Specify Offset Menu - HP 8753E User Manual

impedance (different from system ZO).
o h m s
.
. $%jJ,lQXG' defmes the load as a sliding load. When such a load is measured during
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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 dehned with offsets in delay, loss, and standard impedance;
assigned minimum or maximum frequencies over which the standard applies, and defined as
(described next).
The ~~~~~ softkey allows you to deiine a distinct label for each standard, so that
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the analyzer can prompt the user with explicit standard labels during calibration (such as
SHORT). The function is similar to delining a display title, except that the label is limited to ten
characters.
After each standard is deiined, including offsets, the ~~~~~~~~~;"~~~.~~ softkey will
terminate the standard deilnition.

Specify Offset Menu

The specify offset menu allows additional specifications for a user-dellned standard. Features
Offsets may be specified with any standard type. This means defining a uniform length of
transmission line to exist between the standard being deilned 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 deiined with
a minhmun and maximum frequency. This is particularly important for a waveguide standard,
since the minimum frequency is used to deilne the waveguide cutoff frequency. Note
several band-limited standards can together be defmed as the same "class" (see specify class
menu). 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 deiined 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
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(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 deilned as though it were a TEM wave (without dispersion).
Application and Operation Concepts
that