Questions tagged [upsampling]

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Up-sampling images and the Periodicity of the copies

In the three figures below, $H(e^{j\omega})$, $H(e^{2j\omega})$, and $H(e^{4j\omega})$ are shown. I understand that up-sampling shrinks the spectrum. However, I need a few clarifications: Why does up-...
mmcmp's user avatar
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2 answers
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Upsampling of a signal

A low-passed signal, bandwidth limited to 4KHz is originally sampled 10 KHz. If I want to resample it at 20 KHz, I take these steps. Are these correct? Am I missing an step? First we need to filter ...
Jacob's user avatar
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2 answers
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upsample impulse response

I have a system and I know its impulse response $h$, this impulse response was recorded at $f_s = 48000 \texttt{Hz}$, now I can use Matlab to get the system output to an arbitrary signal ($x$) by ...
user2982010's user avatar
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Is this proof valid?

Consider a discrete-time sequence, $y[n]$, defined as: $$y[n] = \frac 12 x[n] + \frac 12 (-1)^n\: x[n]$$ where $x[n]$ is another discrete-time sequence. The DTFT of $y[n]$ defined as $Y(e^{j\omega}) = ...
Ahsan Yousaf's user avatar
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Correct OFDM oversampling method

I need to oversample my OFDM signal, however I have issues understanding which OFDM oversampling method is the recommended one. First method : Before taking the IFFT, the OFDM subcarriers are padded ...
Nicolate's user avatar
2 votes
2 answers
122 views

Is downsampling LTI for bandlimited inputs?

This question stems from the discussion we had on a previous question of mine. The point of contention is whether the downsampling operator is time invariant or not. Which gives us a new condition to ...
Ahsan Yousaf's user avatar
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Is the following system LTI and what is its purpose?

Above is a block diagram of a discrete-time system $T\{x[n]\} = y[n]$. Here, $h[n]$ is the impulse response of an arbitrary LTI system. Firstly, is this overall system LTI? I don't think so because ...
Ahsan Yousaf's user avatar
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Pre- or post-filtering for image doubling

I am doubling the resolution of images by bilinear resampling (which amounts to averaging). I seem to understand that this should be combined to a sharpening filter for better quality of the ...
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6 votes
4 answers
1k views

Is adding a mean point between every two points a valid way of upsampling?

Suppose we need to double the sampling rate of an audio signal. Is adding a mean point between every two points a valid way of upsampling? If no, then why not? For example, in images, pixels may be ...
Ritesh Singh's user avatar
2 votes
2 answers
97 views

Upsampled signal values

My question is: after upsampling a signal, does the output signal contain the original signal values? The diagrams I saw so far (on wikipedia and different forums) have always shown the original ...
Zsolt's user avatar
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Does the combined pointsample+bilinear upscaling algorithm have a name?

I have been performing digital image upscaling of pixel art in one of my hobby projects, and the two simplest upscaling algorithms are point sampling or bilinear upscaling. Point sampling exhibits ...
trojj's user avatar
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1 answer
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Zero padding versus zero stuffing

Let's say I want to increase the sampling rate of my signal, $f_t$, from a sampling frequency $f_s$ to some multiple $Mf_s$. One way to do this is to add zeros between the samples of $f_t$. This ...
In the blind's user avatar
1 vote
1 answer
225 views

How to upscale an image using a Gaussian filter in R?

I want to resample a raster from 15m to 460m using a Gaussian filter. The goal I am having a coarse image which I want to downscale. I also have a fine resolution band to assist the downscaling. The ...
Nikos's user avatar
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2 answers
451 views

Quadrature Detector with a single ADC

I have a quadrature detector, which provides I and Q baseband signals with 4 kHz bandwidth, set by detector's LPF. I digitiize them on two ADCs with sampling frequency 48 kHz, make Hilbert ...
K-man's user avatar
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1 answer
271 views

How to choose correctly oversampling ratio?

