Questions tagged [sampling]

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

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Aquila DSP C++ Library - Wave file FFT analog frequency off by factor of 4?

I'm working with the Aquila C++ DSP library. I'm computing the FFT of a wave file (16 bit depth, single channel, 44100 sample rate). I am using a window size of 16384 to calculate the FFT spectrum. I'...
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48 views

Cancelling out known signal with sampling offset

I would like to cancel out a known audio signal at my receiver. Specifically at my transmitter I am playing a song, and at my receiver I am recording it. Both transmit and receive sampling rate is 44....
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117 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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1answer
46 views

How to describe correlated noise after the signal is oversampled?

The Gaussian noise in discrete signal models is usually assumed to be independent and identically distributed variables (i.i.d.). Does this mean that the signal must be sampled with the sampling rate ...
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49 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
129 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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57 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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90 views

Digital to analog aliasing or mirror query… DAC can output negative frequency?

Using a clock Fs = 1 MHz. The Digital to Analog (DAC) can make frequencies upto 500 KHz. 500 kHz to 1 MHz is an alias? Or is it called a mirror?? Is aliasing a concept only on the ADC and sampling ...
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22 views

Nyquist sampling theorem / Nyquist - Shannon theorem evaluation over M-PSK

I am trying to simulate an M-PSK Tx-Rx System on Simulink and analyse what the effect of sampling rate reduction would have on it. More, particular I am trying to prove what Nyquist sampling theorem ...
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1answer
61 views

Variance of a signal

How to calculate the variance of noise samples modeled as follows: $n_a(t)$ is a Gaussian zero-mean white noise process with (two-sided) power spectral density $\frac{N_0}{2}$. $n_a(t)$ is passed ...
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19 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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1answer
59 views

Why is my filter unstable and self-oscillating in this case?

I am using resonant bandpasses to simulate modes of guitar/piano strings for audio synthesis. While attempting to introduce coupling effects I have encountered a problem. I will illustrate with some ...
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how a signal for which calculate RMS can be filtered and have a fast settling time?

i designed a sinusoidal pwm amplifier (3KHz to 20KHz) that regulates its output voltage reading the RMS value of output current. The RMS is obtained squaring the signal sampled by AD converter @...
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66 views

Sampling period

I started it but didn't how to continue , any help ?
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2answers
56 views

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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1answer
46 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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365 views

relationship between energy and sampling rate

Excuse my silly question, but i really want to know does changing the sampling rate affects the energy (bandwidth) of a signal? therefore improves cross correlation output?
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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
21 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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1answer
40 views

What is the difference between t=n*Ts sampling vs impulse train sampling?

I know that if I sampling with impulse train so I get in the frequency plane X(f)*h(f) (when x(f) is my signal, * means convolution and h(f) is fourier transform of impulse train). what the ...
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180 views

Transform a Continuous Time Differential Equation of a Low Pass Filter to Discrete Time

Assuming I have a linear differential equation of first order low pass filter: $$RC*y(t)'+y(t) = x(t) $$ And Assuming i know now that the input x(t) is being sampled at a rate of $T_s$ how can now ...
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1answer
44 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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29 views

Signal to Quantization noise problem

a full scale signal of bandwidth 5 khz is sampled by an 10-bit ADC at a sampling rate of 2 Msa/sec calculate the Signal to Quantization noise of the resulting DT signal repeat for a 14-bit ADC at ...
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FFT first frequency

I have some problems understanding FFT. If I know Fourier analysis frame (1024 samples) and sample rate (48 000 Hz), how can I find the first frequency of harmonic sines and cosines?
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Band-limited signal recovery with finite bit depth

The sampling theorem tells us that a signal with no frequencies above $f$ can be completely described by sampling it a rate of $2f$. However, the theorem makes no reference to quantization, and so I ...
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DTFT based Frequency Sampling

H($e^{jw}$)= 1, |w| < $\pi/2$ and 0, $\pi/2$ <= |w| <= $\pi$ I took M equally spaced frequencies from 0 to $2\pi$. If we assume h[n] to be causal, $H(e^{jw})$ should have some phase and it'...
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Looking for a analytical formula to compute the central frequency of a signal analyzed by a discrete wavelet at a given scale

I am reading this paper by Han et al. (2014). In this article, the authors extract detailed information from geomagnetic data sampled at 1Hz using a daubechies 5 (db5) wavelet: they reconstruct the ...
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129 views

Unexpected Result When Using Sinc Interpolation

blue is how I tried to sinc interpolate. why would something like this happen?
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63 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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42 views

Analog-to-Information Converters?

