At this time, DMT modulated waveforms are not typically menuselectable
items contained within arbitrary waveform generators.
Even using AWG software to generate DMT signals, AWGs that
are available today may not deliver DMT signals sufficient in
performance with regard to MTPR due to limitations in the D/A
converters and output drivers used by AWG manufacturers.
Similar to evaluating single-tone distortion performance of an
amplifier, MTPR evaluation requires a DMT signal generator
capable of delivering MTPR performance better than that of the
driver under evaluation. Generating DMT signals can be accomplished
using a Tektronics AWG 2021 equipped with opt 4,
(12/24-Bit, TTL digital data out), digitally coupled to Analog
Devices AD9754, a 14-bit TxDAC?, buffered by an AD8002
amplifier configured as a differential driver. See Figure 45 for
schematics of a circuit used to generate DMT signals that can
achieve down to –80 dBc of MTPR performance, sufficient for
use in evaluating xDSL drivers. Note that the DMT waveforms
available with the AD8016ARP-EVAL and AD8016ARB-EVAL
boards or similar WFM files are needed to produce the necessary
digital data required to drive the TxDAC from the optional
TTL digital data output of the TEK AWG2021. Copies of these
WFM files can be obtained through the Analog Devices website,