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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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Sampling and recovery using matlab

I'm trying to write a program using MATLAB that samples and recovers a given signal with different sampling frequencies The given signal is $x(t) = \sin (2\pi 200 t)$ and sampling frequencies are $...
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372 views

How does sampling rate impact Discrete-Time Kalman Filter state space modeling assumptions?

Consider a very simple, discrete-time constant position-type model for state updating in a Kalman filter: $$ x_{k+1} = x_k + w_k $$ The Kalman filter will be run with update interval $T_s$ such that ...
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214 views

Why is one of the modulated frequency spikes smaller?

This is a simple amplitude modulation experiment. Both waves are sinusoids of the type cos(2 x pi x f x t). The base signal has a frequency 100Hz, and the ...
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934 views

FFT resolution and sampling frequency

I am computing FFT of the data which I am receiving from an ADC with SPI protocol. Since resolution of FFT is related to $F_s/N$ where $N$ is the FFT length and $F_s$ is the sampling frequency of ADC, ...
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46 views

which of the analog sinusoidal frequency can not pass through the filter?

First time I am encountering this type of question so i just tried but not getting whether my logic correct or not. First let the sinusoidal signal be $X(t)=\cos(2\pi ft)$. After sampling this ...
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284 views

Am I violating Nyquist?

I am using a DAC to transmit 2 different voltage levels. High and low. At 1Gsps. There is no carrier wave or anything. These are just raw 0 and 1 time samples going across a wire. On my ADC I am ...
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98 views

Continuous wavelet transform subsampling at lower frequencies?

I am not completely confident in my understanding of wavelet theory, but since I am currently in the process of creating a CWT scalogram tool, I have to ask: Is there a theorem allowing us to ...
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876 views

Upsampling and Downsampling using IFFT and FFT

Assume in OFDM , there are N=64 subcarriers. I would like to upsample my signal by Factor 8 after IFFT and pass it through channel then downsample it by factor 8 before FFT. I can use upsample, ...
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85 views

Effect of nonlinear transformation on digital signal

Currently, I know that by passing a band-limited baseband digital signal through a nonlinear system results in the expansion of the original signal's bandwidth and creates harmonics. Therefore, I ...
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225 views

Random (Over) Sampling signal and perfect Reconstruction in Nyquist form?

Imagine we have band limited signal with bandwidth of $B$, so the required Nyquist rate would be $f_{nyq}>2B$ that is oversampled with rates $f_s$ where $f_s = M*f_{nyq}$ and $M$ is random and $M&...
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148 views

wavwrite with 32 bits per sample seems to overflow?

I am trying to generate a 32bit PCM wav file with octave, the file shall contain a single full-scale sample (0db impulse). I am getting the expected result when using 24 bits per sample: ...
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175 views

implication of sampling and reconstruction theorem

i am asking this question sorta as a surrogate for a friend at comp.dsp who posted a similar one. even though i did it for a quarter century, laying out math (using "ASCII-math") is crappy, which is ...
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86 views

What does it mean that one frequency aliases another?

So I was watching a video on sampling and the professor asked which frequencies will alias to 0 and which to $B$ if we are sampling at frequency $f_{s1}$. What does mean that two frequencies alias ...
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116 views

Denoising short, non-uniformly spaced, bandlmited sequences

Consider a bandlimited signal $x(t)$ with bandwidth $BW$. Samples of this signal are observed at non-uniformly spaced sample points in the presence of noise: $y(t_i)=x(t_i) + n_i \qquad i\in\{0,1,\...
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78 views

How to find DC bias of periodic signal from samples that include a non-integer number of periods?

I'm using an ADC to sample a periodic signal and I want to calculate the DC bias of the signal from the samples. The obvious solution is to take the average of the samples. This works fine if there ...
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549 views

Does a 20 kHz sine wave sampled at 44.1 kHz need to be reconstituted before playback?

I am interested in building a synthesizer but I am confused about the Nyquist-Shannon Theorem and sampling rates. If I sample a 20 kHz sine wave at 200 kHz and plot the data points, the plot looks ...
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49 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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77 views

What do I with the sampling period when I inverse $\mathcal Z$-transform?

