DIGITAL MODULATION MODE
3-31
Data/timing
The
[Data/Timing]
key on the
Sig Gen
menu is used to select the modulating data source and to
define the bit clock and symbol clock operation. Pressing the
[Data/Timing]
key causes the
Data/Timing Control Menu
shown in Fig. 3-28 to be displayed (this key is not available in test
tone mode).
Data Source : External Serial
Data Polarity : NORMAL
Bit Clock
: INTERNAL (+ve. edge)
Symbol Clock : INTERNAL (+ve. edge)
LOCAL
Data
Polarity
External
Serial
External
Parallel
Select
Internal
Int/Ext
Bit Clk
Int/Ext
Sym Clk
Sym Clk
Polarity
Bit Clk
Polarity
C0846
Data / Timing Control Menu
Fig. 3-28 Digital modulation: Data/Timing control menu
Data
Data input may be selected between external i.e. connected to the rear panel AUXILIARY
IN/OUT connector, and internal i.e. generated by the instrument as follows:
For external data input select either serial or parallel data by pressing either the
[External Serial]
or
[External Parallel]
key. Note that the soft keys controlling the bit clock are suppressed for
parallel data operation. For the modulation data contact assignments for the rear panel connector
see Table 2-1.
To change the data polarity press the
[Data Polarity]
key which toggles between normal and
inverse polarity.
For internal data generation press
[Select Internal]
which displays a further menu (see Fig. 3-29
below).
For details on how data is mapped on the RF carrier see 'Digital data mapping' below.