S-Parameters; Understanding S-Parameters; S-Parameters Of A Two-Port Device - Agilent Technologies 8719D User Manual

S-Parameters

The m key provides access to the S-parameter menu which contains softkeys that can be
used to select the parameters or inputs that define the type of measurement being performed.

Understanding S-Parameters

S-parameters (scattering parameters) are a convention used to characterize the way a device
modifies signal flow. A brief explanation of the S-parameters of a two-port device is provided
here. For additional details, refer to Hewlett-Packard Application Notes A/N 95-l and A/N 154.
S-parameters are always a ratio of two complex (magnitude and phase) quantities. S-parameter
notation identifies these quantities using the numbering convention:
s out in
where the first number (out) refers to the test-device port where the signal is emerging and
the second number (in) is the test-device port where the signal is incident. For example, the
S-parameter %I identifies the measurement as the complex ratio of the signal emerging at the
test device's port 2 to the signal incident at the test device's port 1.
Figure 6-9 is a representation of the S-parameters of a two-port device, together with an
equivalent flowgraph. In the illustration, "a" represents the signal entering the device and "b"
represents the signal emerging. Note that a and b are not related to the A and B input ports on
the analyzer.
Application and Operation Conceptc
Figure 6-9. S-Parameters of a Two-Port Device