Agilent Technologies E4428C, Руководство пользователя

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186 Chapter 4
Basic Digital Operation
Differential Encoding
Accessing the Differential State Map Table Editor
Press
Configure Differential Encoding
.
This opens the
Differential State Map
table editor, as shown. At this point, you see the data for the
1st symbol (00000000) and the cursor prepared to accept an offset value.You are now prepared to create a
custom differential encoding for the user-defined default 4QAM I/Q modulation. Refer to
Figure 4-37 on
page 186 .
Figure 4-37
Editing the Differential State Map
1. Press
1
>
Enter
.
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.
NOTE
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.
Data
Symbol Table Offset Values Entry Area