Questions tagged [sampling]

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

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281 views

Noise PSD and sampling rate relation

Let's consider generating samples of a random process like white Gaussian noise (AWGN). Let's assume I am generating $N$ samples of AWGN with variance $\sigma ^2$ in MATLAB by using randn() funtion i....
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596 views

Nyquist frequency and DC

Im studying the DSP book by Steven W. Smith. On page 41 he covers the Nyquist frequency. He makes up an example by writing the following. ... consider an analog signal composed of frequencies ...
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149 views

about sampling frequency

I am trying to make a DFT on a signal with frequency f=50 MHz main component plus some noise. As far as I know if I sample it at F=100MHz I should be able to get a proper plot of the DFT since F=2f ...
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63 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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63 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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55 views

IQ Sampling and Oversampling Differences? *Confused*

Two different thought process that produce two different alias band calculations .... What concepts are these? If I have two 1 GHz ADC's and they sample with 90 degree offset (A comment said this is ...
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4answers
47 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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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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1answer
54 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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64 views

How do Anti-Aliasing Filters filter the signal?

I have programmed a anti-aliasing filter that uses the fourier-transformation and makes a perfect cutoff on my desired cutoff frequency for downsampling without aliasing. I have read about other ...
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15 views

Sampling points on a face of a human body mesh

Is there a known shape analysis technique to sample points of a not necessarily naked human body mesh (more specifically the head part). The goal would be to randomly sample (uniform distribution) ...
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63 views

How to make low pass filter using frequency sampling method?

https://www.allaboutcircuits.com/technical-articles/design-of-fir-filters-using-frequency-sampling-method/ So there is two main equation: I wish to filter out frequency $\le 10000Hz$, for example. ...
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Canceling interference (such as harmonics from out of band source )

I have a vague-ish question, if it makes sense: The desired received signal (from source S1) was carried at 3 GHz passband carrier frequency, with bandwidth 20 MHz. It was interfered with by the 3rd ...
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79 views

Sampling period

I started it but didn't how to continue , any help ?
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149 views

How Is a Signal Changed After Sampling?

I can't understand sampling signal mathematically. for example $x(t) = 2\cos(100\pi t) + \cos(300\pi t)$ and I know I should use sampling frequency $300\textrm{Hz}$ to sample this signal. and after ...
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82 views

FFT of white noise with different sampling rate

I have a question on how I should interpret the white noise power level (noise floor) obtain from FFT for different hardware sampling rates. I realized if I sample the same noise at different rates (...
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29 views

Perform frequency analysis on grouped pulses

I have a system which consists of individual pulses grouped in trains. The trains have a frequency of 10 Hz, with a timing precision of sub ns. The pulses have a frequency of 2.2 MHz with a timing ...
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37 views

does aliasing occur always if i sample a vibration in real world applications?

I was reading about the aliasing effect and nyquist. I understand that aliasing effect occurs if the sampling rate is lower than twice the maximum frequency in the signal I want to sample. So I was ...
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Nyquist theorem vs sampling theorem vs shannon sampling theorem?

Is there any difference between these three?or these are just three names of same theorem?
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990 views

Use of the Dirac delta as a sampling operator

As we are all taught in signal processing classes, the Dirac delta is not a normal function but a generalized function. It is sometimes defined as either the limit of some normal function whose ...
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237 views

Sampling Theorem and Signals Explained to a Mathematician

Let $f:\left(-\frac T2,\frac T2\right)\to\mathbb{R}$ for some $T>0$. The Fourier coefficients of $f$ are $$\left\{\begin{matrix}a_0&=&\displaystyle\frac 1T\int_{-T/2}^{T/2}g(t)\;dt\\a_k&...
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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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1answer
1k views

Sampling Rate Effect on Quantizer SNR

I am currently reading the 'Coding' chapter on Rabiner & Schafer's Book on speech processing. In one of its exercises, the reader is given a simple A/D converter using 16-bit uniform ...
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50 views

Zone Plate Reconstruction

I am trying to reconstruct the Zone Plate image and am struggling to remove the last remaining aliasing. ShaderToy: https://www.shadertoy.com/view/wdGGWK In the shader above you can see that I am ...
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45 views

Torque signal fft

I have the following torque signal picked up with a 10.240Hz sampling rate from a testbench. I am studying its fft which I create on Octave with the following code: ...
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1answer
39 views

Build an inverse model for a train of gaussian pulses

I have a stationary signal from a train of Gaussian pulses. My sampling window is too wide (cannot be reduced). In the example 1 ms. So it is not possible to clearly distinguish one pulse from another....
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1answer
37 views

Phase difference measurement of a 100 kHz tone

I would like to measure the phase difference of a 100 kHz tone. The tone is transmitted and then received. The received tone is sampled using an 1 MHz 12 bit ADC(IQ) and the SNR is at least 35 dB. ...
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187 views

Reconstructing/interpolating small regions of a bandlimited signal by taking the fewest possible samples

I have a signal which is bandlimited and can be sampled at arbitrary continuous positions. The value at any position is given by an expensive computation. I need to do some further computation on ...
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932 views

Compressive Sensing vs. Sparse Coding

There apparently are different terminologies used to refer to the same field called "compressive sensing" such as (see this wiki page): compressed sensing, compressive sampling, or sparse sampling. I ...
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38 views

Interpretation of sample rate

I'm a little confused about the sample rate: If I have an audio file that was recorded with a sample rate of 48kHz, this means that there are 48,000 values per second in this file, right? So when I ...
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21 views

Doubt in Frequency Modulation code

While searching for something FM, I came across this code. I am not able to understand a particular line of code. I have written a comment against that line of code. ...
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1answer
70 views

What does the frequency band mean when it comes to finding aliases?

