O'Reilly logo

Digital Audio Signal Processing, Second Edition by Udo Zölzer

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

Chapter 3

AD/DA Conversions

The conversion of a continuous-time function x(t) (voltage, current) into a sequence of numbers x(n) is called analog-to-digital conversion (AD conversion). The reverse process is known as digital-to-analog conversion (DA conversion). The time-sampling of a function x(t) is described by Shannon's sampling theorem. This states that a continuous-time signal with bandwidth fB can be sampled with a sampling rate fS > 2fB without changing the information content in the signal. The original analog signal is reconstructed by low-pass filtering with bandwidth fB. Besides time-sampling, the nonlinear procedure of digitizing the continuous-valued amplitude (quantization) of the sampled signal occurs. In Section 3.1 basic concepts of Nyquist sampling, oversampling and delta-sigma modulation are presented. In Sections 3.2 and 3.3 principles of AD and DA converter circuits are discussed.

3.1 Methods

3.1.1 Nyquist Sampling

The sampling of a signal with sampling rate fS > 2fB is called Nyquist sampling. The schematic diagram in Fig. 3.1 shows the procedure. The band-limiting of the input at fS/2 is carried out by an analog low-pass filter (Fig. 3.1a). The following sample-and-hold circuit samples the band-limited input at a sampling rate fS. The constant amplitude of the time function over the sampling period TS = 1/fS is converted to a number sequence x(n) by a quantizer (Fig. 3.1b). This number sequence is fed to a digital signal processor (DSP) which performs signal ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required