Questions tagged [downsampling]
In signal processing, downsampling (or "subsampling") is the process of reducing the sampling rate of a signal.
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What is the best method of describing the effects of downsampling on a chromatographic signal?
I am in the process of compressing a set of chromatograms to develop a preprocessing pipeline, that will end with DTW for peak alignment. During this process I have downsampled a signal from 0.4 ...
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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}) = ...
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Lowpass filter to downsample data
I have some data that is sampled at a certain rate (16384Hz). I am only interested in the 10-30Hz region, so I want to downsample the data. My idea to do this goes as follows:
I apply some kind of ...
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How does downsampling decrease the noise power?
I read one equation from a technical document, i.e., assuming the time-domain white Gaussian noise samples with variance $\sigma_{TD}^{2}$ in dB are sampled using ADC with sampling rate $f_{s}^{ADC}$, ...
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Does SDR configured with low sample rate automatically averages samples?
This is probably a basic question but I didn't find any answer online.
Suppose we configure a SDR (least say, with a maximum sample rate of 100 Msamples/s) with a low sample rate (e.g. 1 Msample/s).
...
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How to calculate phase rotation of I/Q reference samples for Bluetooth Angle of Arrival
I am trying to compensate phase rotation due to carrier frequency offset (CFO) for Bluetooth Low energy (BLE) Angle of Arrival (AoA). In BLE AoA the adv. packets carry a Constante tone extension @...
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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 ...
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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 ...
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Can we do down sampling by taking fft, omitting samples on the ends of the spectrum, and then taking inverse fft?
Suppose that we have a signal with a length of 4096 and want to down sample it by a factor of 2 and obtain a signal with a length of 2048.
Suppose that the the maximum frequency content of the signal ...
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Is this how to show decimation in the frequency domain?
Let's say I have a discrete-time signal $y[n]$ that is passed through an Ideal Lowpass Filter (impulse response $h[n]$) to get $y_1[n]$. The filter has cutoff frequencies at $\pm \pi/N$ rad.
Now this $...
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Summarization of audio in frequency domain?
I need to summarize a set of samples representing an audio to achieve a smooth zoom animation for a spectrogram in my app.
In the time domain (waveform) I achieve this by resummarizing the samples ...
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How is the DFT involved in downsampling?
I recently had my first proper class of DSP and upon completing the review of Signals and Systems my professor started working on the concepts of upsampling and downsampling. Of course as is their ...
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Effect of FIR filter on the time resolution of the signal
Let's say I have a noisy raw signal with 1GS/s sampling rate (That means the time resolution is 1 ns). Now I apply a FIR lowpass filter (window filter) of 25 MHz on it. The length of Window filter ...
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Frequency constraints on a down-sampled signal
I am preparing for an examination and am confused about one of the questions on the study guide. The question given on the study guide is given below.
We want to implement a change of sampling rate ...
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Observed Maximum Frequency Not Expected For Given Sample Rate
I'm downsampling a given .wav from 44100 to 22050 samples/second. When I play it back I'm looking at the signal with an EQ, and I would expect that I wouldn't see any content above ~11k. However, I ...
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Symmetric half band filter - redundant oversampling?
I'm making a basic symmetric decimating half band filter (M=2), with alternating 0 coefficients. The signal is oversampled by a factor of 2, at frequency $f$. I must be missing something simple, but ...
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The Effect of the Order of Downsampling and Smoothing on the Output
How do I prove or disprove:
Smoothing an image with a 3x3 filter using full convolution and then downsampling an image by 2 produces the same result as downsampling an image by 2 and then applying ...
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Moving average before downsampling: effect on Nyquist frequency?
First the simple questions:
Is there an effect on the Nyquist frequency when I apply a moving average filter on the raw data before I downsample?
And what does this do to aliased frequencies?
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Downsample (aggregate) raster by a non-integer factor, using a Gaussian filter kernel
The task is to downsample (aggregate) a raster from 100m pixel size to 460m. The aggregation should be performed using a Gaussian filter. To better understand the task, I am following the paper ‘The ...
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Why use sinc function to downsample an image in fourier domain?
I'm very confused about downsampling in image processing and the use of sinc function to do it.
I read this post [1]: 2D Fourier downsampling some time ago that talked about my own doubt, that is to ...
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Downsampling a binary file
TEXBAT is a recorded dataset about spoofing scenarios for evaluating GPS signal authentication techniques.
On this project, there are recorded GPS signals stored as complex 16- bit samples at a rate ...
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Polyphase Decimation Filter parallel inputs
I have an FPGA that's streaming in samples from a high speed ADC. The FPGA clock rate cannot run at the sample rate, so the samples are streamed in parallel (4 samples per clock cycle).
I'd like to ...
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Downsample a signal by a non-integer factor
I have a signal with a sample rate of 8.9286 MHz and I want to downsample it to 500 kHz.
Since 8.9286 is not an integer multiple of 0.5 I can't simply decimate. Which downsample techniques are ...
