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Quantization noise

From Biocrawler, the free encyclopedia.

Quantization noise is a noise error introduced by the analogue to digital conversion (ADC) process in telecommunication systems and signal processing. It is a rounding error between the analogue input voltage to the ADC and the output digitized value. The noise is additive and independent of the signal when the number of bits $Q$ is greater than 4, i.e. more than 16 digitizing levels, $L = 2 Q$ .

It is expressed as a root-mean-square error as

$N_Q = \frac{ \left ( \frac{V_{AD}}{2^Q} \right )^2 }{6 \cdot T_S \cdot R_L^2}$

where $V A D$ is the analogue voltage range of the converter (Volts), $Q$ is the number of bits of the converter, i.e. resolution of the converter, $T S$ is the sample interval of the converter (seconds), and $R L$ is the load resistance of the converter (Ohms).

In an ideal analogue-to-digital converter, the signal-to-noise ratio (SNR) in defined as

$SNR_{ADC} = Q \cdot \left ( 1.763 + 6.02 \right )$ dB