# Questions tagged [decimation]

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

71 questions
Filter by
Sorted by
Tagged with
24 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'...
28 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 ...
19 views

### 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 ...
27 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 $f_y = \frac{f_x}{k}$, ...
84 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 ...
24 views

### 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 ...
34 views

### 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) $$\frac{2}{N(N+1)}\sum_{i=1}^{N} (N+1-i).d(i)$$ <...
23 views

### 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 ...
33 views

### 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 ...
130 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 $f_{s, new} < f_s$ ...
237 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 ...
144 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 ...
120 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 ...
371 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 ...
245 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 ...
411 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 ...
30 views

### Walking through a spectrum a little at a time

I am capturing samples with an RTL-SDR: ...
301 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 ...
315 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 ...
2k 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 ...
75 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 ...
892 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 ...
271 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 ...
644 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 ...
329 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 ...
133 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 ...
1k 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: ...
279 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 ...
2k 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: ...
584 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 ...
293 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 ...
2k views

### 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 ...
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 ...
64 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 ...
1k views

### 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 ...
4k 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....
65 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 ...
7k 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/...
371 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 ...
891 views

### 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). ...
191 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 ...
2k views

### 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 ...
1k views

### 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 ...
467 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 ...
491 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 ...
114 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 ...
120 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: ...
3k views

### 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. ...