As many of us have noticed, last two months I am working on GMSK modulation and demodulation design. Before continuing my research, I want to be sure I chose the correct oversampling ratio ( how many ...
FrimHart64's user avatar
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1 answer
198 views

How to maintain DFT symmetry for zero padding in frequency domain? [duplicate]

I am looking for a mathematically correct way of zero-padding in the frequency domain when we have an even number of points. (i) If we zero pad in the center of the DFT, after the Nyquist value, the ...
AChem's user avatar
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1 vote
0 answers
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Upsampling a non equally spaced signal [duplicate]

I have a signal that has not an equally spaced sampling time $T_s$, and I would like to upsample it with an equally spaced $T'_s$. My first approach was to interpolate it with a spline and then obtain ...
DKL's user avatar
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1 vote
1 answer
238 views

Why does upsampling and interpolation by convolution introduce a shift compared to imresize?

For purposes of understanding the process - not for any practical purpose for which I could use imresize - I wanted to show that 2x upsampling followed by convolution with an appropriate kernel (...
SheppLogan's user avatar
0 votes
1 answer
88 views

reconstruct the low resolution signal before upsampling

When we upsampling a discrete 1d signal by 2x, we first interleave the signal by 0 and add zero padding, then pass through a low pass filter. low resolution signal [x1, x2, x3, x4] -> interleave 0 ...
Zongze Wu's user avatar
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1 answer
518 views

Applying 2D Sinc Interpolation for Upsampling in the Fourier Domain (DFT / FFT)

Related to The Proper Way to Do Sinc Upsampling (DFT Upsampling) for Uniformly Sampled Discrete Signals with Finite Number of Samples, how can one apply Sinc upsampling in the DFT / FFT domain for a ...
Eric Johnson's user avatar
-1 votes
1 answer
277 views

Change Amplitude Magnitude after Interpolation Algorithm

I try to implement interpolation algorithm. I code this using MATLAB. Firstly, I create a signal and I upsample my signal using zero padding. ...
bb0667's user avatar
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2 votes
1 answer
697 views

The Proper Way to Do Sinc Upsampling (DFT Upsampling) for Uniformly Sampled Discrete Signals with Finite Number of Samples

Given a signal $ \left\{ x [ 0 ], x [ 1 ], ..., x [ N - 1 ] \right\} $ what would be the correct way to upsample it in the frequency domain (Sinc interpolation)? Note: Added as a request by the answer ...
David's user avatar
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3 votes
1 answer
1k views

Synchronizing 2 time series signals at slightly different sampling frequencies

I'm working with an embedded system that has two acquisition channels and unfortunately, their clock crystals are slightly out of sync. Even though both boards are configured by software to sample at ...
Amudsen's user avatar
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2 votes
1 answer
204 views

Efficient Implementation of Digital Upconversion

I have an application where I have a pulse shaped QAM signal, at 2 samples per symbol. I need to take the I/Q samples and perform quadrature upconversion so that they can be output on a DAC that's ...
user67081's user avatar
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2 answers
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when is downsampling followed by upsampling shift invariant

i have a set of images that i need to send through an hourglass-type convolutional system. I understand convolutions are shift-invariant, so i will ignore them the question is then: If I downsample a ...
Anatoly's user avatar
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0 votes
1 answer
327 views

Resampling a Zero Order Hold signal

I have a sine signal whose frequency is $f$ sampled and then reproduced by a DAC as a zero order hold signal with sampling period $T_1$. The DAC signal is then reacquired with a sampling period $T_2 = ...
Hybridslinky's user avatar
1 vote
0 answers
50 views

3D interpolation of a volume with irregular upsampling

Given a collection of 2D slices which as a whole corresponds to a 3D volume (medical image of an organ), I only take specific slices (i.e. I replace the ones I dont want with zeros) and so, I end up ...
SheppLogan's user avatar
0 votes
1 answer
220 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 ...
dereks's user avatar
  • 101
2 votes
1 answer
270 views

AWGN noise variance in upsampled BPSK signal

When I simulate BER for basic PSK schemes, I set the IQ complex noise variance to $\sigma^{2} = \frac{E_{s}}{2*R_{m}*R_{c}}*\left( \frac{Eb}{No}\right)^{-1}$ where $E_{s}$ = Energy per modulated ...
Moses Browne Mwakyanjala's user avatar
1 vote
2 answers
270 views

Should upsampling impact the amplitude of an autocorrelated signal?

