Rohde & Schwarz SMIQ02B - Internal PRBS Data and Pattern; Table 2-11 PRBS Generators of Modulation Coder

Digital Modulation SMIQ
1125.5555.03 E-92.94
2.10.3 Internal PRBS Data and Pattern
The PRBS generators in the modulation coder provide pseudo random binary sequences (PRBS) of
different length and period. They are called sequences of maximum length and are generated by means
of feedback shift registers.
The following schematic shows the 9-bit generator with feedback from registers 4 and 0 (output).
8
765 4 3
2
10
SER DAT
A
EXOR
Fig. 2-53 9-bit PRBS generator
The pseudo random sequence of a PRBS generator is determined by the number of registers and the
feedback. The following table describes all available PRBS generators:
Table 2-11 PRBS generators of modulation coder
PRBS generator Length in bit Feedback to
9 Bit 2
9
-1 = 511 Register 4, 0
15 Bit 2
15
-1 = 32767 Register 1, 0
16 Bit 2
16
-1 = 65535 Register 5, 3, 2, 0
20 Bit 2
20
-1 = 1048575 Register 3, 0
21 Bit 2
21
-1 = 2097151 Register 2, 0
23 Bit 2
23
-1 = 8388607 Register 5, 0
PRBS data as a source for modulation data are selected in the menu via SOURCE - SOURCE PRBS.
The period is determined by PRBS LENGTH.
Other internal modulation data are available as simple data patterns such as 0s or 1s. Selection is via
SOURCE - SOURCE PATTERN.
Note: With PRBS data or Pattern selected as source for modulation data, only external control
signals can be used. A combination with control signals from lists is not possible.