Questions tagged [decimation]

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

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70 views

Is the decimation process time invariant?

I'm stuck at exercise 1.18 in Understanding Digital Signal Processing by Richard G. Lyons: There is an often-used process in DSP called decimation, and in that process we retain some samples of an $...
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1answer
27 views

Coherent averaging of polyphase components of a signal

I want to subsample a multi-band signal to introduce controlled aliasing. My frequency components are uniformly distributed across the spectrum (comb structure) and occupy a relatively narrow ...
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31 views

Python resampling and filtering question

Intro Hi I'm looking for someone with some experience to walk me through some questions I have regarding resampling (downsampling) in Python. Here is my problem: I have accelerometer data that comes ...
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2answers
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Downsample: resample vs antialias fitlering + decimation

I have a discrete signal sampled @Fs. I need to downsample it to Fs/k. Main reason is to reduce signal bandwidth and speed up computation : I'm only interested in a reduced bandwidth < Fs/2k. Some ...
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21 views

resample interpolation decimation filters algorithm

I'm creating a program in order to perform Resample, Interpolation and Decimation Frequency. ...
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1answer
476 views

Decimation and filtering in the frequency domain

I'm working on a Software Defined Radio project where I'd like to low-pass filter and decimate an analytical signal (IQ) sampled at 96ksps. Let's say the low-pass filter has a cutoff at 5kHz and I'd ...
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RSP1A sample rate vs if bandwidth

I'm using the RSP1A SDR and I want to understand how to choose the best configuration for receiving a signal of 125 khz bandwidth. I would like to know if when choosing the option 200 KHz IF ...
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2k views

Understanding audio downsampling code (JavaScript) and adapting to a different ratio

I inherited responsibility for some audio downsampling code that I don't fully understand: ...
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1k views

Difference between Sub Sampling and Down Scaling of Images

I know that there are many ways to upscale (interpolate) an image using bilinear, bicubic, sinc... Somehow, these same algorithms can also be used to downscale an image. But when it comes to ...
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3answers
654 views

Image Pyramid Without Decimation

I have an image processing algorithm which uses Gaussian and Laplacian Pyramid Decomposition. At each level of the pyramid the algorithm decimates the previous level by a factor of 2. The LPF the ...
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43 views

Moving noise floor spectrum after decimation

Currently I am working in a spectrometer with a stage of decimation previous the fft. In particular I am decimating with a factor of 16 in two stages of 4 each one. I attach a diagram of the model (I'...
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1answer
34 views

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 ...
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Filter design for decimation of 1.1 kHz sensor sample rate to 100 Hz processing rate

Suppose, you have a signal source which is sampled by 1100 Hz and is "somehow" band limited to either 235 or 440 Hz. In my application, that's the ST IIS3DHHC accelerometer. There is an appnote for ...
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120 views

Decimation vs Mean in downsampling operation

Let's suppose I have a discrete signal $x[n]$ with a certain frequency $f_x$. Now, due to various unimportant reason, I want to obtain a new signal $y[m]$ with a new frequency $f_y = \frac{f_x}{k}$, ...
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2answers
5k views

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....
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4answers
366 views

What's the advantage/disadvantage of oversampling followed by decimation, verses sampling at the correct rate to begin with?

I read somewhere that oversampling somehow reduces sampling noise? How to quantify the reduction in noise? and why would it reduce noise if you are decimating the oversampled signal. What's the ...
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Effect of down mixing on complex demodulation method

As I know, IQ demodulation (complex demodulation) consists of three steps: Down mixing X(complex demodulation)(t)=X(real signal)(t).{exp⁡[(-i2π(f_demodulation).t)]} low pass filtering decimation ...
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Breaking down a higher order filter to simple cascade of averages

I am having the following filter structure, which is a second-order decimation: Which actually implements the following equation/code: (ans-0.2727) $$\frac{2}{N(N+1)}\sum_{i=1}^{N} (N+1-i).d(i)$$ <...
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How to move a linear block before an Integrator block?

I have the following discrete time blocks which acts as a decimation filter. My objective is to linearize the piecewise linear outputs using $O$ and $G$; the purpose of these two variables is ...
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Proper way to implement a decimation

I have an input signal with bandwidth 2.5 MHz. Let's say it's filtered using analog Butterworth low-pass filter. I would like to sample the signal using AD9203 10-bit 40 Msps ADC. If I understand ...
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3answers
572 views

Upsample / Downsample a Signal from 1920.93Hz to 1920Hz [duplicate]

I've just learned that the A/D converter I am using is not sampling at my desired sampling rate. I request 20 seconds of data at 1920Hz and I receive 38400 points of data that were actually sampled ...
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167 views

Decimation Aliasing

Lets say you have a signal which is sampled at rate $f_s$ and the bandwidth after sampling is $B$. Now you want to decimate this signal with a new sample rate $f_{s, new}$ where $f_{s, new} < f_s$ ...
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1answer
306 views

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 ...
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1answer
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Does lowpass filtering and decimating improve SNR?

I did not manage to find clear answers to this question: does decimation after an appropriate lowpass filter improve the signal to noise ratio? To investigate this question, I considered data ...
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5answers
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How to design very narrow band, very sharp low pass filters - Only DC needed?

