A correction file is an ASCII delimited file carrying all the information required to
compensate or embed a given frequency response in the multi-tone, complex
modulation and serial data signals. The file must be composed of a header including a
series of lines with identifiers and parameters, and a list of numerical correction
factors. In lines including more than one item (i.e., one identifier and one parameter),
the items must be separated using commas. Identifiers and parameters are not case
sensitive.
These are the significant fields for the header:
InputBlockSize: It states the number of valid correction factors in the file.
It is a mandatory field.
XStart: It is frequency in Hz corresponding to the first entry in the correction
factor section of the file. It is a mandatory field for serial data and multi-tone
generation in direct mode and optional for multitone in upconverter mode
and complex modulation.
XDelta: It is frequency distance in Hz between consecutive entries in the
correction factor section of the file. It is a mandatory field.
YUnit: Units for the amplitude values in the correction factor section of the
file. Parameter associated to it may be ‘dB’ (for logarithmic relative
amplitudes) or ‘lin’ (for dimensionless linear relative amplitude). This
parameter is optional and its default value is ‘lin’. Phase unit must be always
stated in radians.
The order of the above entries is not relevant. The correction factor section starts with
a line including a single ‘y’ or ‘Y’ character. Entries in this section are made by
Amp1(Fi), Phase1(Fi) pairs. In particular, this format is compatible with adaptive
equalizer files exported in comma-separated value (CSV) format from the Keysight
89600 VSA software package. These files reflect the channel response corrected by
the equalizer so they should be applied through the selection of the
‘Channel_Response’ option in the corresponding ‘CorrectionMode’ drop-down list in
the ‘Corrections’ section of the ‘Multi-Tone’ panel. ‘Complex Modulation” and ‘Serial
Data” panels always expect “frequency response” data so correction will be obtained
by inverting the supplied data. Comments must start with the ‘//’ character sequence
and may use a complete line or be located at the end of any valid line. Empty lines are
also valid.
For signal created from the ‘Serial Data Panel, when correction data is obtained
through an oscilloscope and the Keysight 89600 VSA software, adaptive equalizer
analysis should be applied to a real-only baseband signal (so only one oscilloscope
channel is involved). A direct, bandwidth-limited, straight-forward frequency response
information can be obtained by generating a NRZ signal with sufficient bandwidth and
a convenient edge shape filter that can be handled by the analysis software (i.e. raised
cosine) and setting up the analysis according to the signal characteristics (symbol
rate, filter parameter). NRZ signals can be analyzed through the 89600 VSA software
by selecting “BPSK” as the modulation scheme.
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