Instrument Function
R&S
®
SMU200A
328Operating Manual 1007.9845.32 ─ 15
5.8.2.1 Internal PRBS Data and Data Patterns
PRBS generators deliver pseudo-random binary sequences of differing length and dura-
tion. They are known as maximum length sequences, and are generated with the aid of
ring shift registers with feedback points determined by the polynomial.
By way of example, the diagram below shows a 9-bit generator with feedback to registers
4 and 0 (output).
Fig. 5-26: 9-bit PRBS generator
For PRBS15 and PRBS23, a CCITT V.52-compliant data inversion is performed in the
feedback path automatically as shown below:
The pseudo-random sequence from a PRBS generator is uniquely defined by the register
number and the feedback. The following table describes all the available PRBS genera-
tors:
Table 5-4: PRBS generators
PRBS generator Length in bits Feedback to Menu selection
9-bit 29 -1 = 511 Registers 4, 0 PRBS 9
11-bit 211 -1 = 2047 Registers 2, 0 PRBS 11
16-bit 216 -1 = 65535 Registers 5, 3, 2, 0 PRBS 16
20-bit 220 -1 = 1048575 Registers 3, 0 PRBS 20
21-bit 221 -1 = 2097151 Registers 2, 0 PRBS 21
The "Data Source" selection for PRBS data from the menus is "PN11, ...".
Simple data patterns such as binary 0 strings or 1 strings can also be used as internal
modulation data. The "Data Source" selection from the menus is "ALL 0", "ALL1". A var-
iable bit string with a maximum length of 64 bits can be entered in an input field by
selecting "Pattern."
5.8.2.2 Internal Modulation Data from Lists
Internal modulation data can be generated and stored in the form of binary lists. A sep-
arate file is created for each list and held on the instrument's hard disk.
Baseband Signal - Baseband Block
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