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Questions tagged [sampling]

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

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How do MATLAB and/or Python treat $2^n$ samples rule in FFT

As far as I have read, an FFT requires that the number of original data points must be a power of 2. I'm wondering whether the tools like MATLAB or Python which have FFT functions take care of this ...
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23 views

Detecting level in a Pulse Train

Assume I have a square wave pulse train, where each high lasts for H and each low lasts for L seconds. I sample this waveform and have the sequence of numbers. Question is what should be the sampling ...
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artifact identification in irregular-samped data

There is a dataset combined by different datasets a,b,c,d,e. The time intervals are irregular(i1, i2, i3:intervals between a and b, b and c...), but the sampling rate SR in every single dataset is the ...
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88 views

How do I extrapolate a 1D chirped signal?

Following a past question, I'd like to extrapolate a signal like the one below: (red is signal, blue is the the extrapolated ) ...
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1answer
103 views

Convert 96 Khz to 48 Khz audio: is this simple downsampling method ok?

I have an audio signal x sampled at 96 Khz. I have already lowpassed it with a cutoff somewhere between 20 Khz and 22 Khz, so there should be nothing left of ...
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118 views

Reconstruction of a signal from non-uniform samples [duplicate]

So I'm having some troubles with a signal that's been sampled but where the samples don't have consistent intervals. I've been looking into the NFFT (in python) as a starting point but I'm a complete ...
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173 views

MFCC window size at different sampling rates

The general recommendation for window size when calculating MFCC seems to be 20-40 msec. This is most often recommended in a context of 16000 samples per second, so leading to a window containing 320-...
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39 views

What kind of signal reppresents this Power Spectral Density?

I'm sampling 8 bioelectric signals with a embedded board which use an 8-channels ADC (AD7175-8). My sampling rate for every single channel is about 6250 Hz. When move the analysis in the frequency ...
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1answer
104 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: $$ x(t) = cos(\omega_x \cdot t) = \frac{1}{2} \cdot \left( e^{j\...
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72 views

How do ADC/DACs deal with out of sync signals near Nyquist frequency?

Let's say a converter is sampling continuously at 48 kHz and the incoming waveform is a sine wave at 24 kHz... How does it faithfully recreate the waveform if the samples are taken at points that are ...
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1answer
199 views

sampling rate Matlab

I have a rather strange but i thin interesting question. The idea is to gain a better understanding of sampling rate vs frequency shifting when playing audio. The idea is a little experiment: ...
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1answer
64 views

Shannon theorem and zero padding

Sorry if I ask a basic question but I am a bit lost. I have a data set in frequential domain, I need to go to time domain to perform time-gating and then going back to frequencies. In order to do ...
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130 views

Determining sampling rate for signal reconstruction

I want to know how to determine the signal sampling rate required to reconstruct electrical signals whose frequency components are unknown, such as, for example, signals of charge/discharge voltage on ...
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91 views

How to delay an audio signal by 1 microsecond? [duplicate]

I have an audio signal sampled at 44100Hz. I want to delay this signal by 1 microsecond (and maybe even less) for a steganographic purpose. Now if I delay it one sample, the corresponding time delay ...
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66 views

How can I mimic this ADC for a given resolution, sampling rate and input with MATLAB or Python?

I'm quite new to the area so I need help to progress at some point. Basically I have a signed 16 bit ADC which means it maps -10V to +10V range to 16 bit. So the max voltage +10V is 2^15-1 = 32767; ...
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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 Ts.How can I sample the continuous signal by Ts/2 instead of Ts in order to get two ...
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1answer
92 views

Designing an experiment to show blue noise not adding noise below nyquist and not aliasing above

I read this paper from 1983 "Spectral Consequences of Photoreceptor Sampling in the Rhesus Retina". This paper talks about blue noise sampling patterns in the retina and says that: The results (...
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42 views

Can we sample the signal with any period as long as the Nyquist rate is respected

