images, the PC algorithm can also be extended to handle this case. Please refer to: PEDONE M, FLUSSER J, HEIKKILA J. ...

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How do multirate systems introduce 'efficiency' in computation?
Accepted answer
1 votes

I will try to explain from my understanding. For interpolation, the whole process can be viewed as two parts: up-samping with padding zeros, and the low-pass filtering. The zero padding will increase ...

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Image Processing and applicability of 2D Fourier Transform
1 votes

First of all, the image is a 2-D function, e.g., f(x,y). Then, if you could not represent it as a separable form, e.g., f(x,y) = f1(x) * f2(y), you could not say that a given row will not affect other ...

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2D Fourier Transform of Rotated Discrete Domain Signal
1 votes

The Rotation Property means that the choice of coordinate direction would not affect the spectrum of the signal itself. To perform the rotation, I think it is better to do in the spatial domain since ...

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Phase Correlation and Negative Shifts
1 votes

the matter is due to this one: product = ft1[p] * conj(ft2[p]) You can change to: product = ft2[p] * conj(ft1[p]) I guess input1 is the reference image.

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When is phase needed in DFT?
1 votes

From the perspective of filtering, a common LTI system will weight each components in the input signal: (1) weighting means changing the magnitude values (it is apparent in multiplication of two ...

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100 kHz sinewave contaminating a signal sampled at 48 kHz
1 votes

In your case, since 100kHz is more than twice 48 kHz, it will be folded twice in the sampled version, then there are two pairs of positions: +/-4 KHz and +/- 44Khz.

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Why does the term "discrete" usually appear near the term "digital?"
0 votes

Theoretically, it is easy to analyze a discrete signal only in variable. A digital signal is discrete in both variable and value, which is the case in practical digital processing systems, such as DSP/...

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Determine when a constant signal changes to another constant value
0 votes

In your example, 255 255 255 255 255 210 180 170 140 130 130 130 130 130 130 it seems that there is no noise but just the transition between the jump. That is, if noise does exist, there will be ...

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Why is the dB plot of a signal usually non-positive?
0 votes

The dB is a ratio, thus a reference is needed. A negative dB value means the signal level is less than the reference value. Note that the signal-to-noise (SNR) always uses the dB format, but the dB is ...

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Why do we always characterize a LTI system by its impulse response?
0 votes

The impulse response, the step response, and the frequency response all come from the "linear" nature of a LTI system. Therefore, which one is preferred is actually determined by which decomposition ...

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Binarization of image for varying background and foreground colors for OCR
0 votes

please refer to this article: Adaptive thresholding for binarization

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DFT Frequency domain analysis and interpolation
0 votes

(1) I think the first question is indeed why the digital frequency is periodic. For this matter, it can be checked on the definition of the DFT but it is not intuitive about the reason. To understand ...

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What are the differences between estimation and detection optimal filters (matched and Wiener)?
0 votes

For my understanding, detection is to judge whether a known signal presents in the unknown signal, and the matched filter is indeed the reversal version of known signal itself, thus the matched ...

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Log-Polar DFT Based Scale-Invariant Image Registration
0 votes

I guess it is due to specific implementation issues. For example, (1) it is better to perform the windowing pre-processing before the DFT; (2) you can check the Highpass() function, and you can refer ...

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