HP 8753E manual Application and Operation Concepts

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: “‘... (’ ,,,: y

. :jX%@ defines the standard type as an open, used for calibrating reflection measurements. TT ,,...:.,,i:.i

Opens are assigned a terminal impedance of infinite ohms, but delay and loss offsets may 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:

..:. :

%J& allows you to enter the CO term, which is the constant term of the cubic polynomial

and is scaled by lo-l5 Farads

..iiii.l i:

?$&: allows you to enter the Cl term, expressed in F/Hz (Farads/Hz) and scaled by 10V2’.

;#$ allows you to enter the C2 term, expressed in F/Hz2 and scaled by 10-36.

&: allows you to enter the C3 term, expressed in F/H23 and scaled by 10-45.

/.........;..; i....,.,..%.... F., /

n ###$I@ defines the standard type as a short, for calibrating reflection measurements Shorts

.A....,,..:,.:::.../ ,....,./.s..s ...A.....

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

deiinition.

... /........;../i

;J@&f& defies the lo& u a jjxed (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.

n~~~~~~ deilnes the standard type as a transmission line of specified length, for calibrating transmission measurements.

6-66 Application and Operation Concepts