## Decimation in Frequency FFT

Started by in comp.dsp13 years ago 4 replies

Hi, I am implementing a Decimation in frequency algo using MATLAB. Can anbody give an efficient way of passing the twiddle factors to a...

Hi, I am implementing a Decimation in frequency algo using MATLAB. Can anbody give an efficient way of passing the twiddle factors to a 2 input 2 output butterfly. Thanks, Praveen

## Question for bit number decision of decimation filter's output

Started by in comp.dsp10 years ago

Hi All, I'm a HW engineer and need to design decimation filter for sigma-delta ADC. After reading some articles and discussion from internet, I...

Hi All, I'm a HW engineer and need to design decimation filter for sigma-delta ADC. After reading some articles and discussion from internet, I knew decimation filter has 2 major function, downsample and 1-bit to multi-bit data conversion. As all replies for http://www.dsprelated.com/showmessage/2836/1.php, the output bit number seems the max value of 1s accumulation, ex. 12-bit for 4095 oversa...

## using IIR or FIR to implement the lowpass filter for downsampling?

Started by in comp.dsp7 years ago 12 replies

For downsampling (decimation) one normally uses low pass filter before downsampling (anti-aliasing filter). I have thought that FIR is the...

For downsampling (decimation) one normally uses low pass filter before downsampling (anti-aliasing filter). I have thought that FIR is the best choice here for the low pass filter implementation for this case. But I was reading this page: http://www.dspguru.com/dsp/faqs/multirate/decimation and it said in 2.3.1 under "How do I implement decimation?" "To implement the filtering part...

## Dumb Decimation Technique?

Started by in comp.dsp11 years ago 20 replies

DSP gurus: Concerning decimation by a rational scale factor, L/M, where L = upsampling factor, M = downsampling factor, M > L (hence,...

DSP gurus: Concerning decimation by a rational scale factor, L/M, where L = upsampling factor, M = downsampling factor, M > L (hence, decimation occurs) Define Decimator A as Input -> FIR bandlimit(L pi / M) -> Two-point interpolation -> Output Define Decimator B as Input -> Upsample by L -> FIR bandlimit(pi / M) -> Downsample by M -> Output In DecA, the two-point interpol

## fir decimation filters

Started by in comp.dsp13 years ago 7 replies

hi.. I wnat to design a fir decimation filter with 32 taps , input width 16, coefff width 16 .plz give me suggestions to implement this.

hi.. I wnat to design a fir decimation filter with 32 taps , input width 16, coefff width 16 .plz give me suggestions to implement this.

## how to caculate the ripple of sigma-delta conveter

Started by in comp.dsp13 years ago 3 replies

Hello, Let's consider a Sigma-Delta analog to digital converter following by decimation filters. Do the passband ripples of the...

Hello, Let's consider a Sigma-Delta analog to digital converter following by decimation filters. Do the passband ripples of the decimation filter play a significant role in not to degrade the precision afforded by the Sigma Delta ? I have been said that if a Sigma Delta converter hold a precision of n bits, the passband ripple of the folowing decimation filter must be inferior t...

## Decimation vs. Collapsing and their spectral effects

Started by in comp.dsp14 years ago 23 replies

Hello all, I am struggling with what happens to the time axis in a sampled sequence when it is collapsed by adding every two samples...

Hello all, I am struggling with what happens to the time axis in a sampled sequence when it is collapsed by adding every two samples together, with or wihout averaging. I am working in the spatial domain but believe the principles should be the same as with time varying signals. I understand decimation and how it effectively resamples at a lower sampling frequency and has the potential ...

## Decimation/interpolation

Started by in comp.dsp15 years ago 17 replies

Hi, I have a, maybe stupid, question about decimation and interpolation. Let's say we have a signal sampled at 20KHz, so with an...

Hi, I have a, maybe stupid, question about decimation and interpolation. Let's say we have a signal sampled at 20KHz, so with an useful bandwidth of 10KHz. This is ideally low passed at 5KHz, then is downsampled (decimated) by a factor two. This means taking one sample and discarding the next, or, in other words, taking all the even samples, or the odd ones... Now, in theory taking...

## decimation and resolution

Started by in comp.dsp4 years ago 11 replies

Hi everyone, I have an encoder which is delivering 22bit data for a 360 rotation. The rotation is accomplished in ~800ms but the serial link...

Hi everyone, I have an encoder which is delivering 22bit data for a 360 rotation. The rotation is accomplished in ~800ms but the serial link from the encoder is running such that we will sample values at 25KHz (that is a requirement). It roughly means we are grossly undersampling the amount of information the enconder is capable to provide. Would this 'decimation' have an impact o...

## How to implement an efficient ALL-PASS decimation?

Started by in comp.dsp11 years ago 3 replies

Hi all: I want to implement a Decimation with D=6 to decimate from 5Mhz to 833Khz, but all the 833Khz content is with interest, so the priori...

Hi all: I want to implement a Decimation with D=6 to decimate from 5Mhz to 833Khz, but all the 833Khz content is with interest, so the priori low-pass filter seem to have a very sharp transition width, which is hard to implement. so anyone got some ideas?

