Questions tagged [sampling]

In signal processing, sampling is the reduction of a continuous-domain signal to a discrete-domain signal.

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Interpolating function for the samples

Let $x(t)$ be band-limited with $B = \omega_m$. Sampling gives us $$x(nT_s) = \begin{cases} 1, & n = 0 \\ 0, & n \not = 0 \end{cases}$$ And $\omega_s = 2\omega_m = \frac{2\pi}{T_s}$. Find ...
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Reconstruct $x(t)$ from $y(t)$ and $z(t)$

Let $x(t)$ be band-limited signal with $X(j\omega) = 0$ for $|\omega|\gt \omega_M$. We use $$s(t) = \sum_{k =-\infty}^{+\infty}(-1)^k\delta(t - \frac{kT}{2})$$ for sampling. So we have $z(t) = x(t)s(t)...
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45 views

Fourier transform of the sampled signal

I want to calculate Fourier transform of the sampled signal in two ways. Let $$s(t) = \sum_{k = -\infty}^{\infty}\delta(t - kT)$$And $z(t) = x(t)s(t)$. So we have $$z(t) = \sum_{k = -\infty}^{\infty}x(...
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How to convert ofdm symbol to signal?

Hello may I know how to convert ofdm symbol generated from ifft block to an OFDM signal for the purpose of transmitting it?
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Meaning of sampling frequency?

Say there is a communication system, which can manage sampling frequency up to 4 MHz (given by software). Can the system be able to process signals with maximum frequency more than 2 MHz? Because ...
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going from output of D/C to input of D/C

$$y_c[n] \longrightarrow \boxed{D/C} \longrightarrow y(t)$$ If the following equation describes the IDEAL D/C converter: $$y_c(t) = \sum \limits_{n=-\infty}^{\infty} y_d[n]~ \text{sinc}\Big(\pi (t - ...
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Sample and Hold Circuit at Digital to Analog Converters

Does DACs contain sample-and-hold circuits? I am a bit confused thanks
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Aperture Jitter in Digital to Analog Converters

I have noticed in the literature that there is an internally induced timing jitter inside Analog to digital converters called (aperture jitter). It is caused by the sample-and-hold circuit of the ADC. ...
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Ideal low pass filter output at given sampling frequency

Consider the signal $\cos(30t)$ sampled at $w_s=40 rad/s$ using a unit impulse train. The sampled signal is filtered with an ideal low pass filter with unity gain and cutoff frequency $w_c = 40rad/s$. ...
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How should I sample the signal $f(t) = \sin(24t)^3\chi_{[0,0.52]}$ on the interval $[0,1.25]$?

I am from an applied math/PDE background and I don't usually deal with proper sampling and signal processing. I just take roughly what seems to be a good number of samples. But I would like to be ...
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34 views

Oversampling a signal

I’ve built a circuit with an analogue sensor (70 Hz bandwidth) connected to a 24 bit ADC, which is oversampling the signal at 10 kHz. Nyquist sampling theorem implies I should sample by at least 140 ...
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Oversample or undersample correlated noise?

I wish to measure nontrivial (non-Gaussian) broadband current noise for its distribution and power spectral density. The noise is amplified (with transimpedance amplifier) with some characteristic ...
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44 views

DFT without knowing the exact value of sampling rate?

I have a sequence of (real) numbers that represent the magnitude of a certain natural event. I know that the samples are equispaced in time, but not the exact value of the spacings. So does that mean ...
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29 views

Number of samples in a discrete signals after sampling a continuous periodic signal should be integer?

If a continuous periodic signal is sampled with time interval Ts , and T being time period of continuous signal -- For the resultant discrete signal to be periodic following must be true-- the ratio ...
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Upsampling implementation

I have problem with upsampling implementation in the following way: My code: ...
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1answer
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How are these 2 frequencies aliases of each other?

