HP 8753E User Manual page 367

Each standard must be identified as one of five "types": open, short, load, delay/thru, or
arbitrary impedance.
After a standard number is entered, selection of the standard type will present one of five
menus for entering the electrical characteristics (model coefficients) corresponding to that
standard type, such as &&. These menus are tailored to the current type, so that only
characteristics applicable to the standard type can be modified.
The following is a description of the softkeys located within the define standard menu:
. :jX%@ defines the standard type as an open, used for calibrating reflection measurements.
still be added. Pressing this key also brings up a menu for defining the open, including its
capacitance.
As a reflection standard, an open termination offers the advantage of broadband frequency
coverage. At RF and microwave frequencies, however, an open rarely has perfect reflection
characteristics because fringing capacitance effects cause phase shift that varies with
frequency. This can be observed in measuring an open termination after calibration, when
an arc in the lower right circumference of the Smith chart indicates capacitive reactance.
These effects are impossible to eliminate, but the calibration kit models include the open
termination capacitance at all frequencies for compatible calibration kits. The capacitance
model is a cubic polynomial, as a function of frequency, where the polynomial coefficients
are user-deflnable. The capacitance model equation is:
C = (CO) + (Cl x F) + (C2 x F2) + (C3 x P)
where F is the measurement frequency.
The terms in the equation are defined with the specify open menu as follows:
and is scaled by lo-l5 Farads
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are assigned a terminal impedance of 0 ohms, but delay and loss offsets may still be added.
. ~~~~~ defines me sm,-Jxd type w a lo& (te-mjnacon). Lo& are assigned a teeal
impedance equal to the system characteristic impedance ZO, but delay and loss offsets
may still be added. If the load impedance is not ZO, use the arbitrary impedance standard
. . . / . . . . . . . . ; . . / i
calibration, the analyzer will prompt for several load positions, and calculate the ideal load
value from it.
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calibrating transmission measurements.
Application and Operation Concepts