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
9 views
Plane Settings of the Matched $z$-transform Method
I've come across that the matched $z$-transform maps poles of the $s$-plane design to locations in the $z$-plane. My question is, what is the $s$-plane and what does this mean? I'm aware that the ...
0
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1answer
34 views
ADC and Matched Filtering
A basic theorem in communications is the matched filter maximizes the SNR at sampling. I'm a little confused on how this relates to discrete time systems and sampling rate.
Normally if you sample at ...
0
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1answer
23 views
Time Setting of $z$ and Laplace Transforms
I'm aware that the z-transform and the Laplace Transform have an analogous relationship but I want to be doubly-sure that the z-transform only works in discrete-time and that the Laplace transform ...
0
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1answer
17 views
Differences in moving window rms due to sampling rate
I have a 10 second recorded signal band pass filtered from 100-500 Hz. The original sampling rate is 10 kS. Now I run a moving window RMS with a window length: 10 ms on the signal (10/1000 * sampling ...
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0answers
28 views
PLL carrier recovery: intermediate versus baseband
When looking at carrier recovery, a PLL is often applied to correct the frequency offset between the local oscillator and the transmitter after down conversion.
I'm wondering what happens to the PLL ...
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0answers
6 views
How to match resolution of two or more signals
I have received the following 4 time-series signals and wanted to do some data analytics using these. Although the sampling is the same for all of these signals, 2 samples per second, problem is that ...
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0answers
17 views
IFFT, negative frequencies and noncausal impulse
When using the IFFT to compute an approximation to the IDTFT, frequency range is 0 to 2$\pi$ versus $-\pi$ to $\pi$. This produces a different impulse sequence(causal I think).
How do you calculate ...
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2answers
24 views
Does a phase rotation introduce a delay?
Suppose I have 2 complex time series, $x_1$ and $x_2$.
If I measure the delay between $x_1$ and $x_2$, I get $t$.
If I make $x_2 = x_2 e^{-j 2 \pi 10}$, and measure the delay between $x_1$ and $x_2$...
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1answer
16 views
Equivalence of difference equation with system of difference equations
I have this system and tried to write down its difference equation as follows
$$ y[n] = b_0v[n] + b_1v[n-1]\\
v[n] = x[n] - a_1v[n-1] $$
I was asked to prove that the system can be ...
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2answers
27 views
Confused in difference between sequence versus signal?
I am learning basics of signals and systems with MATLAB
If i create a vector in matlab such that
x=[ 2 5 10 20], will it be considered a sequence or a signal?
As ...
2
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0answers
37 views
Multiply signal $x[k]$ with $\cos(2\pi\nu_0k)$, then given $X(\nu)$ draw resulting function in frequency domain?
Let
$$y[k]=x[k]\cdot \cos(2\pi\nu_0k) .\tag{1}$$
Then, given a signal $x[k]$ with the DTFT $X(\nu)$ according to the following figure
what will the frequency domain for $Y(\nu)$ look like for a ...
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1answer
25 views
what is the output of MFCCs?
I had calculated 13 MFCCs coefficients of a speech signal and i got output in the form numerical vectors please see below figure.
My confusion whether it is in time domain or frequency domain.
suppose ...
1
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1answer
25 views
Downsampling by block averaging
Many spectroscopic detectors used to study light absorbance as a function of time. These detectors cab sample data at 160 to 250 Hz. There is an option of choosing lower sampling rates such 80, 40, 20,...
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2answers
42 views
Contradiction while using the convolution sum for a non-LTI system
In a recent quiz, we were given the following problem:
The cascaded LTI systems $\mathcal{T}_1$ and $\mathcal{T}_2$ respectively have impulse responses $h_1[n]=\delta[n+3]$ and $h_2[n]=\delta[5−n]$....
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1answer
34 views
Matlab FFT not producing symmetric spectrum
I am plotting a FFT of a sampled RC pulse but my resulting spectrum isn't symmetric - it's offset.
...
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0answers
10 views
Punctured Turbo Code Decoding: Convergence Issue
I have been trying to create a basic BCJR decoder for a rate (1/2) punctured turbo code. The puncturing is simple, the encoder alternatively selects between the parity bits generated by the two ...
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2answers
55 views
Convolution of Two Impulse Signals
I have encountered convolution of two different impulse signals.
...
