Questions tagged [discrete-signals]
A discrete signal or discrete-time signal is a time series consisting of a sequence of quantities.
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Questions about autocorrelation, correlation, and randomness
I'm learning about autocorrelation functions and trying to calculate some from a time series. Conceptually, what is the difference between the following two autocorrelation functions?
$$g_{1}(\tau)=\...
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40 views
Discrete and Continuous Signals
I am new to the signals area and have been reading through a lot and have some questions.
Suppose I have a saved audio file on my computer, .wav file. I can view the time domain of the signal by ...
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45 views
OFDM vs. V-OFDM channel equalization
I am trying to work on Vector OFDM (V-OFDM), but actually I had an issue when equalizing the channel !, I don't know why that issue happens.
Let me give a brief description to those who are not ...
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2answers
72 views
Getting the DTFT from the DFT samples
How would you get the DTFT from the DFT samples?
How will the DFT indexes map to the discrete frequency and what kind of an interpolation would be required?
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2answers
35 views
Confused in Smoothing a signal in the Frequency domain
First of all i am new in DSP, so i have no solid education in the field.
I have convert my time domain acceleration-seismic data to frequency using DFT and i am trying to smooth the DFT data, in ...
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29 views
Wind turbine vibration analysis approach
This is going to be a bit of a long post. My questions are:
Do the 5 signal processing steps look "correct"?
Next steps could be to perform order analysis, and extract features from time, frequency, ...
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13 views
Spectral kurtosis on non-stationary signal
I posted a question some weeks ago I still have not found an answer to. I updated the old question and am hoping someone could help.
Link:
Varying speed of shaft Spectral Kurtosis
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Is non-causal, non-LTI solution to difference equation correct?
Find a solution to the difference equation $y[n]-\frac{5}{6}y[n-1]+\frac{1}{6}y[n-2]=\frac{1}{3}x[n-1]$ that is neither casual nor LTI, where $y[0]=y[1]=1$ and $x[n]=\delta[n]$
The homogenous ...
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Interest in adapting signal processing for reverse engineering principally from a biogenomic standpoint [closed]
NB: Cross-post to this post on reverseengineering.stackexchange.com.
I am seeking any possible help for a problem I have devoted a quite protracted period of time exploring. I am total perm disabled, ...
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2answers
37 views
Impulse response of an LTI system given the input and output signals
I have been given the input and output signals of an LTI system as:
$x[n] = (\frac{1}{2})^nu[n] + 2^nu[-n-1]$
$y[n] = 6(\frac{1}{2})^nu[n] - 6(\frac{3}{4})^nu[n]$
I have found the system function $...
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26 views
Discretizing my continuous system in Matlab
I was hoping someone could help me with conducting my discretization in MATLAB.
I have a linear system with known data: sampling interval $T$, system matrix $\mathbf{A}$, input matrix $\mathbf{B}$, ...
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Do we need a transmit and a receive filter in a OFDM transceiver system? [duplicate]
can anyone specify in brief what are the filters that can be used as a transmit and receive filter in OFDM. Any material to start with will be very much appreciated. Thank you!
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64 views
Rectify signal basic question
When rectifying a signal by squaring it, is it necessary to upsample by a factor of 2?
Why is this?
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2answers
100 views
Show Equivalence Between Multiplication in Time Domain to Convolution in Frequency Domain
My goal is to compute the Fourier of the product between two discrete time signals, y1 and y2. This can be done by computing the convolution between the fourier transform of y1, f1 and the fourier ...
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1answer
42 views
Proof for the solution of homogenous difference equation
Suppose the output $y_h[n]$ of a linear, time-invariant system is described by by the following equation for input $x[n]=0$,
$$\sum_{k=0}^{N}a_k y_h[n-k] = 0$$
My book states the $y_h[n]$ is in fact ...
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30 views
Canceling interference (such as harmonics from out of band source )
I have a vague-ish question, if it makes sense:
The desired received signal (from source S1) was carried at 3 GHz passband carrier frequency, with bandwidth 20 MHz. It was interfered with by the 3rd ...
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2answers
73 views
FFT looking messy after filtering process
I have a vibration signal (25.6 kHz) which has been through the following filters:
...
