HP 8753E manual Understanding S-Parameters

S-Parameters

The (Meas) 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 Sparameter & 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 6-8 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.

INCIDENT 521

TRANSMITTED	INCIDENT
S12	( R E V E R S E )

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Figure 6-S.S-Parameters of a Two-Port Device

Application and Operation Concepts 6-26