## decimation filter problems

Started by in comp.dsp9 years ago 3 replies

Hi, I have 2 questions about decimation filter for a SD ADC. Firstly, how is the relationship between SNR and stopband attenuation for...

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 decimation filter? Secondly, if my input is 100 khz sinus, when I'm designing decimation filter will I

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

Started by in comp.dsp12 years ago 1 reply

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...

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

Started by in comp.dsp15 years ago 1 reply

Hi, I am learning about digital decimation. The problem is like this: Z-transform of input sequence and filter aree X(z), H(z)...

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: V(z)=(1/2)*[H(z^(1/2)*X(z^(1/2))+H(-z^(1/2)*X(-z^(1/2))] I have learned Z transform, but no Z tr...

## Decimation for demodulation

Started by in comp.dsp12 years ago 1 reply

hi! i want to demodulate AM signal with DSP...i found an article that says like this : demodulator is illustrated as decimation integration...

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 decimation integration filter? thank you...

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

Started by in comp.dsp12 years ago 5 replies

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...

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

Started by in comp.dsp14 years ago 2 replies

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...

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 FIr . I use a fix point DSP. The filter are designed in 16 bits inputs / outputs (32 bits for comp...

## Polyphase decimation

Started by in comp.dsp14 years ago 6 replies

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...

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 filters accordingly, and finally summed from all the subbands to give the output. And finally 19 out of 20 samples are thrown out....

## decimation alias

Started by in comp.dsp11 years ago 3 replies

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...

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. The CIC spectrum H(f) can be calculated easily between -Fs/2 ... Fs/2 according to the formula giv...

## Fractional decimation

Started by in comp.dsp11 years ago 2 replies

Hello, I've been studying polyphase decomposition, decimation, interpolation and fractional decimation. I think I have a handle on what I'm...

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 the compressor and expander in their most efficient places (first and last, respectively)? For exa...

## Increase resolution through decimation

Started by in comp.dsp12 years ago 3 replies

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...

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 resolution through decimation? It decimates the signal frequency but i don't physically know how to increa...

Started by in comp.dsp15 years ago 17 replies

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...

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. I referred "An Economical Class of Digital Filters for Decimation and Interpolation" by Eugine B H...

## Help on FIR decimation

Started by in comp.dsp6 years ago 16 replies

Hi all I have a FIR decimation code, which is meant to decimate audio from 44100 Hz to 11025. My problem is the output is complex, but I need to...

Hi all I have a FIR decimation code, which is meant to decimate audio from 44100 Hz to 11025. My problem is the output is complex, but I need to get this data back to real number, as the complex don't mean nothing to me. How do I do it? The author gives the following information: -- A 35-tap FIR decimation filter to frequency shift and subsample real fastsamps -- at 44100 samps/sec int...

## Interchanging FIR and Decimation operation

Started by in comp.dsp15 years ago 13 replies

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...

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 first and then filter it for obvious reasons (why should I compute the taps that anyways I am going ...

## CIC decimation filter

Started by in comp.dsp9 years ago 8 replies

I need to implement a decimation filter( using CIC structure )in C. I have created integrator block,another block for decimation and finally...

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 compliment notation,Q15 format. It shall be of great help if anyone has sample codes for this filter. ...

## FFT: decimation in freq vs dec in time?

Started by in comp.dsp15 years ago 2 replies

Could someone please refer to good, non-matematician-accessible discussion of decimation-in-time vs decimation-in-freq FFT's? Second, more...

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 a tree of partial FFT's: While making a 512-pt fft I want to save the intermediate 16 32-point fft'...

## irrational factor decimation

Started by in comp.dsp13 years ago 9 replies

Thanks for the guys who aswered my decimation question, howver I am really looking for irrational decimation, so I am clearing up the...

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 time. I am using a simple linear interpolator where coefficient changes at the output rate: y(m) = x(n...

## CIC Decimation Filter "zero crossing" distortion

Started by in comp.dsp2 years ago 6 replies

Hi, I am designing a simple decimation filter, with decimation rate at 5 (1st stage) and 20 (2nd stage). N=2 and 3 for each stage. Bin=1....

Hi, I am designing a simple decimation filter, with decimation rate at 5 (1st stage) and 20 (2nd stage). N=2 and 3 for each stage. Bin=1. Bout=16. Input Sampling frequency at 50 KHz and output at 500 Hz. The fixed point matlab simulation (2's complement) shows that with Sinewave input at 5Hz, there are a few "flat" "zero" crossing points in each sinewave cycle. I check t

## decimation by dropping two samples

Started by in comp.dsp8 years ago 13 replies

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...

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. And also will the sampling frequency change here ??

## decimation filter delay

Started by in comp.dsp11 years ago

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...

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 in FIR filter is given as (N-1)/2 (N. no of taps) ,what is the formula if I decimate by factor M, a...

## Decimation design

Started by in comp.dsp16 years ago 9 replies

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...

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 in the rigth way i make pre-filtering in order to avoid aliasing. So the decimation factor coul...