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Does downsampling an image twice result in a "worse" (or different) image than downsampling once
I am working on a project where the input is a large high quality image (2560 x 1440 pixels), which is eventually scaled down a lot (256 x 256) and used as input to an ML model.
For reasons that I won'...
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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 ...
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Applying 2D Sinc Interpolation for Downsampling in the Fourier Domain (DFT / FFT)
Related to The Proper Way to Do Sinc Downsampling (DFT Downsampling) for Uniformly Sampled Discrete Signals with Finite Number of Samples, how can one apply Sinc downsampling in the DFT / FFT domain ...
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question about time delay of practical filter design with sampling frequency
most system have 48khz and if i have 40tap low pass fir filter that cutoff freuqency is 300hz, filter delay is 1/48000*20 = 0.0004s
but the frequency resolution is very sparse and i think if the ...
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Downsampling an image using sinc interpolation?
I have a discrete image of size $2^N \times 2^N$ which I would like to iteratively downsample to produce a pyramid with image sizes $2^k\times 2^k, \, k=0,\ldots,N$. That is, each subsequent image ...
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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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spectrogram of a (strongly) downsampled file
I downsampled an audio file to a very low sampling rate, 48hz.
This is because I stored some information in the file, that are not really audio information but the audio format was convenient to use.
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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 ...
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How to change the samplimg rate with interpolation and decimation?
I have a wav file at a 44.1KHz. I'm trying to change the sampling frequency to 1.26MHz. For that, I need to use interpolation and decimation, and so I did, but I'm getting odd results back. It seems ...
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EEG peaks do not get identified at the correct frequencies
For my thesis I am re-analyzing a dataset where subjects were visually stimulated with 5.45, 8.57, 12 or 15 Hz. This well-known technique (steady state visual evoked potential) should elicit EEG peaks ...
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What's the correct way to align two signals downsampled at 10 Hz?
I'm trying to build a dataset where one of the features is a signal which has originally been sampled at 500 Hz, while another feature is a signal which was sampled at 100 Hz. I want to downsample ...
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Appropriate Gaussian filter parameters when resizing image
When scaling an image down it is common to first convolve the image with a Gaussian filter. Given a scale factor $0 < s < 1,$ what is an appropriate $\sigma$ to use?
For example, if $s = 0.5$ (...
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Downsampling( decimation) theory: additional frequency
I work on a simulation decimation filter: downsampling + filter.
My test environment: low data rate receiver, BPSK, square root raised cosine filter with cutoff frequency =0.5, transition bandwidth = ...
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Is there any deterministic downsampling algorithm for audio?
I was trying to use the scipy.decimate function provided in the library, but I had a question - I want a pre-processing algorithm to downsample audio in such a way ...
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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)?
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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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Image downscaling methods
I am researching downscaling methods for image downscaling. I've both read and found area-averaging to work well in Python using CV2, but the settings in MATLAB allow for it's bicubic interpolation ...
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Dynamic sampling of thermal images
My master’s dissertation subject is to analyze and implement an algorithm that would sample (store) thermal images from camera with different frequency rates to optimize database size and processing ...
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how to find the frequency of the downsampled signal?
So, I am trying to solve this question.
Consider the signal, $$x=\cos\left(\left(\dfrac{2\pi}{3} \right)n\right)$$
The signal is downsampled by a factor of two. Indicate the frequency of the resulting ...
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Does the convergence rate never increase of a Stationary Ergodic Random Processes under downsampling?
Summarize the problem
Given A Stationary Random Processes (strict sense) $X_i$ I define two Stationary Ergodic Random Processes by
$$
\bar{X}_n = \frac{1}{n} \sum_{i=0}^{n-1} X_i \ \ \text{and} \ \ \...
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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 ...
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Duration of downsampled signal in analog frequency axis
Suppose, I sampled a signal, $x(t)$ and let $x[n]$ be the sampled signal of $x(t)$. Let then I downsampled $x[n]$ by a factor of $M=3$. Let $x[n]$ after being downsampled by the factor of $M=3$ yields ...
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How to apply an anti-aliasing filter before downsampling
I have an eeg signal with two channels (f3m2 and f4m1) which is divided into epochs. I want to augment the data by taking every 5th sample. I can re-use the discarded samples to create 5 versions of ...
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What should be IQ sample rate at least?
As i read, IQ sample doesn't need nyquist criteria. What is the mathematical representation of this result? Why IQ sample doesn't need nyquist frequency? I know that can be set to nyquist frequency ...
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Increasing ADC output accuracy
Say we have a 12-bit ADC with 30 MHz sampling frequency. I want to perform several DSP operations on output digital signal so that resulting signal would have increased accuracy to 14 bits and output ...
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Is spectral density conserved after aliasing?
Will the integral of the PSD of a down-sampled signal still equal the variance in all cases
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Python: Resample without equal
I would like to resample (downsample) a signal using python in order to get an even spacing and fill gaps.
About the signal:
It consists of a vector for y (amplitude) and x (timestamps)
Very slow; $...
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