Instrument Function
R&S
®
SMBV100A
344
Operating Manual 1176.8016.02 ─ 17
however assigned to the individual modulation symbols. The following tables show the
assignment of modulation symbols to phase shifts of the I/Q vector in relation to the
selected coding.
Table 5-4: Phase shifts for pi/4DQPSK
Modulation symbol a
n
(binary indication: MSB, LSB)
00
01
10
11
Phase shifts without coding
+ 45°
+ 135°
- 135°
- 45°
Phase shifts with coding NADC, PDC, PHS,
TETRA or APCO25 (PSK)
+ 45°
+ 135°
- 45°
- 135°
Phase shifts with coding TFTS
- 135°
+ 135°
- 45°
+ 45°
Coding algorithms
Common coding types are listed in the following table.
Table 5-5: Coding algorithms
Coding
Coding algorithm
Applicable for K bit/symbol
NONE
b
n
= a
n
k = 1...8
Differential
b
n
= (a
n
+ b
n-1
) modulo 2
k
k = 1...7
Differ Gray
Gray coding with additional differ-
ential coding
k = 1...7
GSM
dc
n
= not (d
n
exor d
n-1
)
k = 1
Example: Differential coding for QPSK modulation with K = 2 bit/symbol
Decimal display; value range for modulation symbols
Recursive coding is defined as follows: b
n
= (a
n
+ b
n-1
) modulo 4
Depending on the state of a preceding modulation symbol b
n-1
the coded modulation
symbol b
n
is obtained for example from modulation symbol a
n
= 2 as follows:
a
n
= 2
b
n-1
b
n
0
2
1
3
Baseband Signal - Baseband Block