Given the input $$e(kT_s) = {0.4, 0.8,1.2, - 0.9}, \quad k = 0,1,2,3$$ and transfer function $$T\left(z^{-1}\right)=\frac {z^{-1}-0.8z^{-2}}{1-1.1z^{-1}+0.3}$$ Find the output $Y(kT_s),\...
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2k views

Does Higher Sampling Rate Increase SNR?

I have AM demodulated voice samples that come from a 14bit ADC that I will filter, process, and then send to a CODEC. I can choose a sample rate of 96kSPS, 64kSPS, 48kSPS, or 32kSPS at the CODEC. ...
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503 views

Precision measurement of sine wave amplitude with ADC

I want to measure amplitude of a sine wave input precisely with a limited resolution ADC. As an example suppose that I have $1\textrm{ MHz}$ pure sine wave input to the $320\textrm{ Msps}$ $10$-bit ...
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478 views

Applying Nyquist theorem to digital vs. analog audio quality

I had a recent conversation with a friend about analog vs. digital recordings. He shared his opinion that music recorded by analog techniques is of superior sound quality to music recorded by digital ...
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58 views

Transmission of sampled signal

A signal sampled in time domain has replicas of its spectrum in frequency domain. This implies that to transmit a sampled signal we need ifinite bandwidth.How is this possible?
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523 views

DAC Sinc Roll-off vs Freq

The output of a Digital to Analog converter has a magnitude roll-off in frequency as a Sinc function with the first null at the sampling rate. Why is this the case?
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How to reconstruct/resample/interpolate a 3D signal using convolution

Assuming we have a sampled 1D signal and we want to upsample/resample, then we add 0 values inbetween the existing samples and then do convolution with a reconstruction filter e.g. $H(s) = [0.5, 1, 0....
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242 views

Variance of N samples of Noise

What is the variance of $N$ samples of white Gaussian noise? I have an Equation for a continuous time which includes an $\mathrm{SNR}$ term inside it. Now when I am going to sample it, what is the ...
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252 views

Effect of aliasing when sampling at higher rate

Considering a signal $f(t)=\sin(2\pi t)$ with frequency $10\textrm{ Hz}$: Middle and bottom plots show the results of sampling at different rates. I'm trying to understand the case shown at the ...
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61 views

Is modulation Index related to sampling rate

How does the modulation index affect a modulation scheme other than those related to main lobe's width, in case of Gaussian minimum shift keying (GMSK)? Does it affect sampling rate too?
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67 views

SD of a function of signals

Say $a_x$, $a_y$, $b_x$, $b_y$ are signals with values in $\mathbb{R}$. Say they are independednt, normally distributed variables with given SDs $\sigma_{a_x}$, $\sigma_{a_y}$, $\sigma_{b_x}$, $\...
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200 views

Interpolation formula for two dimensional signal reconstruction in the frequency domain from polar samples

In the book, Advanced Topics in Shannon Sampling and Interpolation Theory by Robert J. Marks II, one may find an interpolation formula for reconstructing a two dimensional signal from regular polar ...
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174 views

Impulse response of a continuous system sampled with zero-order hold

I've a continuous system $$F(s) = \frac{K}{Ts+1}.$$ I sample it with zero-order hold with sampling period $T_s$. The discrete system transfer function is $$ \begin{aligned} G(z) &= % \frac{z-1}{z}...
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5k views

Calculating the phase shift between two signals based on samples

I am comparing two signals in MATLAB Simulink for finding the phase between them. To do this I am inspired by using the code found here. I have two vectors of the same size which are a collection of ...
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125 views

Why sampling rate is not an option with normalized frequency in Matlab Filter Designer

My Matlab version is 2017b. When I use Filter designer with normalized frequency specifications, I cannot set the sampling rate. May you tell me why the sampling frequency cannot be specified? As I ...
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116 views

Is sampling a Fourier transformed signal and fourier transforming a sampled signal the same?

I'm having a hard time understanding an assignment that states: Draw the complex spectrum of the sampled signal $f(t)$ (periodic and continuous). Do this, by first calculating the Fourier ...
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79 views

Is it possible to do deconvolution with two data sets that have different sampling rates?

