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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?! ...

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...

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...

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...

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...

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...

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 ...

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...

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...

Please help me in understanding "Decimation filter"

Hi All, I thank all of you, for your support, which I got previously. I am hardware design engineer and working on sigma delta ADC. And my role is to design decimation filter, basically I have to design a blocks which converts single bit to multi bits output. I surveyed lots of literature. ...

Multirate filter design

Hello All, The task is to design the multiple cascaded FIR filters to do the decimation. There are tough requirements about the resultant ripples in the passband; the stage-by-stage design seems to be very inefficient. Can you suggest a filter design software which can optimize the overall...

Dumb Decimation Technique?

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 ->...

Help Understanding - Decimation, Anti-Alias and Accuracy !

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 af...

FFT By Decimation In Time paper or succinct explanitory resource

Hi All, I have recently completed my DSP course (subject) which is part of my engineering degree and I am very interested in DSP applications to Audio in particular. I have decided to undertake a project which involves FFT (probably I will use a Radix-2 to keep it simple for me) in hardware...

best method for implementing an SRC

Hi, i would like to know which is the best method for implementing a integer sample rate converter (decimation /interpolation) in terms of quality. the conversion rates required are (2,4,8,16) both decimation and interpolation.i had tried with polyphase implementation and lagrange interpolatio...

Re: Is it possible to decompose FFT to accept input in sampling time?

Jimm Avante wrote: > I am new to FFT but after reading, all FFT starts butterfly operation during > the > middle of the frame. For example, a radix-2, it starts until N/2 sample has > been > read in from ADC, i.e. but(0, N/2-1), but(1, N/2), ... > > Is it possible to design it in su...

ADI decimation function

Been looking at the ADI library, specifically fir_decima FIR-based decimation filter Synopsis #include float *fir_decima (const floatinput[], floatoutput[], const float pmcoefficients[], floatdelay[], intnum_output_samples, intnum_coeffs, intdecimation_index); Description The fir_...

Testing Digital Filter

Hello, I am using Linear feedback shift register(LFSR) to test Digital filter(DF) because LFSR generate white noise and has a flat like spectrum. Can anynody suggest when I pass white noise in DF, on what citeria should I judge the filter (Device Under Test) is pass or fail ?? my fi...

Help me to understant sampling theory, decimation by integer factor

Hi, everyone! I read "decimation by integer" and "interpolation by integer factors" in a DSP book. I'm just wondering why integer factor to downsampling... Sometimes, to resample signal by rational factor, people use conversion oversampling(integer factor) -> low-passfilter -> dow...

poor constellation after CIC filter

I am trying to simulate a rational sample rate conversion architetcure using CIC filters (decimation) and farrow structure (interpolation). Input data is QPSK modulated and upsampled by a large factor (325 to be exact). I try to decimate the signal by 125 in three stages. each stage is in turn a C...

FFT: decimation in freq vs dec in time?

Could someone please refer to good, non-matematician-accessible discussion of decimation-in-time vs decimation-in-freq FFT's? Second, more confused, question. The implementations I find online are d.in-time, but I'd like a d.in-freq implementation if available (i think). The idea is to build ...

Re: A way of demodulating BFSK

"glen herrmannsfeldt" wrote in message news:R_qdneUT0d873YfYnZ2dnUVZ_s6dnZ2d@comcast.com... > Tim Wescott wrote: > > > > Your biggest stumble is that you aren't synchronizing to > > the bit rate. You should sample at the point where your > > filters' outputs peak for any given b...

decimation filter (is this normal)??

Hi everybody, I am designing a decimation filter for a 16bit delta-sigma A/D. The decimator will be a CIC decimate by 16 filter, followed by two FIR filters to get the required attenuation. I have two questions as most of my experience is in analog & not digital design. 1- The filter ord...

irrational factor decimation

Thanks for the guys who aswered my decimation question, howver I am really looking for irrational decimation, so I am clearing up the confusion: I am trying to decimate bandlimited data by an irrational factor like Tin/Tout = 2*sqrt(2) where Tout and Tin are the output and input sampling tim...