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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Total Harmonic Distortion THD for the rectifier
I have a circuit with rectifier and this cause the non-linearity and consequently harmonic. I show it on the oscilloscope and then collect the signal from the oscilloscope to the computer by using the ...
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16 views
Good links or tutorials to understand how a signal is represented in linear equations [closed]
Facing issues in understanding signal representation in this form x(n,k) and not able to get relation between n & k in simple terms.
Any links or guidance will help in understanding mathematics ...
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Difference between Cepstrum and Spectral Envelope
I have no background in Signal processing and i don't understand the difference between cepstrum and spectral envelope.
IDFT of the log magnitude of the DFT of a signal is cepstrum then what is ...
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1answer
20 views
How to draw a finite-duration sequence
On page 359 of the 2nd edition of the book "Signals & Systems", by Oppenheim and Willsky, the authors wrote the following words:
"Consider a general sequence x[n] that is of finite duration. That ...
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28 views
How can we do exact simulation for digital systems? [closed]
In digital control system, there are two basic techniques for finding the best digital controller.
First, called the discrete equivalent, we find the continuous compensation and then discretize (best ...
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1answer
30 views
convolution expression h(n,k) = h(n-k)
As a new to DSP concepts want to understand the meaning of impulse response and why we do $h(n-k)$ in convolution and $h(n+k)$ in correlation.
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1answer
38 views
Why is DTFT of $e^{jn\omega_0}$ an impulse train?
update : After asking the question, I figured out that DTFT result is an impulse train. Now my question evolved to, how it is derived in this way?
Using the DTFT formula seems not to be working, ...
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2answers
54 views
FFT Phase interpretation of input signal with non-integer number of cycles in FFT window
It is known that if we take the FFT of a signal at such a frequency which has non-integer number of cycles in the sample window we get different value of phase even if the original signal was at phase ...
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2answers
196 views
Phase difference between signals sampled at different frequencies
I want to know that if it is possible to measure the relative phase difference between a signal that has been sampled at two different locations with different sampling frequencies? Also can that ...
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1answer
34 views
Impulse response of a system in z domain
The question 3-23 in the "Discrete-Time Signal Processing - Second Edition" is:
and the solution is:
I cannot understand the solution. In the second row of the answer when I multiply (-4) with ...
2
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1answer
55 views
What did I do wrong with this simple filter build?
I tried to put everything I have learned from people here together to code my first filter from scratch. Unfortunately, it didn't go well and I'm not getting the expected output. The math/code became ...
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1answer
17 views
DFT practice question
This is probably basic but as I am new to the field it confuses me a bit.
While looking at some solutions provided to a problem in the final step following happens:
$$ \frac{1}{10}\sum_{l=-\infty}^{\...
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12 views
convert analog voltage into discrete time signal. show in time domain graph [closed]
Convert the analog voltage E(t) = 5 sin(2*pi*t) mV into a discrete time signal and
show your answer in time domain graph. Specifically, use sample time increments
i)1/8 second
ii)0.75 second
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22 views
IID noise assumption at Matched Filter sample time
I read that at the correct sample times of a matched filter output the noise is independent assuming a Nyquist pulse.
Can someone provide a proof of this or explain it more? Assuming your matched ...
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1answer
33 views
Impulse and step response
While trying to determine the unit step and impulse response for a discrete LTI system I had several problems:
$(Hx)[n]=(Hx)[n-1]+\frac{1}{N}(x[n]-x[n-N]) \& x[n]=(Hx)[n]=0 \forall n\lt0$
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14 views
Calculating average power of a discrete random signal with complex values
I have a Rayleigh channel that transmits discrete values according to the following:
$$y(n) = h(n) * s_n + \omega_n$$
Where $y$ is the received message, $s_n$ is the symbol sent (constellation 2-PSM), ...
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2answers
25 views
Proving for windowing function
Prove that $1+2\cos(\omega)$ is the same as $\frac{\sin(\frac{3\omega}{2})}{\sin(\frac{\omega}{2})}$
Knowing that
$$p[n]=\sum_{k=-1}^1 {\delta[n-k]}=\delta[n-1]+\delta[n]+\delta[n+1]$$
Doing the FT ...