I want to autocorrelate a signal using numpy's correlate method. Let us consider a 10 minutes long signal sampled at 2,000SPS: ...
Sheldon's user avatar
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3 votes
2 answers
316 views

Getting error while performing upsampling of an audio signal processing using low pass filter in python

I want to perform upsampling of an audio signal introducing zeros between samples to create a longer signal with factor of N=2. The sampling rate is 44100Hz, time = 5sec. ...
user57898's user avatar
0 votes
1 answer
384 views

How does upsampling/interpolation/oversampling help with noise shaping?

That's all, Why does upsampling improve the resolution and signal-to-noise ratio? What makes it so good for noise-shaping
Nyquist-er's user avatar
2 votes
1 answer
349 views

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, ...
agile's user avatar
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0 answers
48 views

In repeated upsampleing and downsampling by 2, how do i calculate the output Y(z)?

For example, if X(z) -> {downsampled by 2} -> {upsampled by 2} -> Y(z) Given that: X(z) = 1+z^2+z^12+z^19 How do I compute the value of Y(z)?
roman numerals's user avatar
0 votes
1 answer
89 views

How is non-integer upres downres (1080p game on a 1440p screen etc) calculated

Please redirect me if this is not the right place to ask. I was unable to find a straightforward answer to this question. What I am wondering is, if I am playing a 1080p game on a 1440p display, what ...
Gappy Hilmore's user avatar
1 vote
1 answer
4k views

How to correctly use sinc interpolation in Matlab?

What is the right way to use sinc interpolation for a given discrete signal $x[n]$? Following is the sinc interpolation formula: $$x(t) = \sum_{n=-\infty}^\infty x[n] \mathrm{sinc}\left(\frac{t-nT}{T}\...
level2fast's user avatar
0 votes
1 answer
159 views

Perfect reconstruction in two-channel filter bank

[from Discrete-time Signal Processing by Oppenheim and Schafer, 3rd ed.] I was not able to prove this: If the analysis and synthesis filters are ideal so that they exactly split the band 0 ≤ |ω| ≤ π ...
DSPinfinity's user avatar
1 vote
2 answers
168 views

Book suggestion for upsampling and downsampling

I want to ask for a good textbook or online material which explains in detail: -the time and frequency domain mathematics behind upsampling and downsampling. -easy to follow Note: Oppenheim's ...
DSPinfinity's user avatar
8 votes
5 answers
6k views

How can I upsample 22 kHz speech audio recording to 44 kHz, maybe using AI?

I have a 22 kHz mono audio recording, which is mainly speech, a reading. I would like to upsample somehow to 44 kHz, to improve the audible quality. I have read about there are AI methods for ...
Konstantin's user avatar
0 votes
1 answer
421 views

How to calculate the upsampling rate (sample per symbol) for a recorded raw IQ .wav file?

I am not familiar with raw IQ wave files. For tetra-1 signal, the bit rate is $36$ k bps (or $18$ k as the symbol rate). If the Fs saved in the .wav file is $48000$ Hz, what should be the SPS (sample ...
Linda's user avatar
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0 answers
160 views

Cosine modulated impulse response

How do we show $y_0(n) = y_1(n)$ when $h_k[n] = h[n] \cos(\frac{2\pi}{L} k n )$
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Why does upsampling in the frequency domain produces replicas of the signal in spatial/time domain [duplicate]

The experiment is the following: Given a 1d signal, e.g., a vector of values $f$. Let $F$ be its DFT, i.e., $F=fftshift(fft(f))$, shift is just to have DC centered. Then we upsample $F$ as $uF=...
SheppLogan's user avatar