## Forums Search for: Quantizer

## ADC quantizer question.

inHello, I am looking for some facts or specifications about an ADC quantizer. Firstly I want to know if it possible for quantizers to...

Hello, I am looking for some facts or specifications about an ADC quantizer. Firstly I want to know if it possible for quantizers to dynamically change their resolution? or is it fixed for a quantizer. If the quantizer can actually change its resolution, I would be very grateful if somebody could direct me to a site or a article about this mechanism. Specifically; 1) The connection between...

## Adaptive Equilization

inI'm looking at the block diagram on page 247 of "Adaptive Signal Processing" from B.Widrow and S.D.Stearns. Anyway, the block diagram shows an...

I'm looking at the block diagram on page 247 of "Adaptive Signal Processing" from B.Widrow and S.D.Stearns. Anyway, the block diagram shows an LMS filter in the center, and the Quantizer on the bottom right. The output of the Quantizer goes to a subtraction element (which subtrats the LMS output from the Quantizer), then the output goes to the "Gate". First, what is the output of the Q...

## adaptive quantization and transmission errors

inHi I am working on a backward adaptive non-uniform quantizer for use in wireless transmissions. More precisely my quantizer currently consists...

Hi I am working on a backward adaptive non-uniform quantizer for use in wireless transmissions. More precisely my quantizer currently consists of an adaptive compader (currently atan-based) and a simple uniform quantizer. This works very well. Trouble is: I am going to transmit data over a noisy wireless channel. As of now the errors are bringing the adaptive expander on the decoder side ...

## How determine the path of signal?

inI am digitizing the sampled signal be using a uniform quantizer, so the step (q) between two consective quantization levels is fixed and is "q...

I am digitizing the sampled signal be using a uniform quantizer, so the step (q) between two consective quantization levels is fixed and is "q = Vin/2^N" where 'q' is the quantization step, 'Vin' is the total range of quantizer and 'N' are the effective number of bits of quantizer. Now I want to determine the path which the signal is following between two consective quantization levels. i.e wea...

## snr of quantizer using fixed logic

inHello all, I am doing SNR measurement of 8 bit quantizer implemented using "fix" logic (flooring towards zero for both +...

Hello all, I am doing SNR measurement of 8 bit quantizer implemented using "fix" logic (flooring towards zero for both + and - numbers). i am doing time domain and frequency domain estimation. TSNR = 43.6 dB (correct value). FSNR = 48.0 dB (in-correct value). for all other quantizers like round, floor and ceil, i get the same ...

## LLR quantizer

inHi, Can someone explain how to quantize LLRs values (which are real numbers) to finite precision i.e. discrete soft bit. I know that Es/No has...

Hi, Can someone explain how to quantize LLRs values (which are real numbers) to finite precision i.e. discrete soft bit. I know that Es/No has impact on quantizer boundaries but I just dont understand how to map correctly LLRs to discrete soft bit to maximize the decoder performance. This is because LLRs could be very small or very high values in dependence of Es/No. I also know fact that gener...

## Noise Shaping and Clipping

inConsider a requantization system with noise shaping and dithering. The question is what to do when the sum of the signal, the noise feedback...

Consider a requantization system with noise shaping and dithering. The question is what to do when the sum of the signal, the noise feedback and dither exceeds the range of the output quantizer. A differentiator of the Nth order used as a noise shaping filter has the max. feedback of ~2^N. So it is quite likely that the quantizer will run out of range at or near the peak values of the in...

## uniform scalar quantizer

inHow does one design the optimum uniform scalar quantizer for a specific Gaussian input? All the literature I can find on quantization seems to...

How does one design the optimum uniform scalar quantizer for a specific Gaussian input? All the literature I can find on quantization seems to deal with analyzing specific quantizers, quantization noise probability densities and power spectra etc., but I cannot seem to find any specifics on just the design - selecting delta. I have seen it derived under entropy constraints, but I would ...

## The optimal quantization

inHi, Anybody knows who and where works in optimal quantization area? Max Lloyd quantizer was created 50 years ago. What is going on this...

Hi, Anybody knows who and where works in optimal quantization area? Max Lloyd quantizer was created 50 years ago. What is going on this scientific direction now?

## Sigms Delta Modulator Question

Hi all, If input a step respond into a SDM with a 1 bit quantizer, the output would be a stream of '1' and '0' s. IS that stream PCM or...

Hi all, If input a step respond into a SDM with a 1 bit quantizer, the output would be a stream of '1' and '0' s. IS that stream PCM or PDM?? Can I tell the dynamic range form the bit stream?? For example a 50nA step input with a output bit strem of "101010111011" and repeat. what can I tell from these stream?? Say if I use a 1:12 decimation average =8/12 0.6667 Does that m...

## how can I decide the points of blackman window?

Hi:all I am trying to measure the SNR of a second order sigma-delta ADC. I want to just do a FFT analysis for the output of the quantizer. So,...

Hi:all I am trying to measure the SNR of a second order sigma-delta ADC. I want to just do a FFT analysis for the output of the quantizer. So, I collect 65536 points for FFT. I was told that I should use a Blackman window here.But how many points of the blackman window should I use? Here are some specs: sample frequency:12.5MHz Baseband frequency:20KHz Input signal freq:1000Hz Is there any...

## How can I decide the blackman window's points ?

inHi:all I am trying to measure the SNR of a second order sigma-delta ADC. I want to just do a FFT analysis for the output of the quantizer. So,...

Hi:all I am trying to measure the SNR of a second order sigma-delta ADC. I want to just do a FFT analysis for the output of the quantizer. So, I collect 65536 points for FFT. I was told that I should use a Blackman window here.But how many points of the blackman window should I use? Here are some specs: sample frequency:12.5MHz Baseband frequency:20KHz Input signal freq:1000Hz Is there ...

## Functioning of a second order Sigma delta modulator

inHello All, I am a newbie to the Sigma Delta domain. I am trying to simulate a sigma-delta modulator(SDM) (2 order, using 1 bit quantizer)...

Hello All, I am a newbie to the Sigma Delta domain. I am trying to simulate a sigma-delta modulator(SDM) (2 order, using 1 bit quantizer) but have been running into troubles all the way along. 1. using a straight forward implementation of the second order SDM as shown by BOSER and WOOLEY, the program shows a decrease in the SNR ratio for a 2nd order. A theoritically calculated value i...

## Delta-Sigma Modulator question

inDear all, In a Delta-Sigma Modulator, after the quantizer, the output bit stream (+1 and -1) is fed back to the input and being subtract from...

Dear all, In a Delta-Sigma Modulator, after the quantizer, the output bit stream (+1 and -1) is fed back to the input and being subtract from the input(assuming first order loop). However, none of the references that I read mentioned how large this feedback signal should be. For example, if the input is limited within +-1, how larger this feedback signal should be? Also +-1? I did some exp...

## Sigma Delta - Modeling s-function

inHey guys, I have a continuous-time sigma-delta converter that includes a continuous-time transfer function H(s) at the input, followed by...

Hey guys, I have a continuous-time sigma-delta converter that includes a continuous-time transfer function H(s) at the input, followed by a sampler, quantizer and a digital-to-analog converter (DAC) in the feedback path. I'm trying to model the transfer function H(s) that includes some non-ideal effects and hence, the order of H(s) is higher than that of the system (say for the second-ord...