I have a question regarding the sampling rate. Suppose that we transmitted a signal $m(t)$ then at receiver side, we received the continuous signal $x(t)$, which is time varying and sampled with a ...
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73 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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165 views

How can I show DTFT result in MATLAB? [closed]

I wanna show DTFT result and convolution result in f-domain are same. Additionally, I wanna show sampled function and inverse fourier transform result are same too. How can I show this? If I use ...
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1answer
84 views

About phase unwrapping

I am not too familiar with phase-related problems so I need some suggestions or corrections in a problem that might be an old but easy one. Here is my problem: given a complex signal: $$y(t) = e^{j\...
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31 views

How to calculate FFT when many samples are observed?

I was given a classwork(which I flunked) where a continuous time wave of the format below was given: $x(t) = A\sin(\omega_1 t) + A\sin(\omega_2 t)$. with different frequencies for $\omega_1$ and $\...
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64 views

Understanding the conditions for recovering a discrete time signal through sampling

So, we had a very brief introduction to the Nyquist-Shannon sampling theorem (the discrete time version). While discussing this, we have seen that multiplying a discrete time signal $x[n]$ by an ...
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34 views

Numerical error while implementing a periodic pulse signal

I'm trying to illustrate the principle of constructing a periodic signal using an elementary pattern. This is the code I use (python 2.7 + numpy + scipy.signal) : ...
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150 views

Relation between the DTFT and CTFT in sampling- sample period isn't as the impulse train period

I will quote an answer of Matt L. from this post (I didn't comment there because I can't) If you have a continuous-time signal $x(t)$, then the two signals you're talking about are $$\begin{...
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61 views

How to undo dynamic Doppler effect by software?

I have a signal affected by Doppler effect. In general, the Doppler effect changes the scale of the time and frequency domains. So, to undo this phenomenon, I am using a sampling rate converter. Two ...
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55 views

Is Oversampling a Signal Same as Discretizing the Signal?

I am confused about the new terminology 'oversampling' I have encountered very recently. To explain it better, I am going to use numerical examples. Now let's assume I am using a BPSK modulator and my ...
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79 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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134 views

frequency spectrum of a sampled signal, PSD and power discussion

Before I go into my question, I first want to review the basics of sampling a signal and at the same time I build the basics of my questions so that they make more sense. I know I have asked couple of ...
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1answer
417 views

How Does the RMS of White Noise Change with Sampling Frequency?

There is an analog system which includes the continuous-time linear equalizer (CTLE). With some .noise analysis the power-spectral density (PSD) of the noise in that system is provided. So let's not ...
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1answer
68 views

Distortion of a signal consisting of two periodic components

We have a signal $$x(t)=U_1\cos\omega_1t+U_2\cos\omega_2t$$ whose frequencies are $f_1=100\,\text{Hz}$ and $f_2=600\,\text{Hz}$. This signal is being discretisated in time using unipolar ...
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How can I find a relation between the input and output of the overall system?

I have system for filtering a continuous-time signal using a discrete-time filter where sampling is performed by multiplication with the impulse train. The frequency response of the discrete-time ...
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52 views

Finding essential bandwidth of the given function

Let the function to be $x(t) = e^{-2t}u(t)$. I want to find the essential bandwidth of the function to be the frequency at which $|X(jw)|$ drops to $1\%$ of its peak value. With a search, I found that ...
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61 views

Discretization of Sinusoidal Signals

How do I should sample two continuous sinusoids of $f_1$=1/4 Hz and $f_2$=1/2 Hz at a 1 Hz rate? Can i recover both if i bandlimit after sampling at a 1/2 Hz limit?
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Effect of sampling frequency to the center of a bandbass filter

Is it true that if you have some sort of filter, e.g. a digital bandpass filter around the frequency 1000 Hz that is given in the form of a transfer function $H(z)$ and you then change the sampling ...
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How does sampling rate of $x[n]$ relate to sampling rate in frequency domain after DFT transformation?

