Direct Digital Synthesis
Digital signal processing methods are used in many everyday
applications. Whether it is a digital audio compact disc player, an
electronic synthesized piano, or a voice-synthesized telephone message
system, it is obvious that complex waveforms can be easily created or
reproduced using digital signal generation methods.
The 33120A uses a signal-generation technique called direct digital
synthesis or
DDS. The basic principle behind DDS is not unlike an audio
compact disc. As shown below for digital audio, a stream of digital data
representing the sampled analog signal shape is sequentially addressed
from a disc. This data is applied to the digital port of a digital-to-analog
converter (
DAC) which is clocked at a constant rate. The digital data is
then converted into a series of voltage steps approximating the original
analog signal shape. After filtering the voltage steps, the original analog
waveshape will be recovered. The incoming data can be of any arbitrary
shape, as long as it matches the requirements of the particular
DAC
(16 bits for digital audio players).
D-to-A
Converter
Data
Anti-Alias Filter
A
7
Chapter 7 Tutorial
Direct Digital Synthesis
273
To Next Page
Loading...
Need help?
General