I have some terahertz spectroscopy time series data, a reference set with 2048 data points taken every 0.0521 picoseconds, and the sample data set with 544 data points taken every 0.0781 picoseconds. ...
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129 views

Octave error - STFT parameters when detecting pitch in guitar audio signals

I am working with this STFT method to detect pitch in monophonic guitar audio signals. The method is working correctly for medium pitches (above 150Hz). However, in low notes I have some issues. ...
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Bandwidth vs. sampling rate of DAC

What is the difference between the sampling rate and the bandwidth of a DAC? I have found in one paper a DAC speced as 15GHz 3dB bandwidth, and 64GS/s sampling rate, and I haven't been able to relate ...
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383 views

FFT and number of samples relations

I am new in signal processing. I generated a signal with $f_{in}=10 \mathrm{kHz}$ and also take 64 sample from this signal after doing some process in an ADC block. I want to convert the result to the ...
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53 views

How to perform sampling for the discrete data entered to IFFT in OFDM?

The relation $N= \textrm{BW} /\Delta f$, where $N$ is number of subcarriers, $\textrm{BW}$ is the available bandwidth and $\Delta f$ is the subcarrier spacing (subcarrier bandwidth) is reasonable for ...
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384 views

What are two different continuous-time signals when sampled at $10\textrm{ Hz}$ would produce the sequence $x(n)=\cos(n\pi/8)$?

The answer is: $\cos(1250\pi t)$ and $\cos(21250\pi t)$ I’m not able to verify. My understanding is that when you periodically increase $t$ by $1/10$ ($10$ here is the frequency, so $1/10$ is ...
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2k views

Correlation of two signals at different sample rate

I have a signal $X$ and I want to find signal $Y$ in $X$, I can achieve this by cross-correlation. Signal $X$ is sampled at $8000\textrm{ Hz}$, and $Y$ signal is sampled at $44100\textrm{ Hz}$. My ...
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79 views

Representing a positive 0-limiting continuous time domain function, in terms of spectral samples, outside of a window

Bit of an odd question Assume you have a known function $x(t)$ which is continuous, but approaches but is not equal to, 0, on the interval $[-\infty,\infty]$ . You know also that it approaches 0 ...
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531 views

frequency domain zero padding in OFDM

I have a matlab code for OFDM system, in this code the auther added a zero padded subcarriers before the IFFT stage, in the middle of the raws, and added zero padded guard interval after IFFT, my ...
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118 views

What is advantage of Logarithmic Sampling?

Logarithmic Fourier Transformation This paper starts off in the abstract saying that the given audio signal is sampled logarithmically. We also know that the human ear has a sort of a filter bank ...
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121 views

Logarithmic Spacing

What is the meaning of sampling logarithmically? How do you space the samples logarithmically? Or to rephrase the second question, How to sample an audio signal logarithmically? It would be ...
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816 views

Why is aliasing inherently non-linear?

E.g. when having 2 signals $x(t)$ and $y(t)$ and transforming each one with adding their spectra, the operation is linear, as the result would be the same as the transformation of $(x + y)(t)$. Even ...
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5k views

Exponential moving average cut-off frequency

I am trying to implement low pass filter from this example. What is the cut-off frequency for this type of filter? Is it $F_s \frac{1-\alpha}{2\pi\alpha}$, where $F_s$ is sampling frequency?
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1k views

Laplace transform of product of signal and impulse train

I'm reading 'Discrete Time Control Systems' book by Ogata and came across a few statements (specifically, (3-1) and (3-2)) which I have not been able to understand. It is said that any continuous ...
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231 views

Uniform sample rate

I have some sensors connected to an Arduino Due. The Arduino sends the buffer of data over the its SerialUSB connection. The last element of this buffer defines when are passed 1 seconds (it is 0 "...
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576 views

Sampling rate vs ADC noise tradeoff

I have a digital sensor that can output at two frequencies (250Hz, 1000Hz), but with different RMS AWGN noise (.35 units RMS, .5 units RMS respectively). The signal of interest has a single frequency ...
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106 views

Which window function to use for QPSK signal?

I am trying to Receive a QPSK signal and for Sampling I need to recover clock. Now QPSK Signal is generated at 2.4GBaud. It is than sampled at 80GHz.Than further it is downsampled to 10GS/s (Symbols ...