Questions tagged [sampling]

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

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Trouble understanding how image digitization works

Quoting Image Processing, Analysis, and Machine Vision, 4th ed. An image to be processed by computer must be represented using an appropriate discrete data structure, for example, a matrix. An image ...
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Fourier transform of an impulse-train sampled signal

I'm trying to calculate the Fourier transform of an impulse-train sampled signal in two differnt ways but I end up with different results. Impulse-train sampling of a continous signal $x(t)$ with ...
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Noise variance and sampling

I am new to signal processing, so please bear with me. My question applies to any general problem of estimation from noisy measurements but I will like to understand this through a problem given here. ...
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Why do the lengths of the sampled signals $x_1, \: x_2$ have to be $\text{length}(x_1)+\text{length}(x_2)-1$?

We know that convolution in time is equivalent to multiplication in frequency (Fourier). $$x_1(t) \ast x_2(t) \leftrightarrow X_1(\omega)X_2(\omega) \tag1$$ However, for a sampled signal, this ...
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Random projection with compressive sensing and hashing algorithms

I read that Random Projection matrices can be used in both Compressive Sensing and Locality Sensitive Hashing. I need simple explanation for the difference between applying Random Projection in both ...
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Why are there copies of a signal in the frequency domain? [closed]

I only know about this from images and some videos and articles I've read, but I haven't managed to find an explanation. It only says they exist. This is what I mean: Blue is the frequency domain of ...
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61 views

How to upsample voice properly?

I have a low quality 24 kHz mp3 voice and I'd like to upsample it to 48 kHz for farther mixing with another ...
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Synthesizing guitar sounds given a frequency

I'm trying to build a web app which plays a sequence of notes. The notes should have a timbre of different instruments. For now I only concentrate on a guitar synthesis. I'm using Web Audio API for ...
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Infinity values in statistical analysis of minute frequency data

I'm trying to extract statistical features from power spectral density values in Python. My data is actigraphy data with sampling rate 1/60 Hz (once per minute). This is a sample from my data, "...
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Sampling frequency after aggregations

I have accelerometer signal, which is preprocessed by the actigraph on-device. Original sampling rate is 32 Hz, but activity count is summed for every minute, so I have a signal with 1 measurement per ...
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Running a signal through a circuit with some odd components

I am studying a course in signal analysis and systems. Currently we are looking at aliiasing, samplig,DTFT and reconstruction. I got stuck on an excercise. For the in signal $x_{a}(t)=2\cos(2\pi F_{0}...
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Why it is possible to sample a discrete signal from a sequential signal but not a sequential signal from a discrete signal?

Why it is possible to sample a discrete signal from a sequential signal but not a sequential signal from a discrete signal? I avoid making any assumptions not to write something wrong.
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Why does twice the sampling rate (Nyquist Theorem) seem inadequate?

I was told in my electronics course that "to reproduce a wave, we need to sample it at least twice every period." If I take this to be literally true, then a sine wave with only 2-3 samples ...
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Varying shift between microphone data

I had given a sine wave of frequency 2kHz as input to two microphones placed near to each other. The data grabbed by two microphones are then plotted in MATLAB and it was found out that the initial ...
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How to determine sampling rate of a lock-in amplifier?

I am trying to figure out the sampling rate of a lock-in amplifier and how it is related to the time constant. For example, imagine measuring sinusoidal waves at $1$, $5$, $10$, and $50$ Hz ...
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Recovering from exponential discrete-time signals

The spectrum of the discrete-time signal $x(n)=e^{-2n}$ is sampled at frequencies $2\pi\frac{k}{2014}$ for $k=0,1,\ldots,2013$. Can the signal $x(n)$ be uniquely recovered from these 2014 samples? ...
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Which of the following sampling methods can be used to sample x(t) such that this signal can be uniquely recovered from its samples?