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What is the difference between SFO (sampling frequency offset) and SCO (Sampling clock offset)?
What is the difference between SFO (sampling frequency offset) and SCO (Sampling clock offset)?
I think they are essentially the same phenomenon?
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1answer
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Discrete signal - fourier transform coefficient period [closed]
if I have an example signal in the picture, how can i decide its period?
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1answer
26 views
Confused about filter's cutoff frequency in rational sampling rate converter
A interpolator which increase sampling rate by L times is followed by an anti-imaging filter, the filter is said to have a cutoff frequency of Fs/2L. Is Fs here is the frequency before or after ...
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19 views
Applying Wavelet on energy disaggregation as denoising technique to remove uncertainties
I would like to apply Wavelet in MATLAB as a denoising technique on Non-Intrusive load Monitoring data. The data was captured by sensors on each appliance and one sensor on the smart meter (Normally ...
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30 views
Deep Learning based NDA Channel Estimation
I was wondering if it is possible to use Deep Learning to estimate the Channel Impulse Response for NDA synchronization?
I understand Deep Learning is not normally used for regression problems but I ...
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1answer
25 views
How to Emulate Sample Frequency Offset for OFDM in Matlab?
I am studying the effect of sampling frequency offset on OFDM, and in order to emulate SFO, I have to slightly change the sampling rate of the signal. In order to have a +5ppm offset, I have to change ...
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1answer
40 views
FSK carrier frequency estimation
In the MPSK Modulations, Cyclic Spectrum Density method can give a peaks, for example for the QPSK:
But in the FSK signal, this peaks do'nt appear. How to solve it?
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1answer
34 views
What is the difference between (Sample Timing Offset), (Carrier Frequency offset), and (Sampling Frequency Offset)?
Briefly, can anyone explain to me what is the difference between (Sample Timing Offset), (Carrier Frequency offset), and (Sampling Frequency Offset)?
and is Sampling Frequency Offset (SFO) like STO ...
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1answer
34 views
Simulation of IQ imbalance using MATLAB
I already have the value of Image Rejection Ratio (IRR) in dB for IQ imbalanced modulator and I want to simulate this effect using MatLab. How can I obtain $\alpha$ and $\theta$ to calculate the ...
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1answer
32 views
How to convert from Laplace Domain to Time Domain?
I want to convert the following equation from Laplace domain to continuous time domain:
$F(s) = \frac{-2 m k v R}{2 m R s^{2} + m k s + 2 k R}$
m, k, v, R are all constants.
If I can factor or put ...
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24 views
Are discrete time functions expected to be this inaccurate?
I am attempting to test some discrete time functions against their continuous counterparts and I am surprised by how inaccurate the discrete versions are coming out.
I am modeling the displacement, ...
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9 views
(Frequency Offset): Relationship between Normalized Carrier Frequency Offset (normalized CFO) & ppm in OFDM system
How can I change a normalized carrier frequency offset (CFO) to ppm? And If the DAC sampling rate is 30GS/s, and the clock frequency is 15GHz, then should I use 30G or 15G when I calculate ppm? ...
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2answers
24 views
How do you get FFT for negative $k$ values?
I am reading a book (am a programmer so I suck at math) and it states that for a number of $k$-values that are symmetric around 0 (for example $k = -3, -2, -1, 0, 1, 2, 3$), we need to calculate
$$\...
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1answer
23 views
inverse discrete FFT in python, multiple times?
I was wondering what really happens when taking the inverse discrete FFT on some set of numbers, for 3 times? Because looking at it, it looks like we're getting an output that is identically with the ...
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1answer
42 views
One more inverse z transform … a bit more complicated
Thank you for all the help teaching me. I am looking at one more inverse z transform and not understanding what to do with it.
$F(t) = m \cdot a(t)$ (i.e. Force = mass $\times$ acceleration)
$F(s) = ...
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1answer
13 views
How to do this inverse Z-transform? Is this correct?
It was explained to me here that I need to do an inverse z-transform on a z-based equation in order to get something I can use. That example was quite simple. But I'm not sure how to do the same ...