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0answers
28 views
Time domain to angular domain approach
I have a rotating shaft where I need to move from the time domain to the angular domain to look for vibration faults. I have the data from a tachometer.
From another post I found these steps:
The ...
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1answer
39 views
Upsampling question- Aliasing/imaging problem
I'm trying to study vibrations in a non-stationary shaft by upsampling the original signal.
The original sample rate is at 25.6kHz, and it is being upsampled to 36kHz. In the FFT of the upsampled ...
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1answer
25 views
how can the channel fading model (Rayleigh, or Rice, or Log normal distribution) infer the way channel estimation is done?
For a dense urban environment with rich scattering and no Line of sight (LoS)
path, the Rayleigh distribution can be used to model the fading.
Rician fading is a stochastic model for radio propagation ...
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0answers
34 views
Strange FFT spectrum after resampling
I'm pretty new to signal processing and have encountered strange behaviour.
I have a vibration signal from a non-stationary gearbox component that I need to resample to do order analysis. The ...
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1answer
49 views
Why is it assumed that $x[n]$ is limited from $0$ to $N-1$ while evaluating DFT?
I am a total beginner in this topic of DFT. I get that the series must be finite for DFT calculation. But everywhere we are assuming that this series must be limited from $0$ to $N-1$. How to evaluate ...
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1answer
49 views
What is the effect of padding zeros to FFT on time domain ? (opposite of what is usually done)
As above. I know that zero padding in time increasaes frequency resolution but I'm having a hard time to understand the opposite. How would you interpret that?
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1answer
21 views
Frequency change detection in step-wise frequency chirp
I am driving a system with a step-wise frequency chirp from 50-400 hz with a frequency step of 0.01 hz. I am having difficulty identifying the points of frequency change as the data collected has an ...
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1answer
26 views
How do you find the phase of the DFT of a discrete signal?
My question is similar to this one and this one, but neither answers address my concern.
Suppose you have a signal x(n) = {-1,2,-3,2,-1} where we can assume x(0) = -3. So this is an even signal.
...
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1answer
19 views
What is the relation between PCM amplitude values and the values in a Spectrogram?
I am curious to know the relation between the 16-bit amplitude values in the PCM-encoded signal and the values inside the corresponding spectrogram. I am using Scipy reading a 44100-sample rate song:
...
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2answers
48 views
Typical shape detection algorithms
Here is my target, given a set of consecutive discrete 1-d data points within a window. I want to know whether there are good algorithms to detect certain typical shapes of the signal in the window. ...
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0answers
21 views
What steps and methods are recommended to process various signals of a IMU sensor [closed]
I'm new here because I'm making my degree final project. See more my profile for more information.
I want you to recommend me what are the tools to analyse the sampled signals and process them in ...
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24 views
How to compute the LMS DFE based equalizer FF and FB coefficients in a adaptative way?
I am still struggling to understand the filter updating process, the computation of the demodulated result and the computation of the error.
Attached you can find the simulation I've done so far, the ...
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0answers
26 views
Varying speed of shaft Spectral Kurtosis
I want to perform Spectral Kurtosis (Kurtogram) on 10-second vibration signal of 25.6 kHz sample rate, where the shaft is varying in speed.
Will a preprocessing step of resampling the signal be ...
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1answer
24 views
Serial to Parallel Converter
in many texts about modulators I have seen there is a component called "Serial to Parallel Converter". For instance, let's consider this scheme and let's focus on the second block (reference):
The ...
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1answer
43 views
What does filtering do to a signal in time domain? Does the signal gets distorted?
When considering a transceiver system, if we do a certain filtering operation on the signal, will the BER of the system be affected? My point is, since filtering in frequency domain filters a portion ...
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41 views
Calculation average signal power and Eb
I am working in a project and I would like to add noise to my received signal, but I would like to add the noise according to the value of $\sigma$, $$\sigma^2 = \frac{(1/No) \times sps \times Ps)} {...
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43 views
Can someone explain or elaborate on the channel estimation and noise variance estimation algorithms used in HF receiver?
For different type of communication, there is different type of algorithms to acquire CSI.
For instance 4G (LTE) network have SRS or DMRS to estimate the channel based on pilots.
I am designing a ...
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21 views
How to find phase of two fixed Gaussian of periodical signal (analytically)?