In Analog-to-Digital Converters(ADC), the signal is first sampled at a rate higher than or equal to the Nyquist, then quantized and encoded. In Analog-to-Informations (AIC), the sampling and ...
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1answer
30 views

Sampling a signal with varying frequency

Question I'm trying to figure out the sampling rate for my ADC to sample essentially signal essentially of the form: $$y(t) = \sin(\max(t, \omega_{max})\times t) + n$$ where $n$ is noise. Context ...
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1answer
77 views

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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1answer
72 views

Real-time DAQ (Data AcQuisition) device and filtering of voltage signals in audio frequencies

I'm working on a frequency mixer project in which two analog voltage signals at two different frequencies (each <5 kHz) are considered. I'd like to add the two fundamental frequencies and return an ...
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50 views

with given Sampling rate, what max frequency human voice can be captured?

I'm new to signal processing and sampling rate, I was asked interview question related to this. This is the exact question asked: With 8Khz of sampling rate, whats the max frequency that human ...
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1answer
103 views

When calculating SNR, is noise included in signal?

Given a signal $x(t) = s(t) + n(t)$ where $s(t)$ is the desired signal voltage and $n(t)$ is the noise, should the signal to noise ratio of this signal be 20log(xrms/nrms) or 20log(srms/nrms)? i.e., ...
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31 views

$x[n]$ after sampling of $cos(16\pi t+\phi)$ at 12kHz

I'm not sure what the question really means, so this is just guesswork. I think options 1 and 4 can be ruled out as $w_0<\pi$. The CTFT of $cos(16\pi t+\phi)$ has two spikes at $16\pi$ and $-16\...
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Find integral of DTFT after sampling (Graph of CTFT given)

So for the first question: If this is sampled at 10kHz, then the amplitude is scaled by 10000. In the DTFT, the frequency 3.5kHz gets mapped to 3.5/10* 2pi=0.7pi. So this point lies outside the range ...
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1answer
35 views

Find $X(j\omega)$ after sampling of $2\cos(2000\pi t)+\sin(5000\pi t)$ at 5 kHz sampling rate

The Fourier transform of the first term has two spikes at -2000pi and 2000pi of magnitudes 2pi for both. The Fourier transform of the second term has two spikes at 5000pi and -5000pi having ...
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37 views

Passing a sampled signal through a filter

I was wondering why is it wrong to use a band-pass filter on a sampled signal? If the signal we want to sample has frequencies up to fmax, we sample it with frequency fs = 2fmax (so that Nyquist ...
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Derivation of Nyquist Frequency and Sampling Theorem [closed]

I have been looking through different sites and questions over the internet about Sampling theory, but couldn’t find the clear definition of how nyquist frequency condition is derived? It would be ...
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2answers
406 views

Compensation for Irregular Time Step for DFT (FFT)

I want to run a clustering algorithm (svm, knn) on the ferquency spectrum data of a temperature sensor that published at irregular times. Here is the temperature data to take the FFT: I got the ...
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1answer
55 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
32 views

Inverse Fourier Transform Dirac impulse with scaled argument

Currently, I am dealing with the sampling problems and I don't understand how to calculate inverse Fourier transform of a scaling impulse function $\textrm{IFT}\{\delta(\Omega T)\} = ?$, $T$ is ...
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2answers
540 views

Where can I find an authoritative (peer-reviewed or textbook) reference to sampling-induced beating?

I presume we are all here well aware about foldback aliasing when sampling signals above the Nyquist frequency; i.e. half the sampling rate. By contrast, the phenomenon of beating occurs when ...
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47 views

A Different Reconstruction Operation

I want to understand what is happening in below operation: Here, x(nT) is sampled signal (say oversampled) and h(t) is its ideal reconstruction filter. As highlighted in the expression, amount of ...
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0answers
56 views

Problem with 1st order PLL update equation

The output of a communication channel is given by: $x(t) = \sum_n{a_n}h(t-nT)$, where $\{a_n\}$ are BPSK symbols, $h(t)$ is the channel response, and $T$ is the symbol period. If there is an ...
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201 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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264 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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1answer
61 views

Conclusions of sampling around Nyquist Rate

I'm trying to understand some results of playing around with sampling around a signal's Nyquist sampling rate. For my example, I'm sampling a $B=5\mathrm{Hz}$ wave over a 1 second period. In the ...
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1answer
64 views

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. ...