7- 61
Operating Concepts
Modifying Calibration Kits
— allows you to specify the (arbitrary) impedance of the standard, in
ohms.
— defines the load as a fixed (not sliding) load.
— defines the load as a sliding load. When such a load is measured during calibration, the
analyzer will prompt for several load positions, and calculate the ideal load value from it. Normally,
arbitrary impedance standards are fixed rather than sliding.
Any standard type can be further defined with offsets in delay, loss, and standard impedance; assigned
minimum or maximum frequencies over which the standard applies, and defined as coax or waveguide. The
softkey accesses the specify offset menu (described next).
The softkey allows you to define a distinct label for each standard, so that the analyzer can
prompt you with explicit standard labels during calibration (such as SHORT). The function is similar to
defining a display title, except that the label is limited to ten characters.
After each standard is defined, including offsets, the softkey will terminate
the standard definition.
Specify Offset Menu
The specify offset menu allows additional specifications for a user-defined standard. Features specified in
this menu are common to all five types of standards.
Offsets may be specified with any standard type. This means defining a uniform length of transmission line
to exist between the standard being defined and the actual measurement plane. (Example: a waveguide
short circuit terminator, offset by a short length of waveguide.) For reflection standards, the offset is
assumed to be between the measurement plane and the terminating element of the standard (one-way
only). For transmission standards, the offset is assumed to exist between the two reference planes (in
effect, the offset is the thru). For both reflection and transmission, the offset is entered as a one-way offset.
Three characteristics of the offset can be defined: its delay (length), loss, and impedance.
In addition, the frequency range over which a particular standard is valid can be defined with a minimum and
maximum frequency. This is particularly important for a waveguide standard, since the minimum frequency
is used to define the waveguide cutoff frequency. Note that several band-limited standards can together be
defined as the same "class" (see
“Specify Class Menu” on page 7-62). Then, if a measurement calibration is
performed over a frequency range exceeding a single standard, additional standards can be used for each
portion of the range.
Lastly, the standard must be defined as either coaxial or waveguide. If it is waveguide, dispersion effects are
calculated automatically and included in the standard model.
The following is a description of the softkeys located within the specify offset menu:
• allows you to specify the one-way electrical delay from the measurement
(reference) plane to the standard, in seconds (s). (In a transmission standard, offset delay is the delay
from plane to plane.) Delay can be calculated from the precise physical length of the offset, the
permittivity constant of the medium, and the speed of light.
In coax, group delay is considered constant. In waveguide, however, group delay is dispersive, that is, it
changes significantly as a function of frequency. Hence, for a waveguide standard, offset delay must be
defined as though it were a TEM wave (without dispersion).
• allows you to specify energy loss, due to skin effect, along a one-way length of coax
offset. The value of loss is entered as ohms/nanosecond (or Giga ohms/second) at 1 GHz. (Such losses
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