Agilent Technologies MXG (Series A and B) Guía de usuario descargar pdf (Pagina 304)

290 Agilent N5161A/62A/81A/82A/83A MXG Signal Generators User’s Guide

Custom Digital Modulation (Option 431)

Differential Encoding

The following illustration shows a 4QAM modulation I/Q State Map.

Differential encoding employs relative offsets between the states in the symbol table to encode

user–defined modulation schemes. The Differential State Map table 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 will cause a 1–state forward transition through the I/Q State Map, as shown

in the following illustration.

NOTE The following I/Q State Map illustrations show all of the possible state transitions using a

particular symbol table offset value. The actual state–to–state transition would depend upon

the state in which the modulation had started.

As an example, consider the following data/symbol table offset values.

Table 11-2

Data Offset Value

00000000 +1

00000001 –1

1st Symbol

Distinct values: +1, +1

Data = 00000000

2nd Symbol

Distinct values: –1, +1

Data = 00000001

4th Symbol

Distinct values: +1, –1

Data = 00000011

3rd Symbol

Distinct values: –1, –1

Data = 00000010

1 2 ... 299 300 301 302 303 304 305 306 307 308 309 ... 361 362

Sin comentarios

Agilent Technologies MXG (Series A and B) Guía de usuario Pagina 304