I'm trying to understand this solved example from a book, given an analog signal $x(t) = 3\cos(100\pi t) $. This signal has a frequency of $50hz$. If sampled at $F_S=75Hz$ ,I obtain the discrete time ...
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176 views

Sampling: question regarding sampling period

what exactly happens when I increase the sampling period ? Providing some Matlab plots so that I can be more clear. Using the signal $x(t) = \sin(10\pi t)$ and periods $T_s=0.02 ,\; 0.05 ,\; 0.1$ ...
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37 views

Multichannel sampling with aliasing

if i have 2 sensors, sensor1 and sensor2, that sample a signal on complementary points so that sensor2 samples always between sensor1s sampling points. can I achieve the doubled sampling rate with the ...
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25 views

IDFT - influence of sample numbers

I'm quite a newbie in dsp domain, and there's something I can't understand clearly. I'm doing a IFDT of a spectrum regularly spaced with complex values : the spectrum is a complex conjugate symetric ...
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49 views

Determine impulse resonse of First Order Hold (FOH)

Question, how can I determine the impulse response function of a first order hold? On Wikipedia it is simply stated as: $$ h_{\mathrm{FOH}}(t)\,= \frac{1}{h} \mathrm{tri} \left(\frac{t}{h} \right) =...
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31 views

What is the effect of sampling time, sampling frequency and SNR on latency? [closed]

I believe that if we have two or more external sound cards, hence clock would vary for each device. How will this affect the latency? Will it increase or decrease? How will the factors like sampling ...
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1answer
42 views

Cross Domain Equivalent to Nyquist Sampling Theorem?

In attempting to answer this question by @Oliver here: What characterizies 'causality' for a finite FFT? I have considered the minimum requirement to avoid time domain aliasing in the Discrete ...
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integral with vectoric varying coeficient

i have a basic function exp(-x.^2).*log(x).^2 which i integrate in a certain interval. i want to multiply my basic function with a vectoric coefficient called coef_vec that varies with the interval. ...
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30 views

Reconstruction of Contiuous - Time Signals

In terms of analog signals, we can represent digital signal as : $$ x[n] \triangleq x_{a}(nT) = \int_{-\infty}^{\infty}X_{a}(f) \, e^{j2\pi f nT} \ \mathrm{d}f $$ While if we focused on the integral ...
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32 views

Continuous frequency grid to discrete grid

I am designing a controller for a system using several methods, one of which is a discrete method. In the continuous time I am looking at a logarithmically spaced frequency grid in the range $$\omega \...
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How do you change an instance of dsp.DigitalDownConverter object in MATLAB to work with filters other than the ones it is originally defined with?

If you look at this website: https://www.mathworks.com/help/dsp/ref/dsp.digitaldownconverter-system-object.html you will see an example (with code) that attempts to up convert and down convert a ...
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25 views

Partial column approximation error

Can someone help me understanf how to plot the next partial column in MATLAB: while N=2001 |M|<700 ak =
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51 views

ZOH DAC amplitude formula testing

We have an expression shown in red bellow for non ideal DAC ZOH,which links the sampling frequency to the amplitude loss of the input signal. I took $f_b=1kHz$ and $f_{noise}=4kHz$ $f_{in}=f_b+f_{...
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ZOH non ideal sampling loss formula

Hello i am trying to calculate the amplitude loss of non ideal sampling. My signals amplitude is 10 at 70 frequency. When we sample it at Fs=400 we have al 0.511 loss as shown in plot bellow. How can ...
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87 views

CTFT to DTFT why can't you always just substitute $\Omega = \omega/T_S$

This is something I've always wondered about in DSP class, but just accept as a fact because I never really fully understand why this is the case: Given CTFT: $$X_s(j\Omega) = 6000 \pi \sum \limits_{...
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33 views

Difference between frame rate and sampling rate?

