ViaSat MEOLink User Manual page 25

MEOLink User Manual
2.1.5.3 Filter File Formats
2.1.5.4 Configuring Custom Filters
To select and use the custom filter files, open the MEOLink Modem Web Interface and
navigate to the Modem category on the Configuration page. Select which custom file to use
Rev 002vx
1141780,
2. Complete the load by logging into the MEOLink modem Operator Main Menu,
see section 2.1.2, and:
c. From the User Menu, enter y to copy custom filter files from the TFTP
server to the internal flash drive; see Figure 17.
Figure 17: Filter Update via TFTP (y command)
There are 3 custom filter files, customFilter020.txt, customFilter025.txt,
customFilter035.txt that represent the 0.20, 0.25, and 0.35 roll‐off of the square‐root
raised cosine transmit data shaping filters, respectively.
The file format for the custom filters containing waveform pre‐distortion coefficients is:

16384 lines, where each line is a 32‐bit value represented in HEX format (no leading
0x), e.g. the first 12 lines might look like this:
FFE50000
FFE50000
FFE50000
FFE50000
FFE50000
FFE60000
FFE60000
FFE60000
FFE60000
FFE60000
FFE70000
FFE70000

Each 32‐bit value represents a filter coefficient as a real and imaginary pair. The 16
most significant bits represent the "I" or real part in 2's complement and the 16
least significant bits represent the "Q" or imaginary part in 2's complement.
2‐17