Questions tagged [sampling]

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

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Multiband undersampling

In Practical Signal Processing (Marc Owen), an exercise explore the topic of undersampling: [...] Suppose you know that an audio signal is a sine wave with a frequency that might be in one of two ...
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Model-based Kalman filtering a noisy signal

In a healthcare application, I need to calculate urine flow by differentiating the mass of urine emitted by a person over time. The measuring instrument consists of a load-cell under a fluid container,...
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Understanding Upsampling filter in Laplacian Pyramid

For the construction of a laplacian pyramid, images are downscaled and then upscaled again. My question is what is a wise decision of the kernel mask for the upscaling task ? In more detail, lets say ...
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Sampled AC Voltage measurement

I want to implement a AC Voltage measurement function for a DMM. That DMM can sample up to 1,000,000 Samples/s. With the sampling function I wanted to sample an input sigal (e.g. sine signal) and ...
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PSD of Quantization noise [closed]

Psd of Quantization noise Psd of Granular noise Are above PSDs correct
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Bandwidth of Time Division Multiplexing

Why is it said that bandwidth of output of a TDM transmitter is half of Sum of individual sampling frequencies.Is their a mathematical proof. I know that sampling frequency should be greater then ...
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Should I sample at twice the bandwidth or twice the highest frequency?

I am confused about what rate I should sample at. I've heard 2 different ways: 1) Sample at twice the highest frequency 2) Sample at twice the bandwidth If I have a signal composed of just cosine, ...
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Absolute convergence of periodic sinc interpolation

An $N$-periodic complex discrete-time sequence $[x_0, \dots, x_{N-1}]$ can be resampled to an $M$-periodic sequence $[y_0, \dots, y_{M-1}]$ with $M>N$, using sinc interpolation: $$\begin{align}y_m ...
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31 views

Why does downsampling stretch a signals frequency response and upsampling shrink and create images of a signals frequency response?

I am learning some basic DSP and I have a pretty good intuition as to why sampling creates spectral images of the frequency response at intervals of the sampling frequency (convolution with pulse ...
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Phase measurement with FFT for DMM Keithley 7510

I am currenly working on a measurement driver for the DMM Keithley 7510. I implemented a harmonics measurement using FFT (from MathNet library). First I simply sample my input voltage signal and ...
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65 views

Real signal from I,Q, sample rate and center frequency

I am given a recording of an ionosonde sounding. The signal $S$ is represented as a series of I/Q pairs at a sample rate $F_{sr} = 10\,\text{MHz}$. I am told that the center frequency of the ...
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What happens when the frequencies of the signal does not lie within the reconstruction filter passband?

Assume we have an analog signal that has frequency components between 40Hz and 50Hz and 0 otherwise. If we sampled this signal with 100Hz sampling frequency then passed to DAC with the same sampling ...
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Discrete Frequency Equation and Relation

I think I am looking at conflicting equations from a few sources, or maybe I just dont understand it. $ \Omega $ is Discrete frequency $ N $ is Discrete Period in number of samples $ \omega $ is ...
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Bandpass filter with very high sampling rate

Consider a bandpass filter with Low Cut 17Hz, High Cut 22 Hz, Fs = 45000 Hz and Order = 6. When I pass a mixture of multiple sinusoidal waves through this filter (with a sine wave of frequency 20 Hz), ...
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Calculate aliasing of $x_a(t) = \cos{(2\pi300t)} + \cos(2\pi600t)$ when sampled with $F_s = 1000$

I'm asked to sample the signal $$x_a(t) = \cos{(2\pi300t)} + \cos(2\pi600t)$$ with sampling frequency $F_s = 1000$ and plot the magnitude spectrum for the resulting sampled signal. My thinking is ...
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DFT: a function of $n$?

I‘m a high school student and I haven’t studied physics or anything. Why does the DFT depend on an integer, say $k$ or $n$ (it’s usually expressed like $F(n)=...$ or $F(k)$ or $F_k$, etc.) if it is ...
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In the Sampling Theorem, why are the image frequencies at n*fc not a problem?

In this example I have been working through, we first look at the situation when fs > 2fc and then the situation when it isn't: In the example, the frequency responses of a sampled sinusoid at fc = 5 ...
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Frequency selective channel modeling using rayleighchan object in matlab

I intend to model a frequency selective channel using matlab "comm.RayleighChannel" object. Consider the following command, which sets the parameters of Rayleigh channel : ...
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What does a fractional frequency (for discrete-time signals) mean/how to interpret it? [closed]

This question has bugged me for a while as it's not addressed in any books I've read. I was wondering how folks from this community interpreted it. Below are my personal notes on the matter (please ...
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Why doesn't sampling a periodic continuous-time signal yield a periodic discrete-time signal?

I have been studying signals and systems lately and I have came across the following claim: The uniform sampling of a periodic continuous-time signal may not be periodic! Can someone please ...
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Conversion from continuous to sampled signal?

I am bit confused regarding sampling as i read different types of statements in different texts Forexample i have a continous time signal $x=sin(t)$ defined for $t=0:10$ and i want to sample it with ...
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35 views

Not sure how to perform ZOH upsampling

Sorry if the question looks pretty naive. My goal is to up-sample a given signal x[n] by a factor of M using the zero order hold interpolation function. The basic idea of up-sampling is to add M-1 ...
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How can an SDR recover a high-frequency signal?

How can software-defined radios operate at high frequency? The Nyquist rate dictates that you need to sample at twice the frequency to fully recover the signal. If my signal of interest is modulated ...
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When Two Sampled Sinusoidal Are Orthogonal?

