# Questions tagged [decimation]

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

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### 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 ...
98 views

### 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 ...
272 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 ...
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### How to design very narrow, sharp lowpass filters - Only DC needed?

I asked exact the same here one year ago: One year ago question I asked this question again here, because after one year, I have learned more about DSP and am thinking ways to improve it. Filter ...
72 views

### Decimating physics data

At work we run a physics simulator (video game) that operates in an inner loop at 360 Hz. Data from that inner loop is collected 60 times a second and sent out to hardware (a force feedback steering ...
3k views

### MATLAB: Decimation image

I'm trying to decimate given picture Vertically. Horizontally. Horizontally + Vertically. I know that I should use low-pass filter* and then downsample** it not to see any aliasing in image. To this ...
484 views

### Cut-off frequencies for fractional sample rate adjustment

We have a signal sampled att 22 kHz that we want to interpolate to 40 kHz. So we can do this by upsampling by a factor 20, then downsampling by a factor 11. My question regards the choice of cut-off ...
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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). ...
269 views

### Resampling: how many samples to zero-stuff or down sample?

I am a little confused about how resampling works with one filter. I get why you choose the lower nyquist cutoff when you combine both interpolation and decimation for resampling by a rational ...
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### Advantage of using FIR Polyphase Decimator over just computing FIR output every D samples

Let's say you want to implement an FIR filter $h[k]$ with $L$ taps and downsample the output: $v[k] = x[k] * h[k]$ $y[m] = v[kD]$ The "naive" way would be to compute all the samples of $v[k]$, then ...
507 views

### Optimal signal sampling reduction method : Decimation, interpolation or both?

I have a function with an equation: \begin{equation} C(t)=1.6925\left(\exp^{-0.136t}- \exp^{-1.192t} \right) u(t) \end{equation} where u(t) is a unit-step function. Then, denoting the Fourier ...
554 views

### Efficient implementation of FIR comb/decimating filter

I'm working on trying to find an efficient way to implement a FIR comb/decimating filter. For a given "prototype" low-pass filter $H(z)$, a comb that "repeats" $L$ times in the frequency domain can ...
121 views

### How are filters for polyphase decimation like?

I know in naive decimation the signal should filtered by a low-pass filter with cutoff frequency equals to Nyquist rate.I don't know how the filter banks like for polyphase decimation. Are them still ...
147 views

### 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: ...
60 views

### Decimation of motion

I have a motion signal that you can think of as a sequence of pairs (x,y); what would be the best approach to decimate this sequence at real time? I haven't found anything similar on the web and I'm ...
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### Selecting the Low Pass FIR Filter, Decimation, DSP

I'm studying DSP, but I have weakness about it. I was reading this: http://www.eetimes.com/document.asp?doc_id=1275556 But, I don't know how select the Low Pass Filter. I am assuming that this ...
205 views

### sampling a signal below nyquist rate

This question is for people working in multi rate signal processing. Using compressive sensing techniques, we can still recover a signal by sampling below nyquist rate(by decimating the signal). How ...
507 views

### up down sampling and low-pass filters

I am trying to figure out what seems very trivial thing about down sampling and up sampling. The problem that I am facing is how to find the effects of up sample on a signal followed by a filter and/...
124 views

### Filtering and decimating input as sections in multiple stages

What would be my options to decimate a large input signal available only in sections (or blocks) due to DMA type of interface? The FIR should be about order of 18 only and the total decimation factor ...
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### IIR/FIR filtering before decimation?

I am trying to design a low pass filter to apply before resampling the sensor's output at a lower rate, however I am not quite sure how to choose between the IIR and FIR fitlers. Matlab by default, ...
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### Polyphase decimation matlab [closed]

I am new to DSP, and currently trying to implement a simple polyphase decimation program in matlab. M is decimation factor, x is input (for now it is a square wave 8096 samples), y_polyDec is result ...
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### Downsampling/Decimation - When is well done?

I am working on decimation of signal, and I want to know which is the best way to understand if the downsampling is well done or not. At the moment I am comparing the FFT of the source signal and the ...
756 views

### What is the output sequence of a Decimation filter [closed]

Consider x(n) as input, y(n) as output & h(n) as filter coefficient. The filter is of 16 taps(N=16) from 0 to 15. The decimation factor of the filter is 4. When I apply x(n) to this 16 tap ...
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### CIC Filter vs Simple Downsampler

I' trying to implement a QPSK modulation/demodulation. At one point I have to decimate my signal by 4 for an easier implementation. I've read everywhere that the best way to do it is to use a CIC ...
221 views

I am using an adaptive RLS adaptive filter for noise cancellation. My sampling freq. is 500 Hz, but I am interested in only frequencies of up to 60 Hz. I filter the input and the reference signal to ...
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### Decimation of signal. How to plot frequency spectrum

I have an FDM signal from 0 to 70 MHz. The total signal contains 4 FDM signals from (0-fs/4), (fs/4-fs/2), (fs/2-3fs/4) & (3fs/4-fs). I used fvtool command in matlab to plot these signals. Then i ...
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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 ...
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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. ...