Configuring the Internal Baseband Source
R&S
®
SMBV100B
141User Manual 1178.4460.02 ─ 03
Table 3-8: Common coding algorithms
Coding Coding algorithm Applicable for
K bit/symbol
Required option
"None" b
n
= a
n
k = 1...8 -
"Differential"
b
n
= (a
n
+ b
–1
) modulo 2
k
k = 1...7
"Differential + Gray" Gray coding with additional differential coding k = 1...7
"GSM" d
n
= NOT (d
n
EXOR d
–1
) k = 1 R&S SMBVB-B10
"Phase differential
coding"
1)
R&S SMBVB-B10
1)
"Phase differential coding" INMARSAT and PHASE DIFF correspond to system
standards Inmarsat-M and DVB according to ETS 300 429. The INMARSAT coding
can generally be used for modulation types with 2 bits/symbol, such as QPSK.
Examples
The following examples illustrate how some of the different common coding schemes
combined with a modulation method influence the signal.
Example: Differential coding for QPSK modulation with K = 2 bit/symbol
Decimal display; the value range for modulation symbols is a
n
= {0, 1, 2, 3}
According to Table 3-8 and for k = 2, the recursive coding is defined as b
n
= (a
n
+ b
–1
)
modulo 4
Depending on the state of a preceding modulation symbol b
–1
, the coded modulation
symbol b
n
is obtained, for example, from modulation symbol a
n
= 2 as follows:
b
–1
0 1 2 3
b
n
2 3 0 1
With differential coding, the assignment of modulation symbols a
n
(binary indication:
MSB, LSB) to the phase differences shown in the following table is generated:
Table 3-9: Phase difference for QPSK
Modulation symbol a
n
00 01 10 11
Phase difference 0° 90° 180° 270°
Generating Custom Digital Modulated Signals
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