Questions tagged [sampling]

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

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27 views

Reconstructing function from samples

Assuming I have sampled my function with frequency above nyquist frequency, using the sampling theorem I can reconstruct my original function from the sampled values. Let's assume though that I change ...
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What is reference sample in angle of arrival (AoA)?

I'm studying Bluetooth direction finding. The antenna sent I/Q data sampled start with first eight samples as reference sample and ninth sample began with sample data. Now I can calculate angle using ...
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1answer
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Spectral function value of a frequency above the nyqist limit

this was the question on my today's exam on signals and systems: *We have a continuous function $f(t)$. Its value of the spectral function at an angular frequency of $8000\pi\ rad/s$ is $\frac{1}{...
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Sampling with Rectangular Pulse and Nyquist Condition

The classical Nyquist theorem assumes that the sampled signal is obtained by multiplying the signal with dirac-delta functions separated by width 1/f_sample or less. Given such sampling we can ...
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2answers
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Oversampling for Synthesizer

I am in the early stages of learning DSP and am writing a simple synthesizer. I want to dabble in oversampling and am following this guide: https://www.nickwritesablog.com/introduction-to-oversampling-...
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Weird crackling during audio playback - web audio api

I am using Web Audio API + extended Karplus-Strong algorithm to generate plucked string sound and play it. The problem that I face is sometimes there's a weird crackling sound/thump when playing some ...
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Aliasing in continous-time signal

I have the following signal and it was plotted with a sampling frequency (Fs) of 5Khz and F0 was then varied for 0.5Khz, 2Khz, 3Khz, and 4.5Khz. I obtained aliasing when F0 = 2Khz and 3Khz only. ...
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1answer
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Why is the bandwidth of each ZigBee channel in the 2.4GHz frequency band 2MHz, while the sampling interval of the ZigBee receiver is 0.5us? [duplicate]

From the Wikipedia, the XBee paper, the BlueBee paper, and the WeBee paper, I learned that: In the 2.4 GHz band, the bandwidth of each ZigBee channel is 2 MHz. For receiving a signal over one of ...
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How to visualize frequency domain of signal with multiples of $f_s$?

Is it possible to visualize signal in frequency domain for frequencies bigger than $f_s$? I'd like to get the plot of some example signal like that: I tried to create some signals in ...
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One subcarrier lost after using scipy resample in an OFDM system with multipath channel

I simulate with Python a simple OFDM communication chain with a multipath propagation channel and no noise. Here are the details: Generate 10k independant batches of 128 random 4-QAM symbols. The 128 ...
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Undersampling in GNU Radio

I'd like to implement a FHSS receiver in GNU Radio, using a USRP B210. The total bandwidth of the signal is about 30 MHz, with each message having a bandwidth of about 200kHz. When I attempt to ...
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Noise from irregular sampling pattern

In this paper the author says By using an irregular sampling pattern and filtering the irregular samples to create the pixels, featureless noise is produced from such high frequencies rather than ...
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449 views

How to calculate sample times when the clock rate is not divisible by the sample rate

I need to sample an ADC at 4096 * 60 = 245760 times per second, but the system clock is 200 MHz. This gives a sample period of 813.80208333.... clock cycles. I've determined that I can achieve the ...
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3answers
49 views

Sampling Theorem for band limited continuous spectrum signal

For example a signal $y(t)$ contains infinite number of sine waves each with varying finite random amplitudes and random frequencies between $-B$ to $B$. Can this signal be reconstructed when sampling ...
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1answer
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Chroma subsampling calculating bandwidth

How do I calculate the bandwidth required to transmit a UHDTV signal with a frame size of 3840 x 2160 at 50fps with a sampling rate of 8bits/sample?
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1answer
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How to find point of inflexion of a digital signal?

Let's say I would like to find a point of inflexion of a digital signal which has been gathered via sampling of a continuous time domain signal with sampling period $100\,\mu s$. The digital signal ...
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2answers
72 views

Why do we need to add an anti-aliasing filter?

For example, we need the frequency range of $0\to3000\text{hz}$ to represent a speech signal. The book, Digital Signal Processing (Proakis), stated that we need a low-pass filter to admit only the ...
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ADC sampling of incoming signal and aliasing effect [duplicate]

I know from the sampling theorem, that the signal frequency $f_{sig}$ shouldn't exceed 0.5 of sampling frequency $f_{samp}$. I decided to have a look at it and tried for example $f_{samp} = 50 $ $kHz$ ...
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What should be a sampling frequency, that we could add two signals?

I got a code in Matlab: ...
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1answer
57 views

misunderstanding of spectral leakage

I want to understand spectral leakage. I understand that whenever we feed $N$ time-samples of a periodic, continuous, signal into a FFT algorithm we are multiplying in time-domain the true periodic, ...
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217 views

Quantization error standard deviation

Here I found that "pure" quantization error standard deviation of the signal is $1/\sqrt{12}$ of LSB. Where does it come from?
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Misunderstanding of Nyquist sampling theorem and minimum sampling rate

I sample my time-domain (TD) signal using a distance between time-samples of $\delta = (t_{max} - t_{min}) / N_t$, where $N_t$ is the number of samples taken. The sampling rate is $1 / \delta$. I have ...
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Why does the amplitude of a reconstructed sine wave change based on its phase?

Let's say we have some 5 different sine waves, each having a frequency of 10 Hz but differing in phase i.e. 0, Pi/6, Pi/4, Pi/3, and Pi/2. Each of these signals is sampled at twice the signal ...
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What sampling frequency should I use if Nyquist is not available?

I have the following homework question that confuses me: We have an audio emitter that can emit two signals: It either emits a sine wave at 23 kHz or it emits a sine wave at 25 kHz. The receiver has ...
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1answer
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The minimum frequency for signal modulation

I have a signal sampled with frequency 10 kHz. My spectrum is 1 kHz. As far as I went, according to the Nyquist theorem I can module the signal with max. 5 kHz (1/2 of sampling frequency). What's the ...
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Sample rate vs noise floor in power spectral density measurement

I am trying to measure the noise floor of my picoscope. I want to generate a PSD in volts per root hz that I can compare with specs from other equipment, e.g. a preamp. I gathered some data from my ...
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1answer
93 views

How do we equate the signal energy before and after sampling?

I have a band-limited signal and sample it at sample rate of $f_\mathrm{s}$. By taking the continuous time fourier transform, I will see copies of the same signal at $n\cdot f_\mathrm{s}$ where $n \in ...
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Filter Synthesis Formula to implement ZOH

$$h_n = \frac{1}{2\pi}\int_{-\pi}^\pi H_d(\omega) e^{jn\omega}\,\mathrm d\omega$$ I am attempting to design a FIR filter using the formula above for coefficients. Where $$H_d(\omega) = \frac{\sin \...
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2answers
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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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1answer
132 views

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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1answer
79 views

Noise Variance and Sampling in the Linear Regression Context

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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2answers
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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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1answer
52 views

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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1answer
77 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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1answer
49 views

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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1answer
24 views

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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1answer
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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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1answer
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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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1answer
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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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5answers
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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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1answer
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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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0answers
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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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1answer
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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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2answers
103 views

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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2answers
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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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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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