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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1answer
50 views

Measure 3-D length using smart-phone's accelerometer

I'm wondering if we can measure 3-D length only by our smart-phone's accelerometer. And we all know these low cost IMUs are not accurate. You can model accelerometer's error this way: $$ a = f*a' + g ...
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1answer
87 views

Measuring group delay through a linear phase filter

I'm having a difficult time wrapping my head around a phase/ group delay problem and it corresponding to where you start sampling so I built up a system to test some of these issues. The system passes ...
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1answer
190 views

Estimate smartphone accelerometer bias

I was planning to develop Android / iOS applications that enable users to measure 3D length using their smartphones. According to this question, you need to know at least the time-varying bias that ...
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0answers
26 views

Discrete-time convolution response on matlab using for loop

An LTI system's Unit impulse response is defined as: > n = 1:100; h = 0.08*(0.9).^n; if we give input signal as: ...
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2answers
37 views

How can I shape my time channel response, in order to have Gaussian shaped Doppler Spread?

I know how to generate a Rayleigh fading channel but I have no clue how I can shape the Doppler spectrum to be Gaussian. Any help will be really appreciated. ps: I am coding on matlab
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1answer
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Can someone explain me how to generatee a doppler spectrum? [duplicate]

I have a signal generated in matlab, with Rayleigh Fading, how can I add a given type of Doppler spectrum ( Gaussian for instance) to that signal ? Any help will be really appreciated
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2answers
40 views

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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1answer
63 views

Ways to differentiate three respiratory signals

I have three 1-min respiratory signals I derived from ECG signals. I am wondering if you guys have any suggestion on differentiating those three? The red line represents the experimental signals and ...
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1answer
47 views

“plot” command for continous time signal in matlab?uses interpolation?

We know digital computer cannot deal with continuous time signals directly. But then how MATLAB "plot" command works? Does that uses interpolation technique to show an apparently continous time ...
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1answer
53 views

Is fft2 in MATLAB unitary? Some differences happen

I meet a problem when implementing fft2 in MATLAB. The question is I try to simulate the realistic measurements $Y = |FCXF^H|^2$ - the intensity of Fourier domain of object $X$, where $F$ denotes ...
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Determine the haar wavelet function is linear or nonlinear

I'm trying to looking for analytics justification of linearity or non linearity of the wavelet transform with the real Haar mother wavelet function. I have googling already. But I can't find and ...
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How to calculate the coefficients of Auto regression model of multiple data?

I have ACF of a time series data, I want to interpolate the ACF using AR model for which I need to calculate the coefficient of the AR model The problem is I have (6000x6000) matrix of ACF and I cant ...
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1answer
56 views

How to describe correlated noise after the signal is oversampled?

The Gaussian noise in discrete signal models is usually assumed to be independent and identically distributed variables (i.i.d.). Does this mean that the signal must be sampled with the sampling rate ...
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2answers
391 views

Detection of Troughs and Notches in a PPG Signal

I'm working a project which tries to determine Blood Pressure from PPG signals.I'm trying to extract the features as shown below... I'm having problem in finding the troughs and dicrotic notch for ...
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1answer
56 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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1answer
120 views

Use samples of Fourier transform as DFT?

Consider the LTI system given by: $H(z) = 1 - \frac{1}{2}z^{-1}+\frac{3}{4}z^{-2}$ Let $x[n] = (\frac{1}{2})^nu[n]$ be the input to the system. We want to find the output for $n = 0,1,...,N_a$, using ...
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3answers
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Why integrate over $2\pi$ in inverse DTFT?

In DTFT of a signal, the spectrum of a sequence is periodic with period $2\pi$ and all the information needed for derivation of the original signal from its spectrum is contained in $\pi <\omega &...
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2answers
76 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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1answer
64 views

Reconstruction of sampled band-pass signal

I am pretty new to signal processing. I am currently trying to reconstruct a sampled band-pass signal created with the filtfilt and ...
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1answer
58 views

DFT of an audio signal stored as a multi-dimensional array

I'm using the Python scipy library to get the data of a particular .wav file into array format. Now, I'd like to find the Discrete Fourier Transform of that signal. The formula for the DFT is, $X_k = ...
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0answers
64 views

How can I extract the 2 polyphase components of a signal after sampling at the half of sampling rate

Suppose I have a continuous signal $x(t)$, which was sampled using sampling function $s(t)$ whose sampling rate is $T_s$.How can I sample the continuous signal by Ts/2 instead of Ts in order to get ...
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0answers
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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2answers
39 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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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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2answers
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what is the difference between the convolution and differentiation over image in image processing?

