Keysight EXG and MXG X-Series Signal Generators User’s Guide
409
Custom Digital Modulation (Option 431)
Differential Encoding
This encodes the first symbol by adding a symbol table offset of 1. The symbol rotates
forward
through the state map by 1 value when a data value of 0 is modulated.
2.
Press
+/–
>
1
>
Enter
.
This encodes the second symbol by adding a symbol table offset of
-
1. The symbol rotates
backward
through the state map by 1 value when a data value of 1 is
modulated.
3.
Press
2
>
Enter
.
This encodes the third symbol by adding a symbol table offset of 2. The symbol rotates
forward
through the state map by 2 values when a data value of 10 is modulated.
4.
Press
0
>
Enter
.
This encodes the fourth symbol by adding a symbol table offset of 0. The symbol does
not
rotate through the state map when a data value of 11 is modulated.
Applying Custom Differential Encoding
Press
Return
>
Differential Encoding Off On
.
This applies the custom differential encoding to a user–defined modulation.
At this point, the modulation has one bit per symbol. For the first two data
values (00000000 and 00000001) only the last bits (the 0 and the 1,
respectively) are significant.
At this point, the modulation has two bits per symbol. For the data values
00000000, 00000001, 00000010, 00000011, the symbol values are 00, 01,
10, and 11 respectively.
Notice that
(UNSTORED)
appears next to
Differential State Map
on the
signal generator’s display. Differential state maps are associated with the
user–defined modulation for which they were created.
In order to save a custom differential state map, you must store the user–
defined modulation for which it was designed. Otherwise the symbol table
offset data is purged when you press the
Confirm Exit From Table Without
Saving
softkey when exiting from the I/Q or FSK table editor.
