Signal Processing Stack Exchange
Signal Processing Stack Exchange

Questions tagged [signal-analysis]

The processing of signals for the purpose of extracting a parameter or property embedded in a signal. Signal goes in and far fewer numbers come out.

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I and Q components and the difference between QPSK and 4QAM

Both 4QAM and QPSK apparently produce the same waveform, but are they the same mathematically? In a QPSK constellation, are the mapping points at 45, 135, 225 and 315 degrees while the 4QAM is at 0, 90, 180 and 270? I also struggle to understand the…
chwi
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Why complex numbers are represents as a+ib and can't be as (a,b)?

I am confused as why do we need to represent the complex numbers with the imaginary y-axis if we can simply represent them as (x,y) ? I've read that Multiplication by i is an anti-clockwise rotation of a quarter-circle over y-axis. Multiplying 1 by…
Sufiyan Ghori
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How to check if a signal is power signal or energy signal?

What is the procedure to check the signal type? example: $ x(t) = A \sin (\omega t) $ $ y(t) = A e^ {-\lambda |t|} $
Giannis Foulidis
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What's the noise in this signal ? (Beginner question)

There is this raw ECG signal that I have obtained its frequency content in Matlab. The signal was sampled at 600Hz. The following is signal and the frequency content. I want to know what the interferences are. I'm very new to DSP, and I feel like…
BigRedMachine
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Question on understanding the time-bandwidth of a signal

I read from a paper (Ozaktas, H.M., et al. (1996) Digital Computation of the Fractional Fourier Transform) that says The time-bandwidth product can be crudely defined as the product of the temporal extent of the signal and its (double-sided)…
ecook
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Periodicity of the output of causal time-invariant systems when the input is periodic

For time-invariant systems, if the input is periodic, the we can argue that the output is periodic: If we shift the input signal one period, we come up with the same signal as before, and since the output must be shifted the same amount as a result…
user215721
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Finding the maximum of a real valued trigonometric polynomial

I have been posting all over SE looking for a good method of finding the maximum of a trigonometric polynomial. A trigonometric polynomial is the sum of a set of sinusoids, $$a_0 + \sum_{k = 1}^{N} a_k \cos(k \theta + \phi_k)$$ and can also be…
geometrikal
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What are the restrictions on DFT input sequences in order to produce valid spectral results

In a recent comment (as I understand it) our colleague OverLordGoldDragon’s stated that the only restrictions on DFT input sequences, to produce valid DFT spectral results, are that (1) the input sample values must be finite in amplitude and (2)…
Richard Lyons
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The meaning of $k \delta (t)$

Reading the signal literature I often come across the expression $k \delta (t)$ where $k$ is a constant. I presume this is a notation to suggest we are referring to the area or strength of the Dirac function since the multiplication of a constant,…
rhody
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Feature extraction from spectrum to aid categorisation

i have two sets of signals whose spectrum looks like shown in the figure. The first column of signals belongs to category 1 and the second belongs to category 2. Looking at the spectrums I want to identify features which will differentiate the…
Dhruv Nigam
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Difference between AoA and DoA

I noticed a mixed usage of AoA (Angle Of Arrival) and DoA (Direction Of Arrival) and was quite confused about the exact distinction between AoA and DoA with respect to wireless signals. Reference to any document for further understanding will be…
niil87
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Could these be two peaks?

I'm looking at heart rate variability (HRV). Frequently, in the Fourier transform I see two peaks that are close together. How could I determine whether this is two peaks, or just one peak and noise? Please see figure below. The units of the x…
Chris
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What does the term "railed" mean in signal processing?

I'm having trouble finding a definition of "railed" that relates to signal processing. Am I correct in my guess that this term is in fact from this field? My signal data comes from an EEG device. The lightly documented open source software I'm using…
Hack-R
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Is there a problem with using the WAV format for non-audio signals?

I have biological signals sampled at 1 kHz. The signals tend to behave fairly simply, sinusoidally. The software I've used to collect these data uses their proprietary format (*.adicht) and so I have to export to something I can work with in MATLAB,…
stck8888
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Variance of deterministic sine wave

I have read that variance of a deterministic signal is 0 because it is deterministic and does not vary over time. In this explanation, I am considering a $\sin(t)$ wave where value at each t is a variable(it will be a random variable when we are…
Pranav Prakash
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