Configuring the Internal Baseband Source
R&S
®
SMBV100B
142User Manual 1178.4460.02 ─ 03
Example: Differential coding for modulation type pi/4DQPSK
With differential coding switched on at the same time, the obtained constellation dia-
gram for pi/4DQPSK is similar to that of 8PSK. Phase shifts are however assigned to
the individual modulation symbols. The Table 3-10 shows the assignment of modula-
tion symbols a
n
(binary indication: MSB, LSB) to phase shifts of the I/Q vector in rela-
tion to the selected coding.
Table 3-10: Phase shifts for pi/4DQPSK
Modulation symbol a
n
00 01 10 11
"Coding = OFF" + 45° + 135° - 135° - 45°
"Coding = NADC, PDC, PHS, TETRA, or APCO25
(PSK)"
+ 45° + 135° - 45° - 135°
"Coding = TFTS" - 135° + 135° - 45° + 45°
Example: Gray and differential coding for 8PSK modulation
When this coding scheme is used, the gray coding according to the gray code is per-
formed before the differential coding. The later uses the recursive coding algorithm
quoted above (see Table 3-8). The assignment of modulation symbols a
n
(binary indi-
cation: MSB, LSB) to the phase differences shown in the following table is generated:
Table 3-11: Differential coding according to VDL
1)
Modulation symbol d
n
000 001 010 011 100 101 110 111
Phase difference 0° 45° 135° 90° 270° 315° 225° 180°
1)
"Differential coding according to VDL" can be used for modulation types with 3 bits/
symbol, e.g. 8PSK.
3.5.5.2 Predefined Baseband Filters
The Table 3-12 shows the filters that are available, together with their associated
parameters. The filter characteristic is displayed in graphical form.
Filter names Cosine and Root Cosine
The filter names "Cosine" and "Root Cosine" are used for backwards compatibility with
former Rohde & Schwarz signal generators.
These names do not correspond to the underlying transfer functions the filters use:
●
"Cosine" filters use raised cosine transfer function.
●
"Root Cosine" filters use root raised cosine (RRC) transfer function.
Generating Custom Digital Modulated Signals
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