I've got an analog signal $x(t)$ sampled at frequency $F_s$ to obtain samples: $$ x[n] = x(t) \bigg|_{t=n/F_s} $$ I transform this signal with DFT defined as: $$X[k] = \sum_{n=0}^{N-1}x[n]e^{-i2\pi ...
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444 views

How to code a filter in MATLAB without the built-in functions?

As part of our digital signal processing course, we are asked to develop a MATLAB applet that will downsample signals for various applications. The instructor has informed us to create out own filter ...
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443 views

A voice signal is band-limited to 3.3 kHz. What is the Nyquist frequency?

I'm having a some trouble with an assignment I have to do. I don't come from electrical engineering background and would appreciate any help I can get. "A voice signal is band-limited to 3.3 kHz. ...
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Quantization of Image which have taken from partially less dark

I have picture with high resolution with 20M memory space and this image has been taken from the standing away from the window in room which has significantly less light as compared to outside. Image ...
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1answer
116 views

Uncertainty Relation between time and frequency

Typically, humans can hear sound waves in the frequency range 20 Hz to 20 kHz. If one wants to make digital record of sound such that no audible information is lost, what is the longest time interval ...
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33 views

Sampling Process Question

This is what I know about the basic sampling process I am told that fbar(t) (i.e the sampled signal) is defined for all t. I don't understand that. If n is a finite integer (..,-3, -2, -1, 0, 1...), ...
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84 views

Removing Gaussian noise and processing the remaining signal

I need to describe the process in which a given signal that has been superimposed with significant amounts of Gaussian noise. However there is a reference signal that has an accurate estimate of the ...
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50 views

Sampling and ideal reconstruction of signal

Two time discrete signals $x_1(n)$ and $x_2(n)$ are produced by sampling the continuous signal $$x_a(t) = \cos(2\pi300t) + \cos(2\pi600t) $$ with the sample frequency $F_s = 1000\ \rm Hz$. For the ...
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1answer
94 views

RF signals database

I'm trying to learn more about RF signal modulation/demodulation. I wanted to experiment with some real signals, but I don't have any data to work on. Is there any open database of RF signals? Like ...
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59 views

Synthesizing a band limited noise from time samples of white noise and the relation to sampling frequency

I wan't to synthesize a colored noise of Bandwidth of 40Mhz around some carrier (say 2.5Ghz) from samples of WGN. So, I sample in matlab using randn(1,10000) samples of normal distribution. Now, ...
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Confused on application of Anti-Aliasing Filter

I have a question about the use of anti-aliasing filters prior to sampling a finite time signal and if they actually help anything. The point of the anti-aliasing filter is to remove high-frequency ...
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148 views

AM demodulation from a real RF signal

I'm capturing an RF signal transmitted at 433.8MHz, with a bandwidth of about 50KHz. My goal is to be able to save it as a .wav file. I'm using an RTL-SDR dongle and a software named HDSDR, where I ...
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1answer
70 views

What does it mean that the DFT equals the Complex Fourier Coefficients for even frequencies?

I have a periodic signal, with period $1$ $$x(t) = \begin{cases} 1 \qquad & 0 \le t - \lfloor t \rfloor < \tfrac12 \\ 0 \qquad & \tfrac12 \le t - \lfloor t \rfloor < 1 \\ \end{cases}$$ ...
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Qrs complex detection using haar wavelet

I am using this algorithm to detect QRS complex from ECG signal that is samled at 360Hz that is decomposed to level 5 with haar wavelet In the fourth step it says that the duration of the QRS ...
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152 views

Uniform sampling of a periodic signal

According to the Nyquist sampling theorem, a sampling frequency for a periodic signal $x(t)$ with a period $T$ and bandlimited by $f_m$ Hz is given by $$ f_s > 2f_m. $$ Is it possible to relax ...