Multirate Digital Signal Processing, Oversampling of Analog-to-Digital Conversion, and Undersampling of Bandpass Signals - Digital Signal Processing: Fundamentals and Applications - page 586

f s
2 f max >> 1

(12.14)

The benefits of an oversampling ADC include

1. helping to design a simple analog anti-aliasing filter before ADC, and

2. reducing the ADC noise floor with possible noise shaping so that a low-resolution

ADC can be used.

12.3.1 Oversampling and Analog-to-Digital Conversion Resolution
To begin developing the relation between oversampling and ADC resolution, we first summarize the
regular ADC and some useful definitions discussed in Chapter 2:

2
12

q ¼ D

2

Quantization noise power ¼ s (12.15)

Quantization step ¼ D ¼ 2 n

(12.16)

where A ¼ full range of the analog signal to be digitized and n ¼ number of bits per sample (ADC
resolution).
Substituting Equation (12.16) into Equation (12.15) , we have

2
12 2 2 n

q ¼ A

2

Quantization noise power ¼ s (12.17)

The power spectral density of the quantization noise with an assumption of uniform probability
distribution is shown in Figure 12.23 . Note that this assumption is true for quantizing a uniformly

n-bit ADC

f s

2

q

f

s

f s
2

f s
2

2

q

2

P f df () area f

q s

f

s

FIGURE 12.23

Regular ADC system.