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i'm sorry...what's decimation?

hi! i'm sorry what is decimation? yesterday, i found a block diagram of digital signal processing for demodulate AM signal... and there is a decimation process after the balance modulator... i don't understand the function of decimation process... please, help me... thank you... -c1910-...

Question about Z transform of decimation

Hi, I am learning about digital decimation. The problem is like this: Z-transform of input sequence and filter aree X(z), H(z) respectively. After the filter H(z), there is a 2 decimation. From one book talking about decimation, it says the Z-transform of output sequence after decimation is: ...

Decimation for demodulation

hi! i want to demodulate AM signal with DSP...i found an article that says like this : demodulator is illustrated as decimation integration filter. It includes a multiplier portion and an integration/decimation portion. so can we demodulate AM using decimation method? and what is decimatio...

i'm sorry...what's decimation?

hi! what is decimation? can everybody give me an example? or the definition? or what is the function? thanks, coz i don't understand the decimation?! ...

decimation filter problems

Hi, I have 2 questions about decimation filter for a SD ADC. Firstly, how is the relationship between SNR and stopband attenuation for decimation filter. For example if I have 14 bits output of the decimation filter, SNR=(6.02*N+1.76)=86 db, so will I choose stopband attenuation > 86 db for decim...

multirate implementation on fix point DSP and efficiency

Hye, I have a question to try to find a way to improve my processing. I use a multirate filter with decimation. There is a decimation by 40. One FIr is used then decimation, and the 1 IIR with decimation, then a second IIR with decimation, then again oner IIR and decimation and at last one F...

Decimation design

Hello, I am looking for good advices about my design. I am working with an ADC which work beetween 1kHz and 2kHz but the application need data sampled beetween 10 Hz and 2 kHz. So i decide to make decimation in order to get the sample frequence beetween 10Hz and 1 kHz. But in order to do it...

Multirate Filter

Rick Lyons wrote: > It took me a while to find the darned post of mine. > My post was: > > From: R.Lyons@_BOGUS_ieee.org (Rick Lyons) > Subject: Re: Multirate filter design > Date: Tue, 11 Jul 2006 10:45:44 GMT > I remember reading (somewhere) that it is *VERY* > difficu...

Decimation / downsampling

Hello, I have problem puting the rigth name on the rigth thing: --> In "Discrete-time signal processing" of Oppenheim and schafer : "In general, the operation of reducing the sampling rate (including any prefiltering) will be called downsampling" section 4.6.1 --> In "An overview of sig...

CIC decimation filter

I need to implement a decimation filter( using CIC structure )in C. I have created integrator block,another block for decimation and finally a third block for comb structure and cascaded them in that order.But the final frequency response doesnot match the theoretical graph.I have used 2's complime...

decimation by dropping two samples

Hi All, I was analyzing a decimation scheme where two samples are dropped alternatively . 0,1 are picked 2,3 are dropped , 4,5 are picked and 6 and 7 are dropped and so on. I have never seen such a decimation scheme . I would like to know whats the advantage of the this scheme. An...

Sigma Delta - Decimation Filter Design

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 CI...

Re: Polyphase decimation

Praveen wrote: > Hi > > I am implementing a polyphase decimation of a 8k signal by a factor of > 20. I have designed a filter of pi/20, which means there are 20 > subbands. In case of decimation, the input gets shifted by a sample at > each time instant and then convolved with all the...

Increase resolution through decimation

Hi I need to take a standard 8bit ADC which samples at 40Msps increase the resolution by about 4 or 5 bits. I know that oversampling spreads the quantization noise over a wider bandwidth thereby decreasing the SQNR. So i can increase the resolution through decimation? How do I increase the resolu...

Question for bit number decision of decimation filter's output

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/...

Decimation (CIC) filter in VHDL

Hi all, I am currently in the process of designing a decimation filter for a 16bit Sigma Delta ADC. I suspect it will be a CIC filter followed by a FIR filter. I am facing great difficulty understanding such filter, as my experience in usually with analog circuits, and not DSP. My ques...

fir decimation filters

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

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 hol...

Re: FFT Radix

I have not heard of mixed radix. but split radix is when you use both radix2 and radix4 to compute N point FFT. your output or input ordering/reordering will depend on if you are implementing decimation in time or decimation in freq algo. if you are doing decimation in time then you have to re...

