R&S FSV-K70, Руководство пользователя

Страница: 27 / 394

Brief Description of Vector Signal Analysis
R&S
®
FSV-K70
27 Operating Manual 1176.7578.02 ─ 09
2.3.3 Differential PSK
With differential PSK, the information is represented in the phase shift between two
consecutive decision points. The absolute position of the complex sample value at the
decision point does not carry information.
In the physical constellation diagram, the constellation points at the symbol decision
points obtained after ISI-free demodulation are shown (as with common PSK meth-
ods). This diagram corresponds to the display on the analyzer. The position of the con-
stellation points is standard-specific. For example, some QPSK standards define the
constellation points on the diagonals, while other standards define the coordinate axes.
In Table 2-5 , the symbols are assigned to phase shifts. The QPSK (INMARSAT) map-
ping corresponds to simple QPSK with phase-differential coding.
Tables Table 2-6 and Table 2-7 show two types of differential 8PSK modulation.
Another type of differential PSK modulation is shown in Table 2-6 .
Differential coding according to VDL is shown in Table 2-8 . It can be used for modula-
tion types with 3 bits/symbol, e.g. 8PSK.
Other types of modulation using differential coding method are described in Chap-
ter 2.3.4, "Rotating Differential PSK Modulation" , on page 28.
Figure 2-19: Constellation diagram for DQPSK (INMARSAT and NATURAL) including the symbol
mapping
Table 2-5: DQPSK (INMARSAT)
Logical symbol mapping
Modulation symbol (binary indication: MSB, LSB) 00 01 10 11
Phase shift 0° -90° +90° 180°
Symbol Mapping