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2answers
132 views
Justification of bilinear transform
I would like to understand the "justification" for the bilinear transform. The basic idea as I understand it is that by integration rule of Laplace transform we have for continuous $y(t)$:
$$\mathcal{...
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2answers
69 views
What does z^(-1) represent here?
I understand that when you have a Laplace function, you can do a bilinear or forward/backward Euler substitution for $s$ to phrase it in terms of $z^{-1}$. In a typical filter, $z^{-1}$ represents the ...
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24 views
How modulate and shift in frequency?
I have a 16-QAM constellation, then I divide it into imaginary part and real part. I convolve both by Srrc pulse and multiply by cos(2*pifct) and -sen(2*pifct). Let's say fc equal to 40 MHz
Now, we ...
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2answers
37 views
Even and odd signals
We've studied in signal and systems about odd and even signals. But what is the actual implementation or application of this property?
like for energy and power signals we know If you're using a ...
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0answers
31 views
How to generate Digital Sine Wave? [closed]
I am trying to generate a sine wave digitally. I am using LMS7200m RF chip from Lime microsystems. I want to generate a sine wave of 100KHz. The DAC on the chip has a sampling rate of 640 MHz with ...
1
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1answer
29 views
Noise amplification with inverse filtering
I'm trying to gain a better (mathematical) understanding of why inverse filtering is almost never the solution for correcting an image. From what I understand, we start with a discrete signal $s[n]$ ...
3
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1answer
90 views
LTI, causal, discrete time system output
Consider a discrete time LTI causal system $S: y = S(u)$, with its impulse response $h:{Z} \rightarrow R:h(n)=3^{n+1}{H(n)}$ with $H$ the Heaviside function. We know the values of input:
$$u(0) = 2$$...
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1answer
27 views
SNR estimation prior to demodulation?
What are the standard ways to measure SNR, particularly before demodulation/synchronization?
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1answer
47 views
When is a discrete time transfer function unrealizable?
I don't understand why the following makes sense:
Given a second-order mass damper system in continuous time:
$H(s) = \frac{1}{ms^{2}+cs}$
Its inverse $H^{-1}(s)$ is unrealizable as a transfer ...
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0answers
34 views
Block CMA algorithm
The Constant Modulus Algorithm is a common equalization method which adapts at every sample in an attempt to give a filter which produces a fixed power output. Divergence/convergence of the CMA ...
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1answer
25 views
Autocorrelation Computation with MATLAB
I have done the computation of the autocorrelation of a sequence (vector), here called "frame", and I have plotted it. Here the code:
The resulting graph is:
I do not understand the position of the ...
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2answers
73 views
Pulse Doppler Radar: time delay in down conversion
My understanding of Pulse Doppler Radar is the system measures Time Of Flight for the pulse.
My confusion is that during the down conversion process prior to ADC the lowpass filter causes some time ...
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1answer
54 views
NDA timing estimation for mutli-level QAM(RC pulse)
What non-data0aided techniques are used to estimate the timing for multi-level QAM? For single level QAM(so 4 QAM) you can use variance minimization or power maximization but I'm not sure these ...
2
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0answers
65 views
Lagrange Vs Sinc interpolation
I was wondering what is the practical difference between Lagrange Interpolation using Farrow Structure and Sinc Interpolation? Both require pre-computation of time offset coefficients using a lookup ...
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1answer
21 views
How to get RMS to Frequency chart for discrete samples of acceleration?
I’m reading a book on Motorcycle dynamics and want to compare the vibration profile of my motorbike against this chart:
I am not sure how to get the RMS of acceleration at different frequencies.
I ...
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4answers
82 views
Phase difference measurement of a signal sampled with two different sampling frequencies
I am working on phase interferometry for locating a transmitter. The direction of arrival of an incident wave can be estimated from the phase difference caused by the antenna separation as shown
...
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2answers
122 views
downsample signal to a specific number of samples in Python
The Python Scipy library provides several functions to downsample signals, but they all have limitations:
The resample function is based on Fourier method, which means it assumes periodic signals.
...
