Table of Contents
Advertisement
3
Using the Instrument
Generating Modulated Waveforms
Figure 3-26, User PSK Data Entry Table Example
There are 4 different types of Quadrature Amplitude Modulation that
(n)QAM
the 2074 can generate: 16QAM, 64QAM and 256QAM. If another
constellation scheme is required, one can use the User QAM to
design his/her own symbol list and constellation. An example of a
64QAM display is shown in Figure 3-27.
There are other parameters that control the (n)QAM function, these
are:
QAM Type – selects from one of 16QAM, 64QAM, 256QAM and
User QAM. Once a type is selected the associated parameters are
automatically available on the display for adjustments.
QAM Data – provides access to the QAM data symbols. By default
the table is empty so the symbols must be loaded into the table
before the (n)QAM function can be used. For testing and/or
demonstration purpose, a default table is available to download
from the front panel however, this table must be converted for
different applications. An example of the 64QAM data entry table is
shown in figure 3-28.
CW Control – can turn the carrier waveform on and off. Use the
carrier off position when directly driving vector generators.
CW Frequency – defines the frequency of the carrier waveform.
Using this QAM function, the shape of the carrier waveform is
always sine. CW frequency is programmable from 10 Hz to 50 MHz.
Symbol rate – programs the rate of which symbols step through.
The rates can be programmed from 1 symbol/s to 1e6 symbols/s.
Marker – defines an index point where the SYNC output generates
a synchronization pulse. The marker can be programmed within the
range of the symbol list.
3-49
Advertisement
Table of Contents
