adcresolutionsignal
This is a question from this application note:
http://www.atmel.com/images/doc8003.pdf
In section 3.2 on noise it says that adding some amount noise into the signal helps in increasing the resolution of the oversampling converter. It says if LSB toggles due to noise and we are averaging 4 of the samples then the quantization step is halved. I do not understand how is the quantization step becomes half. Could anyone explain this?
The 1.22mV is the step size, sometimes also called LSB. Take a look at this google search.
Step size:
Step size is the minimum change in input voltage which can be resolved by the ADC. The concept of step size is closely associated with the resolution of ADC.
Resolution:
The resolution of an ADC refers to the number of bits in the digital output code of the ADC.
The relation between step size, resolution, and input range can be given by:
This picture here taken from analog devices app note MT-022 show why the delta sigma is better than just averaging and its all due to the Delta Sigma modulation that shapes the quantization noise in such fashion that is taken away from the band of interest. If the quantization noise goes down it means you can be more certain that your interpolation can be more granular as shown in figure C. while just filtering and decimation spread. So it all comes down to noise shaping provided by the Delta sigma modulation
Best Answer
Suppose you have a signal which is 1/4 they way between LSBs. With four noiseless samples you would just get four zeros.
With a slightly noisier signal, one fourth of those samples (1 on average) would actually get high enough to become a 1. The average of three zeros and a one becomes 1/4.
Similarly if it were closer to 1, you would get some smaller fraction of 0s.