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0answers
29 views
how can I know this system is Time invarient?
y(t) = 0 (t<0);
x(t) + x(t-2) (t>=0);
y(t) = 0 (x(t) < 0);
x(t) - x(t-2) (x(t) >= 0);
y[n] = x[n] (n>=1)...
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0answers
10 views
Frequency warping while creating filter coefficients
If I have an audio signal at 16kHz with frequencies band-limited to 8kHz. I want to low-pass filter this signal such that fc=4000Hz. Meaning when I reconstruct the signal I do not want any content ...
0
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1answer
26 views
Please help me understand this paper about Discrete Wavelet Transform!
I am trying to understand this paper says.
I have found this paragraph to be vague:
(a) Preprocessing Stage. The first step in this stage was to apply the
Discrete Wavelet Transform (DWT). This ...
6
votes
3answers
537 views
Compress a signal by storing signal diff instead of actual samples - is there such a thing?
I am working with EMG signals sampled at 2kHz and 16 bits, and noticed that they "look smooth", that is, the signals are differentiable, and if I apply a "diff" function (...
0
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1answer
44 views
Time delay estimation between two complex signals(IQ)
I need to time align two complex signals. The two signals obtained were at different RF frequency before digitisation. So,I have two complex signals(IQ) and I need to do delay estimation and apply ...
1
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2answers
35 views
What exactly is captured in a Sample of the Nyquist-Theorem variety?
I'm new to DSP and was thinking of sampling in the traditional music creation way, in that you capture a sound and play it back, warp it, etc., but when I thought about the Nyquist theorem, I realized ...
0
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0answers
23 views
Chirp resolution as a function of bandwidth
My question concerns about the Chirp resolution during the crosscorrelation as a function of the sampling rate and available bandwidth. Suppose at a transmitter a chirp signal is transmitted (ranging ...
0
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1answer
35 views
DTFT frequency range
$$X(e^{j\omega}) = \sum_{n=-\infty}^\infty x[n] e^{-j\omega n} $$
The frequency term $\omega$ in DTFT is normalized as $\omega = \frac{\Omega}{f_\mathrm{s}}$
$\Omega= 2 \pi f$ is the angular ...
4
votes
2answers
159 views
Removing step-function like noise from signal, knowing when the step functions occur
So I currently have a system which is fit for very short time measurements. Whenever a measurement is long, however, there is a need to continuously update the reference, which, each time, will ...
0
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0answers
40 views
What is the error rate in compressed sensing?
Let $x \in \mathbb{R}^n$ be a $k$-sparse vector. Given $A \in \mathbb{R}^{m \times n}$, we have a measurement vector $y$ given by
$$y=Ax$$
Let $\hat{x}$ be defined as follows
$$\hat{x}:=\arg\min_{z\...
2
votes
2answers
78 views
Doppler Shifting A Chirp Signal
So I have a digital linear chirp signal:
$$ x[n] = \sqrt{\frac{2}{N}} \cdot \cos\Big( 2 \pi \frac{f_{0}}{f_{s}}n + \pi \frac{B}{N} n^{2}\Big) $$
Where $f_{0}$ is the initial frequency, $f_{s}$ is ...
0
votes
1answer
25 views
Discrete-time, second-order section, direct-form II filter
I found dfilt.df2sos in Matlab and trying to figure it out how do I do that in Python? Is there any function that works similarly with the Matlab function?
I also ...
0
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0answers
24 views
How to calculate Continuous Wavelet Transform (CWT) for specific frequency range in Python?
I am new to this topic pardon if I ask stupid questions.
My first question what is a scale and how to convert it into a frequency?
Secondly, I want to get cwt of a signal, but I want to have the ...
1
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1answer
47 views
Classifying and filtering out noise from zero crossings
Note: I know absolutely nothing about zero crossings nor signal processing in general. However, I am doing programming exercises that require them. I've searched around but I cannot understand most of ...
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0answers
33 views
Find output from a system with x(n) = u(n)
I've started learning signal processing and I'm trying to understand this exercise:
Assume an LTI system, described by the difference equation:
$$y(n) - y(n-1) - 6y(n-2) = x(n-1)$$
Q: Find ...
-1
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1answer
26 views
How to get descrete fourier tarnsfom [closed]
Could anyone explain me please how to produce descrete fourier transform of such signal? There are no anymore information besides the picture in this task.
