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1500 questions
9
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2 answers
How to apply a filter kernel
A filter that can be used for digital signals like audio, video or image processing can be defined using a matrix ("kernel") that weights the surrounding area (this is a description I read in lecture notes from someone else).
The…
muffel
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9
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1 answer
Real time slope and peak detection and calculation
I have a signal that I sample at 500khz. I am trying to detect a rise, fall and the peak in the incoming data. The base of the peak could be for 250 usec or 2.5msec, amplitude could be 6db or 15db above the noise floor. I don't have good snr…
Ktuncer
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9
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2 answers
Spectrum of FSK signal
I have implemented a simple V.23-like FSK modem in C here.
The peculiarity of the chosen modulation is such that 0's and 1's are sent as tones of two different frequencies (2100 Hz and 1300 Hz respectively) and the duration of each symbol is…
Alexey Frunze
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9
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1 answer
Number of Daubechies coefficients
I am wondering about the correlation between input size and number of coefficients given by a discrete wavelet transform.
I am using Daubechies wavelets to describe a 1D function and I'm using PyWavelets to implement it (which is analogous to the…
Gustav Larsson
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9
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1 answer
Is autospectrum the same as power spectrum density?
In my slides about signal processing, there is one that mentions the same thing as the beginning of this and this answer, namely that the Fourier transform of a signal, squared is the power spectrum density of the signal.
In this talk, it is…
Mien
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9
votes
2 answers
Fast pitch recognition
I need to detect pitch (measure signal frequency) while the musicians play music, giving a warning if they are out of tune, but music happens to be a bit too fast for FFT (Fast Fourier Transform).
Below I try to give a technical description of the…
18446744073709551615
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9
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2 answers
What is the relation between the PSDs of filter input and output called? $R_Y = |H|^2R_X$
If a wide-sense stationary signal $X$ is fed to an LTI filter with the transfer function $H$, the power spectral density (PSD) of the output $Y$ can be expressed as:
$$R_Y(f) = \left|H(f)\right|^2R_X(f)$$
where $R_X$ denotes the PSD of $X$.
Does…
user42
9
votes
4 answers
About Fourier transform of periodic signal
In Fourier transform for periodic signal, I checked different books and I found a different explanation in each book. Let's take the explanation in Signals and Systems by Rajeshwari & Rao:
The resulting Fourier transform for a periodic signal…
Aadnan Farooq A
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9
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1 answer
Practicality of the assumption of i.i.d. for Rayleigh channels
I would like to understand how far the assumption of having i.i.d. is accurate/valid (from the practical point of view) when an OFDM system is working in Rayleigh channels. Is this means the channel has to encounter flat and slow fading? If not,…
Noor
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9
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2 answers
Detecting a Signal Inside a Time Series Using MATLAB's $ \tt xcorr() $
I would like to find the exact replica of signal A in time series B. I am working with the simple toy example below, in which A is located starting at the 4th position in B.
I thought that using xcorr would achieve this but I am clearly failing…
val
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9
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5 answers
Fields of math needed for digital filter design
I want learn digital filter design. My knowledge of math is at high school level. I can learn math through the Internet. Then, what fields of math do I have to learn?
George Theodosiou
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9
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1 answer
What is a "Hampel Filter" and how does it work?
One of the new functions in the MATLAB Signal Processing toolbox for R2015b is the Hampel Filter. It appears to be used for outlier removal and from the examples, it looks like it might do a better job than a median filter.
Unfortunately, as of yet…
Damien
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9
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2 answers
iPhone iOS UIImage how to detect a "laser pointer" dot on a camera feed?
I got a tracked robot toy and I'm controlling it with an iPhone. The robot outputs a live camera feed of a known frame size and I'm displaying it on UIImage.
I've added a laser pointer to the robot and fixed it alongside the axis of the robot. I'm…
Alex Stone
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9
votes
1 answer
Filter order estimation
Assume some unknown but small and finite number of poles and zeros in the complex Z plane, all with complex conjugates, producing some response. Strictly from the absolute value of a set of equally spaced points around the unit circle, say greater…
hotpaw2
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9
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3 answers
Significance of energy and power signals in real world
In signals and systems subject we study about calculating energy and power of a signal, but what is their practical significance.
Also what is the significance of a signal which is neither energy nor power signal ?
Patrick
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