I am using a DSP processor to sample signals at 108kHz and I only want to get the DC part out of it. Such a high sampling rate is used because I want to use oversampling to reduce quantization noises. ...
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187 views

Differences between Matlab resample() and CMSIS decimate_f32()

I am pretty new to DSP and I need some help to pinpoint my mistake. I am using Matlab to simulate an embedded environment. I have three signals all centered on 50Hz (6.4KHz sampling rate) which have ...
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1answer
436 views

Sample Rate Conversion between 32K and 44.1K

I would like to know what are possible/typical efficient implementations (preferably in fixed-point DSP) of synchronous sample rate conversion between 32KHz and 44.1KHz (audio applications). Also, I'd ...
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2answers
1k views

FIR-Decimation and Low-pass filter (taps vs number of input points vs number of decimation stages)

I am new to digital filters and trying to understand parameters behind them. Scenario I am trying to get DC value from signals sampled at 100kHz sampling rate. such high frequency is used due to ...
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133 views

Interpolated FIR (IFIR) for decimation

I'm interested in implementing an optimized 5x decimation stage. However it seems the resources needed are significantly more than 4x or 8x composed of cascaded 2x stages. For general purpose FIR ...
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2answers
345 views

Interpolation and decimation

I have a sinusoid in continuous time, with a frequency of 18kHz, it is sampled ideally with a continuous to discrete convertor, with a frequency of 27kHz. After that, we change the sampling speed in ...
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1answer
306 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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5answers
8k views

Output gain when upsampling and downsampling

Do the processes of upsampling and downsampling affect the magnitude of the transform of a signal? And if not, why am I seeing everywhere that a filter with gain different from 1 is applied after up/...
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1answer
584 views

Filtering vs. decimation

I have a signal collected via an RTL-SDR at 2.4Msps. I want to narrow in on a small signal within this (an FM broadcast station, for example). I am multiplying my signal by a complex exponential to ...
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Walking through a spectrum a little at a time

I am capturing samples with an RTL-SDR: ...
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1answer
741 views

Resampling time series to regular array, then downsampling (Butterworth)

Long time reader, first time poster. I have a few very simple questions that are troubling me and I am hoping that one of you guys can help me out. Setup & Aim: I have a time series that I want ...
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1answer
3k views

Python's $\tt resample$ vs $\tt resample\_poly$ vs $\tt decimate$

I have multiple signals each measured with a sampling rate 300Hz. They are mostly periodic, although there are some parts of some of the signals, that seem to be random and do not follow the rest of ...
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2answers
84 views

Besides computational costs, is filtering, decimating, then filtering different from just filtering?

Background: I have a variety of BPSK which uses a raised cosine transmitted pulse shape: $$ h(t) = {1 \over 2}\, (1+\cos(\pi t))\, \Pi(t/2) $$ After matched filtering in the receiver, the end result ...
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4answers
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Basic method for 2x oversampling?

I would like to know if the following method of 2x oversampling is correct: Interpolate: Take an original signal sampled at 44100Hz as input Upsample by adding a zero after each original sample to ...
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1answer
1k views

Downsampling: Mathematical derivation

The problem I am having is related to sample rate conversion and more precise to sample rate reduction. I have been working on the paper Interpolation and Decimation of Digital Signals Tutorial Review ...
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1answer
340 views

Is FIR decimation the fastest possible method for integer downsampling?

For a digital music synthesizer I am developing, I have a stream of incoming samples $x_i$ and would like to downsample by $M$ to obtain a stream of samples $y_{Mi}$. I am currently bandpassing the ...
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1answer
446 views

Fequency Domain Oversampling - decimating when going back to time domain

I'm currently trying to simulate Frequency Domain Equalization, and the effect that over sampling in the frequency domain has on the affect of the equalization. If I understand things correctly this ...
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1answer
153 views

Amplitude loss during resampling with IIR

I have a problem in that I am resampling a signal and loosing amplitude. The steps I do are the following, in c++: Upsample/interpolate signal by 16x by padding with zeros. Run an IIR Bessel 2nd ...
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1answer
307 views

Reordering frequency translation and decimation

I'm trying to understand the behavior of two different methods of decimating and frequency translating a signal. At this point, I'm only swapping the translation and decimation; I'm not doing any ...
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1answer
907 views

Timing syncronisation using polyphase decimation filter

This question is regarding application of polyphase decimation filter in symbol time correction. How does choosing a perticular "polyphase branch" in a polyphase decimation filter result in timing ...
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1answer
3k views

Can you decimate / downsample a signal in frequency domain just like you can interpolate / upsample it?

To interpolate a signal I can just zero pad it in the frequency domain. If I want to decimate the signal, can I just discard some part of the frequency domain? So in MATLAB this works: ...
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1answer
748 views

scipy.signal.decimate vs array operations

The following program generates a signal with a bit of noise according to some bits. I then try to decode the signal using convolve and decimate. 2 problems I notice: The whole this gets thrown out ...
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1answer
348 views

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 ...
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1answer
2k views

Upsampling/Interpolation and Downsampling/Decimation

I am having trouble figuring out exactly what is happening the process of downsampling/upsampling and the output in the example given below: So the 100Hz sine wave is sampled at 2000Hz resulting in a ...
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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 ...
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265 views

Symbol timing recovery algorithms

I am trying to implement the symbol timing recovery loop and for that I have chosen two algorithm to compare my results one is feedforward and Gardner TED. One thing that is confusing me is smoothing ...