Agilent Technologies E8257C PSG, E8267C PSG, E8247C PSG CW manual How Differential Encoding Works

Custom Real Time I/Q Baseband

Working with Differential Data Encoding

How Differential Encoding Works

Differential encoding employs offsets in the symbol table to encode user-defined modulation schemes. The Differential State Map editor is used to introduce symbol table offset values, which in turn cause transitions through the I/Q State Map based on their associated data value. Whenever a data value is modulated, the offset value stored in the Differential State Map is used to encode the data by transitioning through the I/Q State Map in a direction and distance defined by the symbol table offset value.

Entering a value of +1 causes a 1-state forward transition through the I/Q State Map. As an example, consider the following data/symbol table offset values. These symbol table offsets result in one of the transitions shown.

NOTE		The following I/Q State Map illustrations show all possible state transitions using a
		particular symbol table offset value. The actual state-to-state transition depends on the state
		in which the modulation starts.
				Example 1	Example 2
	Example	Data	Offset
				transition 1 state forward	transition 1 state backward
			Value
	1	00000000	+1
	2	00000001	−1
	3	00000010	+2
	4	00000011	0

Example 3	Example 4
transition 2 states forward	no transition

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