If two analog sinusoidal are orthogonal with duration T, their minimum frequency difference should be 1/2T in case of no phase offset between them. And if there is phase offset, the difference is 1/...
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Usefulness of Matched $z$ transform Method

I'm aware that the matched $z$ transform method maps between the continuous $s$ plane and the discrete/digital $z$ plane but my question is - when would this be necessary? Why would we need to convert ...
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barker sequence in signal processing

In our class test we were given a signal with barker sequence and a 10101010... sequence ahead of that and were asked it's importance. So what is the significance of that 10101... sequence?
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Periodic non-uniform sampling - effective bandwidth to select correct anti-aliasing filter

What is the effective bandwidth of sampling at a rate $f_s$ for a burst of $N$ samples, where the bursts are triggered at rate $f_B$? For example, say $f_s \approx$ 10 kHz, $N \approx$ 1000 and $f_B \...
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Fourier transform of dirac comb with function: The scaling factor

Multiplication in the time domain corresponds to convolution in the frequency domain: $$ f(t) \cdot x(t) \iff F(j \omega) * X( j \omega) \tag*{No scaling factor} $$ I know the fourier transform of ...
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Question about sampling

Is it possible to represent an aperiodic signal using an array of N samples? I am confused about this because you obviously have to window a function in the time domain to sample it. Now what ...
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Sampling Theorem for images

A medical Image has a size of 8x8 inches. The sampling resolution is 5 cycles/mm. How many pixels are required? Will an image of size 256x256 be enough? I know sampling in 1D signal but cannot get ...
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Practical Signal Processing by Mark Owen Exercise 2.1. and 2.2

The following exercises don't have answers in Practical Signal Processing by Mark Owen. What is the author looking for here? A mathematical proof? 2.1 A cosine wave of frequency f is sampled at $t = ...
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Ideal sampling - question about the 1/T scaling factor

Sources discussing spectrum of sampled signals (under 'hypothetical' IDEAL SAMPLING condition) show that the original message spectrum gets replicated at integer multiples of the sampling frequency. ...
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Continuous-time RNN and Shannon sampling theorem

The most-used discrete-time RNN equations used in Deep Learning these days are those of Elman: I have seen two very different continuous-time version of these, with different justifications. The most ...
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Question About Sampling White Noise

Assuming that we have a continuous signal $v(t)$ $$v(t) = \int_0^t g(u)\, \mathrm du\tag1$$ where $g(t)$ is white noise.Then take the derivative of it. $$\frac{\mathrm d}{\,\mathrm dt} v(t) = g(t)\...
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Getting SNR of reconstructed signal in MATLAB

I am trying to run code to compare the efficiency of various basic sampling methods such as ideal sampling, natural sampling and so on. I want to then use average power to see how accurate the ...
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Determining timing error for sampling

I am writing a small program for sampling a series of sensors on an Arduino. The sampling process is not 100% perfect, depending on how many sensors I am reading, the actual difference between two ...
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What's the advantage/disadvantage of oversampling followed by decimation, verses sampling at the correct rate to begin with?

I read somewhere that oversampling somehow reduces sampling noise? How to quantify the reduction in noise? and why would it reduce noise if you are decimating the oversampled signal. What's the ...
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Range of updated/new time axis after upsampling? [closed]

I am reading the book "Signals and systems laboratory with MATLAB" by Alex Palamides and I am reading system properties on pg 154 of the book but I am confused about an example shown in attached photo....
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relation between Nyquist sampling theory and regression

Regression is mainly about estimating a function when only a finite number of samples of the function are available. Theories usually care about asymptotic performance as the number of samples tends ...
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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 (...
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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 ...
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Intuitively, why is the comb function the sampling function?

The comb function can be used to sample a continuous signal. The comb function is defined as follows $$ C_T(t) = \sum_{k=-\infty}^{\infty} \delta(t - kT) $$ where $\delta$ is the Dirac function, ...
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Understading sampling theorem and aliasing

A real-valued analog signal with a flat spectrum between f = 0 Hz, and fmax is sampled at a sampling frequency fs = 24 kHz. The sampled signal is then processed with an ideal lowpass filter with ...
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Ideal sampling using sinc funcion

Let $ x(t) $ be a bandwidth limited signal such as $ \forall |\omega|>\frac{\pi}{T} : X^F(\omega)=0 $ while $ X^F(\omega)$ is the signal's Fourier Transform. Let us denote $y[n]=\int_{-\infty}^{\...
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What Does 'Zero Order Hold' and 'First Order Hold' Mean?

While studying the Image Magnification in spatial domain, I have come across this definition of Image Magnification by Replication: Replication is a zero order hold where each pixel along a scan ...
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Alignment of 2 Set of Samples from Different Sensors

If we measure the heart rate of a subject with two different devices, which have big different sampling rates then how we can compare their outcomes. For instance, one of the devices has the sampling ...
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Precise 5th and 7th harmonics of a sampled sine wave

Does anyone know in decibels (to 1/100th of a dB) what the theoretical 3rd, 5th and 7th harmonic of a 0dB fs 24-bit (i.e. full-level; 0dB = -8,388,607 to 8,388,607) sampled sine wave without dither ...
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Multiple different length Windows for high resolution realtime FFT

I am looking at trying to achieve a 'realtime' (as quick as possible to acquire, process and present data) FFT application to analyse audio. I have setup my app to acquire a set of samples, apply a ...
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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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histogram bin size vs. data sampling rate

I have a set of numerical signals that give me a set of zeros calculated based on some numerical procedure. I make a histogram of those zeros. Here, a following problem arises: If the histogram ...