Signal Processing Stack Exchange
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Questions tagged [decimation]

Decimation is a technique for reducing the number of samples in a discrete-time signal.

Decimation is a two-step process:

  1. Low-pass anti-aliasing filter
  2. Downsampling

An example of decimation: the frequency of a recorded sound can be raised an octave (in other words, doubled in frequency) by eliminating every other sample without changing the sampling rate. This will result in aliasing if the sound contains overtones whose (doubled) frequency will exceed half the sampling rate. Decimation aliasing can be avoided by eliminating those overtones with a lowpass filter before downsampling.

Source: Wikipedia

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Downsampling a signal with decimate

I'm experimenting with decimating a signal, in this case a unit impulse. I'm using Python, with pylab. First, I create a unit impulse, and decimate it by 5. x = r_[zeros(0), 1, zeros(100)] N = 2 ** 14 q = 5 y = decimate(x, q,…
Lance
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Decimation filter that throws away every $N$th sample, keeping multiple samples: is it valid?

While working on an existing project, I came across a piece of code that does a decimation filter in a way that I find not obvious. In this code, every 6th sample is being thrown away. The result is being fed to FFT functions, in order to calculate…
ZenJ
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What is the point of decimation?

The following makes sense to me: Decimation reduces the number of samples so it reduces the amount of data that is metered across networks and reduces the processing time for chips. That sounds great. However, the following does not make sense to…
Nick Lang
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Decimating a discrete time cosine function

Let $x[n] = \cos(wn)\ \ $ be our signal. Let the other signal be $x_2[n] = \cos(2wn)\ \ $ . The spectrum of $x[n]$ and $x_2[n]$ are well defined and consist of impulses at the relevant frequencies with weight $\pi$. However, if we interpret $x_2[n]$…
Dost
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How much to decimate?

What I don't understand is the connection between the sample rate, the baud rate, decimation and using convolution or correlation. I'm sampling at 2048000 Hz but I don't know my baud rate, I estimated it (by looking at the time length of one of the…
Nick Lang
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Decimating Long Data in Chunks

I have a very long data up to 8 millions of samples and want to decimate it to order of 1000s. I'm using following Matlab code to do this: f = numberOfSamples/N; %N is number of points after decimation p = factor(f); % temp = rawData; %with length…
Aenid
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How does decimation work without losing samples?

For example, changing the frequency from 32.768Mhz to 2kHz there is a scale down of 16384. From the algorithms I've seen you have to discard 16384-1 samples and only count the 16384th sample. However, that many samples being lost will lose important…
kepsek
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Decimate signal by 64

I have a 16bit SAR ADC sampling at 6.4kHz. The Anti-Aliasing Filter is a active 4th order Bessel lowpass (2x LTC6081) with -3dB at 200Hz and -80dB at 3.2kHz. Now I want to decimate these 6.4kHz to 100Hz. The uC is a 8bit RISC (Atmel AVR) running at…
Andy
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Choosing the right decimation number

I am a hamradio hobbyist with little knowledge in SP. I have to decimate the sampling rate of the received FM signal so I can get to the sampling rate that is supported by the sound card of my computer. In the manual it says that I can choose the…
Jack
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Disadvantage of high downsampling rates with CIC filters

For a lock-in amplifier I am downsampling the demodulated baseband signal prior to the final low pass filtering. This lock-in amplifier is implemented on an FPGA (myRIO of National Instruments). Therefore I use CIC filters. I've reading a lot in…
Slev1n
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Questions on Need of filtering before decimation?

This is a question related to the need for filtering before decimation. I understand that there are many questions likewise in this forum. I have gone through these and still little confused (or) may be overthinking about it. I have a test…
Jani
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ADC Resolution after oversampling

I am using an ADC (ltc2378) with a resolution of 20 bits. Based on the datasheet this resolution corresponds to an LSB calculated by the equation ($2 V_{\text{ref}}/2^{20}$), i.e., 9.536 µV. In order to achieve a better resolution of 24 bits as…
MrT
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