Assuming that a continuous-time $x(t)$ having its frequency content in the frequency band $1612\leq|F|\leq2015(Hz)$ is sampled with the sampling rate $Fs=806$ samples per second. Which of the ...
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How do I detune an audio sample by 1 hertz up or down from a copy of it

I have a program that can take a waveform, such as a sine wave or sawtooth wave and detune it with another waveform that is slightly sharper or flatter. It takes the frequency of said waveform and ...
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Changing sampling frequency of SDR

Here is the block diagram for RTL-SDR which is taken from Software-Defined Radio Using MATLAB, Simulink, and the RTL-SDR: I think it well explains the basics of RTL-SDR but I have multiple questions. ...
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Can we have an analogous sampling theorem for quantization?

Sampling theorem tells us how we can sample a continuous signal such that we can reconstruct it without any errors, or without losing information. Quantization, on the other hand always results in ...
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What should be my sampling frequency for a peak detector output where it is extremely important for me to capture the first time the peak occured?

Following is the output of the peak detector: The amplitude is not important to me, however the time when the peak occurs is extremely important. So my microcontroller will have an algorithm like ...
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226 views

Nyquist frequency isn't working

The situation is that I have a signal with linearly increasing frequency, $$\text{sin}(2\pi\omega(t)t),$$ where $\omega(t)=a+bt$ for some $a$ and $b$, and we constantly sample at one point per second ...
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34 views

Signal to noise ratio (SNR) of a CW signal

I understand the formula SNR = 6.02N+1.76 for a N-bit ADC which quantizes a modulated tone sampled at twice the BW. I am trying to understand what the same equation would be for a unmodulated CW tones ...
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Mitigating high-frequencies after sampling

I have a dummy signal that I am sampling at $T = 100 \ \mu s$. According to the Nyquist frequency, I can identify frequencies up to $\pi/T = 31416 \ rad/s$, as we can see in the FFT of my signal (blue ...
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Can we use Gardner timing error detector for multi level QAM or OFDM systems? [duplicate]

Sampling frequency offset (SFO) between the transmitter and the receiver in any system causes a gradually increasing timing error which is seen as an increasing phase rotation (function of time). In ...
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GNURadio signal degradation *above* Nyquist rate

I am going through the basic tutorials for GNURadio, and I have a question related to the sample rate tutorial. In it they demonstrate the degradation effects of sampling at too low a sampling rate. I ...
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Does Sampling frequency come into picture in Samples generation for DAC to generate sinewave (analog signal with particular frequency & amplitude)?

I'm generating samples for dac in STM32. sin(2pii /N)*4096/2. This is the formula I'm using. How to I come to know sampling frequency? Whether sampling frequency comes into picture?
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How is sampling affecting this sine wave?

I am trying to create a sine wave in python, but when I graph it, it looks like this: here is the code I used to make the signal: ...
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Does summing two audio samples affect sampling rate?

Original Post: Electronics Stack Exchange ("Why is my frequency being effectively doubled?") I'll try to explain everything with detail as this is one will be a hard one to explain. ...
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62 views

Dealing with normalized cut-off frequencies larger than 1.0

I am trying to create an FIR bandpass filter in python using scipy with the following characteristics: $$f_{c_{low}} = 310\,Hz$$ $$f_{c_{high}} =600\, Hz$$ giving me a bandwidth of: $$Bandwidth = f_{...
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Sampling Noise Given Power Spectral Density

I am trying to write a Monte Carlo physics simulation which involves, given a power spectral density, sampling rate, and total number of samples, generating noise with such a power spectral density. I ...
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2FSK implementation with VCO GNURadio

I am fairly new to GNURadio. I am trying to generate a 2FSK with minimum frequency shift. Instead of multiplying with a 8MHz complex carrier, I directly use VCO to generate two frequencies. One at 7....
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Where can I get the file l1eq_pd.m?

