Keysight Technologies X-Series, Programming Manual

Page: 331 / 398

Keysight CXG, EXG, and MXG X-Series Signal Generators Programming Guide 331
Creating and Downloading User–Data Files
User File Data (Bit/Binary) Downloads
Binary File Type Data
With the Binary file type, the signal generator sees all of the bytes within the
downloaded file and attempts to use all of the data bits. When using this file
type, the biggest challenge is creating the data so that the signal generator
uses all of the bits (bytes) contained within the file. This is referred to as using
an even number of bytes. The method of creating the user file data pattern
depends on whether you are using unframed or framed data. The following two
sections illustrate the complexities of using the binary file format. You can
eliminate these complexities by using the bit file format (see “Bit File Type
Data” on page 328 ).
Unframed Binary Data
When creating unframed data, you must think in terms of bits per symbol; so
that your data pattern begins and ends on the symbol boundary, with an even
number of bytes. For example, to use 16QAM modulation, the user file needs to
contain 32 bytes:
— enough data to fill 16 states 4 times
— end on a symbol boundary
— create 64 symbols (the signal generator requires a minimum of 60 symbols
for unframed data)
To do the same with 32QAM, requires a user file with 40 bytes.
When you do
not use an even number of bytes, the signal generator repeats
the data in the same symbol where the data stream ends. This means that your
data would not end on the symbol boundary, but during a symbol. This makes
it harder to identify the data content of a symbol. The following figure
illustrates the use of an uneven number of bytes and an even number of bytes.
16QAM 4 bits/symbol:
1 0 1 1 0 1 1 0 1 1 0 0 1 1 0 0
Symbol Symbol Symbol Symbol
1 0 1 1 0 1 1 0 1 1 0 0 1 1 0 0 1 0 1 1 0 1 1 0 1 1 0 0 1 1 0 0 1 0 1
Symbol
Symbol Symbol Symbol Symbol Symbol Symbol
Data repeats during a symbol
1 0 1 1 0 1 1 0 1 1 0 0 1 1 0 0
Symbol Symbol Symbol Symbol
Data repeats at the symbol boundary
Unframed Data
32QAM 5 bits/symbol:
Even Number of Bytes
Uneven Number of Bytes
1 0 1 1 0 1 1 0 1 1 0 0 1 1 0 0
Data pattern:
Data
repeats
Using an uneven number of bytes makes it harder to identify the data within a symbol.
MSB LSB