Below are the two different methods of generating time to create an audio sine wave. While framerate is being used as steps in one method, the inverse of sampling rate is being used as steps in the ...
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Contradictory results from power spectral densities and autocorrelation in shot noise

I have a white noise generator circuit which involves a Zener diode meant to undergo breakdown across a resistor $R1$, and am trying to compare power spectral densities and autocorrelation of the ...
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26 views

Time stretching allowing for pitch change

I have implemented the WSOLA time stretching algorithm for audio data, but there are still many artifacts from the stretching. I don't actually care about maintaining pitch and am totally ok with ...
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1answer
32 views

Reconstruction using sinc

The signal that I produce above. What is the reason for it to slide to the right? In oversampling at Nyquist rate can I make like below picture ? do you think the signal i produced at nyquist rate is ...
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94 views

Sampling and Reconstruction of digital signal in Matlab

I'm trying to write a program in Matlab that samples (using Nyquist theorem) and recovers signal. However, I cannot write sampling part for sum of 2 signal. ...
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Any DVB-S2 sample streams publicly available on-line?

I'm working on a DVB-S2 receiver and I'd like to be able to test a part of the DSP chain with real-world signals, but getting good sample streams from a digitizer is not terribly easy. Can anyone ...
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41 views

Downsampling issues

I have this data that need to be downsampled so that it can be fed into a classifier. The issue is that I need to downsample from 1000Hz into 20Hz. If you see the graph below, the blue line is the ...
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38 views

Remove aliasing caused by scanning a wave file at arbitrary playback rates

I am writing a sound generator that needs to scan through audio samples at an arbitrary rate. When the sample is played at it's original rate, it sounds fine. But when I change the playback speed, it ...
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1answer
30 views

function for sampling sine function

I wanted to write a function for sampling sine function with sampling frequency sf,frequency f and length l, so I wrote the function adopting from the sampling formula, what change should I apply to ...
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GPS Acquisition Graphs [closed]

I am trying to generate GPS Acquisition signals using frequency code phase search acquisition. I generated C/A gold codes and digitised at 16.368e6 MHz(sampling frequency) I generated carrier signals ...
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2answers
59 views

Up-sampling using ZOH

The basic idea of up-sampling is to add $M-1$ zeros after each sample. I need to make upsampling(factor of 3) of the function $rcosdesign(\beta, M, T)$ using the ZOH filter in Matlab. $\beta=0.25$, $M=...
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39 views

Whats the difference between spatial and temporal resolution?

Iam trying to understand how super-resolution works. But i think i have not understood correctly the difference between the optical resolution (spatial resolution?) and the resolution i know from a ...
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53 views

Is it better to use sampling rates which are a power of 2? 32-64-128-256-512Hz? instead of using for example 30- 60-100-250-500Hz?

I am recently working with a sensor that I its sampling frequency can only be configured to either 32hz- 64hz- 128hz-256hz... and I was wondering whether using such sampling frequencies have any ...
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220 views

How can I generate a sine and cosine function using an exponential function?

I have been trying to generate sine and cosine sampled graphs by a given sampling frequency. ...
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1answer
64 views

creating this famous basic nyquist theory photo

Hello i ha built this code which create a only one replica of the data, how can i create the whole photo shown bellow of many cycles as shown bellow? i read in the internet that zero padding could ...
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71 views

Types of interpolation used for reconstruction in DSP?

What are the different types of interpolation used in DSP for reconstruction of analog signal from discrete/digital signal I am able to somehow learn two types of interpolation 1st is "zero order ...
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74 views

Upsampling with time offsets

Suppose I have done 4x oversampling for a continuous time signal, but the successive sampling times have a linearly increasing offset. Specifically, the samples with indices {4k; k=0, 1, 2,...} are ...
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103 views

DFT for signals of different length and sampling rate

I would like to compare oscillations of biological object. I have multiple datasets which are taken with different sampling rate and have different length. My current workflow: Take derivative, ...
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4answers
58 views

Why is In-phase Quadrature sampling not used to record and store digital audio?

I/Q is a standard method to sample radio frequency and its use is even seen in some non radio signals like sonar. But it seems that it is not used to sample acoustic frequencies. What property of ...
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91 views

Fourier Transform of sampled reflectance measurements

Goal: Calculate the complex index of refraction ($\hat n = n +jk)$ from reflectance measurements. Data: Reflectance measurements for various materials were taken with a FTIR (Nicolet™ iS50 FTIR, ...

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