To recover the original signal when compressive sensing is used, we get an error, to avoid the error, we need to modify the l1eq_pd.m file. How to go about it? Where can I get this file in Matlab?
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Aliasing in Doppler Radar

my book about RADAR says that: If a Continuous wave radar sends a sine wave at frequency $f_T$ to a moving object (at speed V), a frequency $f_R$ is received. Their difference is called Doppler ...
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Why symbols have to be upsampling, if the symbol rate and sample rate is same what happen?

In digital modulation process, after constellation mapping and before pulse shaping, the symbols are upsampled with the number L(samples per symbol). At this moment, why symbol have to be upsampled, ...
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How to reconstruct original signal from sampled signal?

My original signal as f1=2; f2=5; fs=100; Ts=1/fs; t=0:Ts:1; xt=cos(2*pi*f1*t)+cos(2*pi*f2*t); figure plot(t,xt) as shown below figure. and my sampled signal ...
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Clock recovery using Mueller and Muller adds noise affecting EVM or SNR (Two cases - GNU Radio & Python code)

The implementation of the Mueller and Muller clock recovery that I am seeing adds a large amount of 'noise' or degradation to the Error Vector Magnitude (EVM) to the symbols on the constellation. This ...
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38 views

FFT requirements of real time signal from sensors

I have an electrical current sensor which generates measurements every second. I want to calculate the FFT of this signal. Since my real-time values are received every second, I think that the fastest ...
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Speed measurement calibration

I have a sailing yacht where speed is measured using a peddle wheel. It measures speed through water (STW). This measurement contains a measurement error whose magnetude is dependend on both speed (it ...
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59 views

How to perform a phase recovery for higher order modulation schemes

My objective is to demodulate the signals with different modulation orders and schemes. In particular, I want to recover the phase first. Let us say, my signal looks like in the constellation below . ...
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92 views

Sampling with an alternating phase offset

Suppose, I sample a signal $z=\mathrm{e}^{\mathrm{i}\omega t}$ alternatingly in $I=\mathrm{Re}(z(t))$ and $Q=\mathrm{Re}(\mathrm{e}^{\mathrm{i}\alpha}z(t))$. Thus my data array contains $$\texttt{data ...
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Train of impulses in frequency domain

Why compressing a train of impulses in time domain produce a wide-spaced train of impulses in frequency domain and vice versa? i want to know the intuition behind that.
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Sampling and Demodulation question

if I have an analog modulated signal with a DSBSC modulation (modulation index 100%) as an input in my receiver and I want to convert it to a sampled signal, do I need to demodulate the signal (with ...
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Nyquist Frequency and Window Length

The Nyquist theorem states that the sampling rate must be twice the highest frequency to be observed. How does the length of the interval play into this relationship? The main resource that I found ...
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How to find peak value of an analog signal efficiently after sampling in the digital domain?

I have a bandlimited analog signal for which I want to find the peak value in real time. The signal is sampled and processed digitally at just enough sampling rate. Since the peak of the analog signal ...
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Does the Shannon theorem not apply when the amplitude of a wave is changed faster than half the time period of the wave?

Shannon's version of the sampling theorem states that if a function contains frequencies all strictly less than $B$ hertz, then it is completely determined by giving its ordinates at a series of ...
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QPSK demodulation

My objective is to demodulate QPSK signal. At this moment, my constellation in the best case looks like in the picture below: and the corresponding eye-pattern: Eyes are completely closed, which ...
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What is the difference between sampling over $-4\pi$ to $4\pi$ and 0 to $8\pi$

I see no difference in magnitude, but the phase plots vary significantly while using NumPy and MatPlotLib to plot. Looking at the phase plots, I feel like I'm missing something important. Also, I'm a ...
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63 views

Filter to eliminate a 60 Hz frequency range

I have a analog signal that is converted into a discrete-time signal with an ideal A/D converter with a sampling frequency $fs$. The bandwidth of the signal of interest is $1 kHz$. The resulting ...
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Rate transition block in simulink

My model is operating at a sampling interval of $\frac{1}{f_0 \times N \times L_{maf}}$ s, (using a fixed point iterative method), now i want the output of my model to be at a sampling rate of $ f_0 \...

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