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1500 questions
10
votes
2 answers
Phase Correlation - Poor Performance on Noisy/Blurred Images?
I have successfully tested 1D phase correlation algorithm to determine vertical shift between two synthetic images.
When I moved to real images, however, it is not able to detect translation at all (the peak is located at 0, which is wrong…
Libor
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10
votes
2 answers
FFT of size not a power of 2
My question is regarding the input size of a signal which is not a power of 2 and we have to take the fft of it. Some solutions say that suppose if we want to take the fft of 1800 we should zero pad it till the length of 2048 to make it power of 2…
D X
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10
votes
1 answer
Symmetry of real and imaginary parts in FFT
INPUT
x[0] = (0.00 + j 0.00)
x[1] = (1.00 + j 0.00)
x[2] = (2.00 + j 0.00)
x[3] = (3.00 + j 0.00)
x[4] = (4.00 + j 0.00)
x[5] = (5.00 + j 0.00)
x[6] = (6.00 + j 0.00)
x[7] = (7.00 + j 0.00)
x[8] = (8.00 + j 0.00)
x[9] = (9.00 + j 0.00)
x[10] = (0.00…
gpuguy
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10
votes
1 answer
What is the maximum output of an IIR filter?
I am implementing an IIR filter in an embedded device based on ARM. It is implemented as a cascaded biquad structure (series of second order filters put back to back). The filter can be considered stable as all the second order sections in the…
Simactricals
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10
votes
1 answer
What transform can I use to "zoom" in a specific portion of a signal's spectrum?
If I recall correctly, there is a variation of the DFT that can be used to analyze a specific band of the spectrum of a signal. How is it called?
Arrigo
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10
votes
2 answers
Kalman Filter on Sinusoidal Signal
Suppose a system follows this equation:
$$ x(t)=A \cos(\omega t + \phi)+\eta$$
where:
$\omega = 2\pi f $ and $\eta$ is a random error
using Extended Kalman Filter, how does estimated value $\hat{x}$ be?
unwantednoise
- 103
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10
votes
1 answer
Difference between 'conventional' and 'adaptive' beamformers?
This might be a terminology question but I am not sure.
Basically, what is the difference between conventional beamformers, and adaptive beamformers? I thought that all beamformers were inherently adaptive to some criteria, like minimization of…
Spacey
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10
votes
2 answers
Does the Wiener Filter Achieve the Cramer Rao Lower Bound (CRLB)?
I have been told (Wikipedia agrees) that the Wiener filter is optimal when signal and (additive) noise are WSS. Optimal in the sense that it minimizes the mean-square error.
The Cramér–Rao bound is the lower bound on the variance of an unbiased…
Fabian
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10
votes
3 answers
Deconvolution with noisy measurement of impulse response function
I observe a noisy complex-valued signal that has passed through some linear time-invariant filter:
$$y(t) = (h * x)(t) + n(t)$$
where $h(t)$ is a causal and finite impulse response, and $n(t)$ is additive Gaussian white noise, $n \sim…
XYZT
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10
votes
1 answer
How do I implement an adaptive thresholding algorithm for underwater sonar
I want to implement an adaptive thresholding algorithm in MATLAB for filtering data received by an underwater sonar receiver. The data received has an interactive noise component resulting from underwater noise and specular reflection. CFARD method…
Saurabh
- 101
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10
votes
1 answer
What is the antialiasing algorithm employed by video cards?
What is the algorithm employed by video cards when one talks about for example 8xAA?
I thought the algorithm was about looking at neighboring pixels for correction. Yet, I hear that the implementation is just upsampling followed by downsampling.
m33lky
- 333
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10
votes
3 answers
the relationship between bandwidth and the datarate
One Question of my note is like this.
Consider a communication channel with a bandwidth of 2400Hz. If QPSK technique is
used, what is the possible transmission rate? (Assume that rectangular
pulses are used in the baseband signals, and that 90%…
Samuel
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10
votes
2 answers
What is this sinc doing in my LP-turned-HP filter output?
I'm trying to HP-filter a signal by LP-filtering it and subtracting the output from the original filter. To obtain the LP-filtered signal, I backward-forward filtered using a third-order Butterworth filter for a 16,000-sample signal. The cutoff…
Andreas
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10
votes
2 answers
Why does this manual bilinear transformation yield different results from Matlab's?
I've got a first-order Butterworth filter with the cutoff frequency $\omega_c$. Its transfer function is then
$$H(s) = \frac{\omega_c}{s+\omega_c}$$
Using the bilinear transform to find an $H(z)$ (what is that function called?), I…
Andreas
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10
votes
6 answers
How to do FFT fractional time delay (SOLVED)
I am trying to time-shift a signal using the FFT, however I have encountered some strange effects that depend on the size of the time-shift. I need to be able to shift the time by an arbitrary amount - i.e. floating-point time. I am using the method…
Axemaster
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