Publicité
Direct Digital Synthesis
The Keysight 33210A uses a signal-generation technique called Direct Digital
Synthesis (DDS) for all waveform functions except pulse. As shown below, a stream
of digital data representing the desired waveform is sequentially read from
waveform memory and is applied to the input of a digital-to-analog converter
(DAC). The DAC is clocked at the function generator's sampling frequency of 50
MHz and outputs a series of voltage steps approximating the desired waveform. A
low-pass "anti-aliasing" filter then smooths the voltage steps to create the final
waveform.
Address
Direct Digital Synthesis Circuitry
The 33210A uses two anti-aliasing filters. An elliptical filter is used for continuous
sine waves because of its nearly flat passband and sharp cutoff above 10 MHz.
Since elliptical filters exhibit severe ringing for waveforms other than continuous
sine waves, a linear-phase filter is used for all other waveform functions.
For standard waveforms, the function generator uses waveform memory that is
equivalent to 16,384 (16K) words deep. For optional arbitrary waveforms, the
function generator uses waveform memory that is equivalent to 8,192 (8K) words
deep.
Keysight 33210A User's Guide
Waveform
Memory
Data
Waveform
DAC
50 MHz
Tutorial
Anti-Aliasing
Filter
7
343
Publicité