The time signal which i'm trying to find the aliases for is: $$x:{\mathbb R}\rightarrow {\mathbb R}\\\ x(t)=\cos(50t) +2\cos(70t).$$ If the sample period is $T_s = \frac{\pi}{60}$ then according ...
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Sample-rate, filtering, digital-filtering and aliasing

I am strugling with a question that I hope someone can help me with. I am recording single molecule events which I detect is picoampere square deflections. I wish to use as gentle low-pass bessel ...
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25 views

removing noise using Scipy.signal.butter:

I am going to remove the noise from a brain recorded signal. It was a continuous recording and with sample rate=30kHz, it was digitized. So now it is a digital signal. I have written the code here ...
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1answer
48 views

Trouble with understanding moving average filter as an oversampling filter

I am struggling with understanding how an moving average filter can increase ENOB in a given sample. I wrote a test for a simple MA (moving average) filter in matlab. The algorithm to create new MA ...
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1answer
435 views

Bridging CTFT and DTFT for a cosine

I'm trying to understand how I can start from the CTFT of a signal and end up with a DTFT. For example if I take a basic example: $$\begin{aligned} x(t) &= \cos(\omega_x \cdot t) = \frac{1}{2} \...
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1answer
59 views

sampling a continuous time signal using MATLAB?

I have a continuous time signal $x(t)=cos(2 πft)$ where $0\leq t \leq 2$. I want to plot discrete time signal $x(n)$ where $0 \leq n \leq 19$ for sampling frequency 100 Hz and signal frequency 10 Hz. ...
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1answer
32 views

Recoverable continuous function after average sampling

I have a personal interest in this question, but I don't know if it is unfounded. Suppose I have a continuous function x (t), which is sampled using an average sliding window, which performs a ...
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2answers
63 views

Why is the digital frequency highest at $\pi$ and what does it mean in terms of analog frequency? [duplicate]

I can't seem to comprehend why the digital frequency is highest at $\pi$. I know the relationship between the digital and analog frequency is given by: $$\omega = 2\pi\frac{F}{F_s}=2\pi f$$ Where $F$ ...
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94 views

Sample Rate & Highest Frequency

Would I be right in saying that if a signal was sampled every 0.2ms, when converting it to digital. The sampling rate would be 5000(Hz)? How would I go about working out the highest frequency it ...
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1answer
66 views

relation between DFT to CTFT

The signal $$x(t)\;\;\;\;0\leq t\leq 0.2s $$ We know that the CTFT of $x(t)=0$ when $|w|>2*\pi*10^4$ We sample $x(t)$ in sample space of $$T=25\mu s$$ or $$F_s=1/T=40000Hz$$and we get a series ...
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3answers
71 views

Poisson summation formula and periodic summation of Fourier transforms

One of the forms of the Poisson summation formula is $$ \sum_{n=-\infty}^{\infty} T\cdot x(nT)\ e^{-i 2\pi f T n}\; {=} \; \sum_{k=-\infty}^{\infty} X\left(f - k/T\right),$$ where $x(nT)$ are ...
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49 views

find the maximum of the DFT of sampled signal

The signal $$x(t)=\cos(10\pi t+\phi)+\cos(20\pi t)$$ is sampled with a sampling frequency $F_s$ as $25 \mathrm{Hz}$ where the phase $\phi$ is unknown. Sampling the continuous time signal $$y[n]=x(nT)$...
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100 views

Fourier Like Spectral Analysis with Uneven Intervals and Redesigned DFT Matrix

I intended to use a discrete Fourier transform (DFT) on a time series sampled at uneven intervals. What I did was to calculate a DFT matrix where the elements are the values at the uneven locations ...
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1answer
62 views

Discrete time aperiodic signal: Concept of frequency?

Is concept of frequency to a-periodic signal whether it is continuous or discrete time is valid? I am bit confused, since discrete time sinusoids have frequency $-\pi<\omega<\pi$ or $-\frac{1}{...
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2answers
14k views

What is the difference between cubic interpolation and cubic “Spline” interpolation?. How to use it for upsampling purpose?

After considering a couple of advices and suggestions for upsampling techniques here, I finally converged to use the cubic interpolation technique to estimate the voltage values corresponding to ...
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54 views

ADC sampling rate implications Matlab/Simulink M-PSK modulation

I am trying to find a way to evaluate what would be the minimum sampling rate used in a modulated waveform using matlab / Simulink. The real scenario would be let say a M-PSK waveform of Y bandwidth ...
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1answer
42 views

Choosing right cut-off frequency for a LP filter in upsampler

I'm implementing a upsample function in Matlab but it's not perfect right now,for reasons I'm not sure. Here is my code: ...
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390 views

Are resolution increase and noise reduction from oversampling mutually exclusive?

Oversampling a signal means sampling it with a significantly higher sampling frequency than the Nyquist rate. As far as I know, there are three advantages: Easier design of anti alias filter Increase ...

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