Re: Multistage interpolation question

Hi Guys, Wow. Thanks for all the replies. You've given me a lot to think about. One of the things that prompted my question is the fact that if we need to decimate by a large factor D, we can decimate in two stages (decimate by D1, followed by decimation by D2) to reduce the overa...

Interchanging FIR and Decimation operation

Hi all, I have a yet another decimation question rather a decimation and a FIR filter question. I have 64K input samples that are filtered using a 3 tap - 2nd order FIR filter, say [a1 a2 a3]. After filtering they are decimated by 8. I want to reverse this operation such that I decimate fi...

decimation filter delay

Hi members I am new to multirate dsp ,I understand that to down sample you need to have antialias filter bandlimited to Fs/2(Fs output sampling rate)and take the M (decimation factor)samples and discard M-1 samples. My questions are 1)Is antialias filter itself called decimation filter 2) delay...

Fractional decimation

Hello, I've been studying polyphase decomposition, decimation, interpolation and fractional decimation. I think I have a handle on what I'm doing, but there's one thing I don't understand... Do you have to have greater than an L*Mth order filter in order to use polyphase decomposition to put t...

How to implement an efficient ALL-PASS decimation?

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? ...

Interpolation and decimation

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 boo...

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

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 inp...

easy resampling bandwith question ...

hi all, let's say i want to resample to 4/5 the input samplerate, i.e. interpolate 4X then decimate 5X. for both steps lowpass filters need to be designed. according to dspguru.com, it is sufficient to 1. determine cutoff freq. for the interp. filter 2. determine cutoff freq. for the dec...

decimation alias

I'm usig CIC5 decimation filter, which is part of a larger signal processor chip, decimation is M=8, the input frequency is Fs. Since CIC filters only have infinite attenuation at f=Fs/8*k , k={1..7}, a considerable amount of Alias will 'fold' into the output data stream's spectrum between 0...Fs/16...

Root raised cosine decimation

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

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

CIC filter

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 ...

FIR Filter

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 ..w...

Re: Fast down sample filtering

Eric Jacobsen wrote: > On 12/9/2009 7:54 AM, km wrote: > > Hi All, > > Does anyone have a suggestion for a fast down sampling filter? > > For N:1 reduction, add N consecutive samples together and output that. > Move to the next window of N samples. > > The response will not be...

Re: frequency respons of halfband filter?

All thanks for attempts to help me but I have not understood where I am mistaken. Let's try to ask a question easier and particularly. Let's assume at us there is a system consisting of the filter and following for it decimation. The impulse response of filter H=[0.033402 0 -0.015082 0 0...

Decimate by 2 - DDC FI at 3fs/4

Hello, I am studying a DDC working with FI = 3fs/4, and I have something that I don't understand for the quadrature demultiplexing. Here are the steps of the quadrature downconversion of the studied system : 0) The signal at FI is sampled at Fs. This is what I receive in my DDC 1) The centr...

Re: Decimation filter: Output magnitude response

> > analog_fever wrote: > > > > > I have a decimation filter which decimates by 100. > > > > > Input sampling frequency fclk1 = 1.6MHz, > > > Output Sampling freq flck2 = 16kHz. > > > > > For the input, I use fft function in matlab, and get the magnitudes of > my > > > frequency resp...

Question about Sigma-Delta conversion/decimation

Hi all, My question is related to sigma-delta conversion. I understand the analog side of this, i.e. the modulator, and have developed a matlab simulation which gives me 1's and -1's output for any input signal. Essentially, this is the high data rate 1 bit output of the sigma delta modulato...

How to obtain X(z^1/2) from X(z)

Dear all, I have a question linked to the decimation of a signal. Let's have a signal x(n), and X(z) its Z-transform. If we decimate this signal, i.e. xe(n) = x(2n), we obtain the following Z-transform : Xe(z) = 1/2 [X(z^1/2) + X(-z^1/2)] My question is : is there a way to obtain a signal ...

Basic question on upsampling/downsampling

Hi, I am new to DSP and learning about sampling and related topics. I have read a book and visited online sites but still am having problems understanding : 1. Why do we need a filter (FIR) BEFORE we downmsample when we perform decimation. I understand why for upsampling we need the filtering ...

Chroma Decimation in Digital Video Signals

Hi, I've seen several cases where the chroma decimation, e.g., when going from YCrCb 4:4:4 to 4:2:2, is done by simply throwing away every other sample. I have two questions regarding this operation: 1. If there were a 1-D signal, simply throwing away every other sample without first f...