Keysight EXG and MXG X-Series Signal Generators User’s Guide
407
Custom Digital Modulation (Option 431)
Differential Encoding
When applied to the user–defined default 4QAM I/Q map, starting from the 1st symbol (data 00),
the differential encoding transitions for the data stream (in 2–bit symbols) 0011100001 appear in
the following illustration.
As you can see from the previous illustration, the 1st and 4th symbols, having the same data value
(00), produce the same state transition (forward 1 state). In differential encoding, symbol values do
not define location; they define the direction and distance of a
transition
through the I/Q State
Map.
Using Differential Encoding
The signal generator’s
Differential State Map
table editor enables you to modify the
differential state map associated with user–defined I/Q and user–defined FSK modulations. In this
procedure, you create a user–defined I/Q modulation and then configure, activate, and apply
differential encoding to the user–defined modulation. For more information, see
Configuring User–Defined I/Q Modulation
1.
Press
Preset
.
2.
Perform the following keypress sequence required for your format type.
For Custom ARB Format
Press
Mode
>
ARB Custom Modulation
>
Single Carrier Setup
>
Modulation Type
>
Select >
More 1 of 2 > Define User I/Q
>
More > Load Default I/Q Map
>
QAM
>
4QAM
.
Or this alternate sequence:
Data Value
Symbol Table Offset
00
01
10
11
+1
–1
+2
+0
Data = 0011100001
{
{
{
{
{
5th Symbol
1st Symbol
3rd Symbol
4th Symbol
2nd Symbol
1st
2nd
3rd
5th
4th
