AN3009 Datasheet, PDF (1/2 Pages) M/A-COM Technology Solutions, Inc. – S-Parameter S2P File Format

Application Note
AN3009
S-Parameter S2P File Format
Introduction
Listed among many of M/A-COM’s products are files
that describe the small signal scattering matrix, or s-
parameters, of the device. The S2P format is an
industry standard and thus is recognized by many
simulation programs. This application note de-
scribes the basic file format. The general case of
the touchstone standard, not described in this appli-
cation note, extends to more than two ports. Touch-
stone is a registered trademark of Agilent corpora-
tion and is used with permission.
File Format Description
S2P files are ASCII text files. As such, they can be
viewed or edited by any standard text editor. The
files are not case sensitive.
Option Line
Each file generally has an option line that resembles
the following.
# GHZ S MA R 50
In the event that no option line is shown, the values
shown above are the defaults.
The ‘#’ defines the line as an option line.
‘GHZ’ defines the units of frequency used in the
data. GHZ, MHZ, KHZ, and HZ are acceptable val-
ues.
‘S’ is the type of parameter that has been measured.
Typically, this is the type of data the M/A-COM pro-
vides. Other possibilities include Y, Z, H, and G
which are well documented in many circuit analysis
textbooks.
‘MA’ is what format that the complex data is in.
DB: Decibel Magnitude/Degree Angle
MA: Linear Magnitude/Degree Angle (polar form)
RI: Real Part/Imaginary Part (rectangular form)
The ‘DB’ form decibel magnitude is computed as
20*Log(linear magnitude).
‘R 50’ define the system impedance at which the
measurements were taken. For CATV systems this
impedance will be 75 ohms. Normalized measure-
ments will have a value of 1 ohm.
Comment Lines
Rev. V2
Comment lines are denoted by a ‘!’ preceding the
text.
! This is a comment line
Comment lines are used optionally for description
and test conditions.
Data
The data consists of 9 columns. The first column is
always frequency with the units defined in the option
line. The next 8 columns define the two port
parameters for that given frequency. The order of
these parameters are:
<FREQ> <X11> <X11> <X21> <X21> <X12> <X12>
<X22> <X22>
Where X can be S, Z, Y, H, or G as defined in the
option line. The real or magnitude of the parameter
is listed first (denoted by the boldface), followed
immediately by the imaginary or phase (denoted by
the italicized). Phase angles are always measured
in degrees. These formats are also defined in the
option line.
S1P files describe a single reflection impedance.
There are only three columns denoted by
FREQ X11 X11
Noise Parameters
Noise parameters describe the noise circles of a
device. They are optionally included at the end of
an S2P file. There is not a separate option line for
noise parameters. The first frequency of the noise
parameters must be less than the highest frequency
of the two port parameters so the simulators can
distinguish where the two port data stops and the
noise data begins.
There are five columns that describe noise
parameters. The following describes the noise
parameter data format.
<FREQ> <NF> <|G|> <ÐG> <Rn>
1
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