## Sigma Delta - Decimation Filter Design

Started by in comp.dsp9 years ago 9 replies

I am designing filter to do decimation at the output of a Sigma Delta modulator. Here is the spec - Sampling frequency - Fs -...

I am designing filter to do decimation at the output of a Sigma Delta modulator. Here is the spec - Sampling frequency - Fs - 1.4MHz Decimation factor - D - 100 Input - 3 bits Output resolution - 13 bits. The filter, and the modulator are reset every 100 clock cycles. I tried using a CIC filter, but since it is to be reset every 100 clock cycles, I am limited to order 1. I will not ge...

## is there easy way to know which decimation phase got selected?

Started by in comp.dsp8 years ago 1 reply

Assume that i am doing decimation by 64, first by filtering and then throwing. This is implemented the same way in RTL and C. But there might...

Assume that i am doing decimation by 64, first by filtering and then throwing. This is implemented the same way in RTL and C. But there might be a data shift in input. Maybe one more or one less. This would essentially be same as selecting a different phase of the filter. Assuming that the input I feed is sine wave, is there a way to know which phase got selected? Observability points are o...

## Interpolation and decimation

Started by in comp.dsp15 years ago 44 replies

Hello, i am looking for decimation and interpolation technique in order to, given a sampling rate fs, obtain a new sampling rate like...

Hello, i am looking for decimation and interpolation technique in order to, given a sampling rate fs, obtain a new sampling rate like (a/b)*fs. A way to to do is to decimate and then use linear interpolation... Is there some other ways (documents) to do this ? If so, have you got some book or url ? Thanks

## Cascaded integrator comb decimation filter

Started by in comp.dsp8 years ago 2 replies

HI, Im new to DSP. Am now creating the CIC decimator. But my design has an error in the matlab although Hogenauer pruning was use. I works fine...

HI, Im new to DSP. Am now creating the CIC decimator. But my design has an error in the matlab although Hogenauer pruning was use. I works fine for decimation rate 6 and 10, for 3 and 2 have the "noise" occurs.. I dont know which is correct as I comparing VHDL and Matlab. The below is my matlab code: load Pulse100nsSigned.DAT D = 2; % Differential delay R = 2; % Downsampler delayBuffer1 = ...

## FIR Filter

Started by in comp.dsp11 years ago 5 replies

Hi, I have sampled the sinosoidal signal of 200Mhz at a rate of 500Mhz and i made decimation by factor of 25 on the above samples.The o/p of...

Hi, I have sampled the sinosoidal signal of 200Mhz at a rate of 500Mhz and i made decimation by factor of 25 on the above samples.The o/p of decimation is 20 mhz signal..I passed the above signal to a Digital bandpass filter( 198mhz--202Mhz).Later if i take the absolute value of the filter op ..what will be the output...whether it will be a sine wave or a constant DC(video)..pls help me in th...

## Root raised cosine decimation

Started by in comp.dsp11 years ago 1 reply

Hi, I have a root raised cosine in a receiver whose input is a 16x oversampled signal. How do I do the decimation at the output, or how to find...

Hi, I have a root raised cosine in a receiver whose input is a 16x oversampled signal. How do I do the decimation at the output, or how to find with sample out of 16 to keep? Is there any site or book where I can find information about this. Thanks

## Decimation filtering using Frequency response masking technique

Started by in comp.dsp15 years ago 4 replies

Hi, Can anyone please explain how decimation using frequency response masking is done?? thanks in advance. Raj.

Hi, Can anyone please explain how decimation using frequency response masking is done?? thanks in advance. Raj.

## CIC filter

Started by in comp.dsp11 years ago 8 replies

I read in one of the literature about a CIC filter with decimation of 3.5. As far as I know CIC decimates by integer only. Is there a way to...

I read in one of the literature about a CIC filter with decimation of 3.5. As far as I know CIC decimates by integer only. Is there a way to build a CIC with decimation of 3.5 ? Tom

## Standard filters for interpolation/decimation?

Started by in comp.dsp15 years ago 2 replies

I'd really like not to reinvent the wheel for my current hobby project, so I beg of all DSP people out there - what are the standard filters...

I'd really like not to reinvent the wheel for my current hobby project, so I beg of all DSP people out there - what are the standard filters used for 16X interpolation/decimation? Are they windowed-sinc, Chebyshev, Butterworth, or something else? And what are the coefficients, can I find tables of them somewhere? My goal is to create a simple VST guitar distortion plugin which uses non-lin...

## Help Understanding - Decimation, Anti-Alias and Accuracy !

Started by in comp.dsp15 years ago 1 reply

Hi, I have a problem, I have a oversampled (OSR =16) Digital Signal, prior to downsampling a filter is used, a 16 Tap BandpassFIR filter...

Hi, I have a problem, I have a oversampled (OSR =16) Digital Signal, prior to downsampling a filter is used, a 16 Tap BandpassFIR filter wich also have a Window. 1. Is there a document or approch how to calculate mathematically the resolution / Accuracy after the Filter, the Window and after the Decimation. (Filterquantisation ?) What errrors come from the Window ?? What role does ...