0
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1answer
44 views
Reconstructing a signal from FFT by adding individual signal components
I'm attempting to reconstruct a signal from the DFT of the signal. I tried to do it by extracting the individual sinusoids and adding them up, but the answer I get is incorrect.
...
1
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1answer
73 views
Moving average filter for sound in MATLAB
y[n] = b0x[n] +b1x[n-1]
I have this MA filter in matlab as following
...
1
vote
1answer
39 views
What is used to initialise difference equations that require data from the output?
Given some difference equation for a filter like
$y[k] = ax[k] + bx[k-1]+ cy[k-1]$,
how would you initialize it? Since it needs an old output value (feedback) to calculate the new output value, it ...
0
votes
1answer
20 views
Double check z-transform ROC of $a^nu[n]$
For the z-transform ROC of signal $a^nu[n]$, it has been computed to be $|z|>a$. For example (as I have found on Wikipedia), the signal $(\frac{1}{2})^nu[n]$'s ROC will be $|z|>\frac{1}{2}$, as
...
0
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1answer
38 views
Plotting the Phase Response
I would appreciate it very much if someone would be able to provide some clarity on plotting phase responses.
For instance, given that the frequency response of a filter can be written as H(exp(j*&...
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0answers
20 views
Impulse response of discrete time system
I am learning about discrete systems and in this derivation something struck me as quite odd. Solving for $A_0$ in this equation seems dubious as it ignored all other values of $n$. For example, at $n=...
0
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1answer
41 views
How to find lattice coefficients of all pole IIR filter with filter coefficient $k_m$ is 1?
Given the following system function
$$ H(z) =\frac{1}{1+\frac{2}{3}z^{-1}+\frac{5}{8}z^{-2}+\frac{2}{3}z^{-3}+z^{-4}} \tag{1} $$
We have to draw lattice structure for above system function
The ...
0
votes
1answer
40 views
Finding period of a square wave with varying sampling frequency
I have a square wave (0-1.8V) with a varying sampling frequency (from a circuit simulator). It is also not a perfect square wave (the high and low signal could be very close to but not precisely zero ...
0
votes
1answer
40 views
Discrete Time Convolution Example
How did we get this final answer in example in fig attached.
I understand that delta(n) is a DT unit impulse where it is 1 at n = 0 and zero elsewhere.
I understand that u[n] is a unit-step where it ...
2
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2answers
50 views
Significance of modular arithmetic in DFT?
In what ways does modular arithmetic plays a part in DFT?
Why is it a so integral part of DFT?
2
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2answers
52 views
Periodicity of sum of discrete signals
In my lecture slides for school and from this website here
"The sum $z[n] = x[n] + y[n]$ of periodic signals $x[n]$ with fundamental period $N1$, and $y[n]$ with fundamental period $N2$ is periodic ...
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1answer
37 views
Help me understand the stages involved in filtering a signal using Discrete Fourier Transform
I have a series of discrete values measured from a sensor. I want to filter the frequencies coming from this sequence of values. Then, if I understood the process correctly this is what I do:
I ...
0
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1answer
16 views
Defining bound on input signal to test accumulator for BIBO stability
For an accumulator, defined as shown in the image below, why would I define $B_x=1$? $u[n]$ is defined at zero so my (possibly misguided intuition) is telling me that I'd choose $B_x = 0$ to not ...
3
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0answers
27 views
NLMS algorithm for a MISO structure
I am trying to implement an NLMS algorithm for a multi-input single-output(MISO) structure.
We take a reference signal x, then we made a new set of P input signals from it as follows: x_op (k) = x(k)...
0
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1answer
24 views
For discrete wavelet transforms, is redundancy needed to ensure perfect reconstruction?
So I was using pywt and I noticed that in the padding mode documentation they explain the following:
DWT performed for these extension modes is slightly ...
0
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0answers
36 views
Please explain Multiplication property in Z transform?
I am having problem visualizing contour any example will be great help.
As far as as where I need it I was trying to find Z transform of a contracted signal by first multiplication by impulse train.
0
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2answers
46 views
How to select the sampling frequency when the input signal frequency is not known
I am trying to observe the noise produced by UPS present in our lab, under no load (a normal running condition when its power is on). As I don't know its frequency range, I have randomly chosen 4 ...