For a periodical signal define on $\phi \in [0, \pi * 2)$,
there was supposed to be two peaks,
may following Gaussian, but may also be Cauchy or other distribution with one peak,
plus Poisson noise.
...
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2answers
31 views
Can some one explain what is the meaning ( in real life) of anti causal (precursor) part of the channel taps?
The channel taps are classified into postcursor (causal) and the precursor (anti-causal) parts.
\begin{equation}y_{k}=\sum_{l=-L_{2}}^{l=L_{1}} h_{l} x_{k-l}+n_{k}\end{equation}
here $h_{l}$ is the $...
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2answers
57 views
In z-transform, if z means “delay”, why do we talk about the value of z?
I've been watching MIT's signals course and trying to understand $z$-transform. The course introduces $z^{-1}$ as an operator that delays the signal by $1$ time unit (which works very well with the ...
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29 views
Hydrophone signal calibration by frequencies
First of all excuse me if anything I post is completely or partially wrong (or poorly explained), I am new in signal processing and still learning a lot from this community, I will do my best to ...
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1answer
34 views
Correct signal analysis flow (Wind Turbine vibration)?
I have vibration data from WT (gearbox) sampled at 25.6 kHz. From a previous post I received a lot of good recommendation.
What I am trying to do:
Find early stage bearing faults by using an ...
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0answers
14 views
How to compute the DFE based MMSE equalizer FF and FB coefficients in a non adaptative way?
I seek your assistance,
I am reading the Proakis 5th edition and I came across a paragraph explaining the tuning of DFE filters, i.e, how to compute the FF(FeedForward) and FB (Feedback Filter) ...
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1answer
58 views
Z-Transform and DFT
I have $$H(z) = \frac{\left[b_0 + b_1 \cdot z^{-1}\right]}{\left[1 + a_1z^{-1} + a_2 \cdot z^{-2}\right]}$$.
Why is it that I can calculate the spectrum between $0$ and $0.5 \cdot f_s$ by calculating ...
2
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2answers
144 views
Linear and Circular Convolution in Fourier Domain (DFT)
Suppose we have two vectors A and B of length 100 and 80 obtained as a function of time. If we wish to perform convolution of the two vectors in the Fourier domain, we need to multiply the Fourier ...
2
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1answer
113 views
How to Reduce Phase Lag Caused by Kalman Filter
Background
I have been developing a system using a moving robot with a distance sensor against another robot. I want to control these robots by estimating relative velocity and acceleration derived ...
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1answer
37 views
How to match zero-pole diagrams to their frequency responses (Discrete Time)
I get confused when there are a lot of zeros/poles in the zero-pole diagram and I find difficulty understanding their frequency response.
I know the following:
1. Complex conjugates cause double ...
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1answer
89 views
Real-valued DTFT
Now this is a simple question, but I still ask it for clarification:
I know that an even signal $$h[n] = h[-n]$$ results in a real-valued DTFT (we have proven that in class). Now my question is the ...
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1answer
33 views
How to simplify multiple addition and convolution operations into one convolution kernel
I need to perform such a conversion to simplify my image processing problem (sharpening, in green are the knowns, in red the unknowns):
\begin{align}
y(n,m) &= \color{green}{x(n,m)} * \left[ \...
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2answers
85 views
Envelope analyis basic question
I have a vibration signal sampled at 25.6 kHz, and I want to perform Envelope Analysis on it.
"Vibration-Based Condition Monitoring of Wind Turbines" by T. Barszcz has the following figure:
I ...
1
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1answer
117 views
Evaluating the continuous Fourier transform of a constant, and matching it up with the FFT result
I am following my optics textbook (Optics, by Eugene Hecht), throughout which are given various exact analytical results for the diffraction patterns that result from light passing through differently ...
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3answers
87 views
Is $\cos(\pi \sqrt n)u[n]$ stable?
I took a z transform and got a double pole at $z=1$, but I don't know if that's correct.
I'm lost because I don't know if $\cos(\theta)$ converges or diverges or what that means for $h[n]$ being ...
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18 views
Code implementation of Channel estimation based DFE Equalizer in matlab (or octave) without the the signal processing tool box
I want to implement a DFE in matlab without the signal processing toolbox:
I have two filters ( FeedForward and FeedBack) with taps length equal to 15.
I know the update equation of the LMS ...