In image processing the differentiation and convolution are the terms that are used interchangeably . what is the difference between applying convolution and differentiation over the image ?? How we ...
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3answers
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Type of filter, given difference equation?

Given a difference equation, how do we tell if it is an IIR filter or FIR filter? For example, y(n) = x(n-3)+y(n-1) . Is it FIR or IIR? Can you please give me a way to figure this out? Thanks! :)
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1answer
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What does fir1 in matlab does?

May i know what does this function do in matlab? num = fir1(80, [5Hz, 50Hz]); I know that 5 Hz is the low cut-off freq and 50 Hz is the high cut-off freq. I'm ...
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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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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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0answers
21 views

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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1answer
331 views

Zero State and Zero Input Responses from Steady State Response

Let a linear, time-invariant, causal discrete linear system be described by the following difference equation: $$y[n] = 0.9y[n-1] + 0.1x[n]$$ Assuming that $y[-1]=2$ and $x[n]=20\cos(\Omega n)u[n]$, ...
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2answers
3k views

Performance of MATLAB's `conv2()` vs. `imfilter()`

A lot of people use imfilter to achieve a 2-D convolution between an image and a filter, but the majority of people use conv2 ...
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1answer
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Corner detection using Chris Harris & Mike Stephens [duplicate]

I am not able to understand the formula, What is $W$ (window) and intensity in the formula mean, I found this formula in opencv doc http://docs.opencv.org/trunk/doc/py_tutorials/py_feature2d/...
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0answers
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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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2answers
5k views

How do you interpolate between points in an image (2D), e.g. using splines?

I can understand just fine how to use 1-dimensional interpolation on data points where one coordinate is a function of the other: y = f(x). However, when we have an ...
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4answers
2k views

How do I compare chords played on a guitar with a known sample?

I want to create a project that will recognized the chords that i played in guitar. I recorded a raw sound to be compare to the one that the user will input. Example I have a recorded sound chordA ...
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1answer
545 views

Detecting a frequency pattern in the frequency domain

I am looking to detect a combination of frequencies in the frequency domain. For example, here is my spectrum: And I'm trying to detect the pilot tone. I have the FFT of the pilot tone: which zoomed ...
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2answers
8k views

How to use low pass filter in Matlab for discrete data? [closed]

As see in the picture, there are high frequency noise in the signal. How to design a low-pass filter to eliminate the noise? How to apply this filter in Matlab?
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4answers
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noise of zero mean and variance?

It might be a very silly question, however I'm facing problem with it. Now, the Gaussian noise is a signal with zero mean and variance. I understand what the mean and the variance mean however, I'm ...
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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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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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0answers
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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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1answer
1k views

How can I find the actual frequency given a normalized frequency?

Suppose that we have some sample: ...
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2answers
535 views

Power of summation of two signals

Let $|A|$ denote the power of the analog signal $A$. Is that true to assume $|A+B|=|A|+|B|$, for two arbitrary signals $|A|$ and $|B|$? That is the power of the summation of two signals is -at least ...
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2answers
833 views

Ways to compute the n-the derivative of a discrete signal

This is a pretty general question about how to compute derivatives of a digital signal $x[n]$. I would like to know what are the different approaches (from naive to complex) and how are they compared ...
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2answers
238 views

Can I construct a linear system so that it results in a moving average?

I've just learned about linear systems and impulse response functions. I know that in a linear system consisting of $h_1[k]$ and $h_2[k]$, the impulse response of the system is $h_1[k] \ast h_2[k]$. ...
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1answer
241 views

Getting different results when running my program at different times [closed]

I am working on Speckle Noise reduction in Ultrasound Images using MATLAB R2013. I have designed 10 basic filters and trying out hybrid combination using these filters. When I run my program I get ...
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5answers
4k views

How to separate a low amplitude signal of same frequency but different phase

I have a signal consisting of two sine waves of same frequency but have different phase (and also a lot of HF noise). Their amplitudes differ by about $120\textrm{ dB}$. How to I go about separating ...
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0answers
22 views

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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2answers
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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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