366 Agilent X-Series Signal Generators User’s Guide
Custom Digital Modulation (Option 431)
Differential Encoding
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 “Differential Encoding” on
page 362.
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:
Press Mode > ARB Custom Modulation > Single Carrier Setup > Quick Setup (desired format) >
Modulation Type > Select > More > Define User I/Q > More 1 of 2 > Load Default I/Q Map > QAM > 4QAM.
Data Value
Symbol Table Offset
00
01
10
11
+1
–1
+2
+0
Data = 0011100001
{
{
{
{
{
5th Symbol1st Symbol
3rd Symbol
4th Symbol
2nd Symbol
1st
2nd
3rd
5th
4th
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