6-28 ES User’s Guide
Calibrating for Increased Measurement Accuracy
Calibration Kits
C
0
, C
1
, C
2
, C
3
At high frequencies, an open rarely has perfect
reflection characteristics because fringing capacitance
causes phase shift that varies with frequency.
These effects are impossible to eliminate, but the
calculation built into the analyzer includes an
open-circuit capacitance model. This capacitance model
is a third-order polynomial as a function of frequency,
where the polynomial coefficients are user-definable.
The capacitance model equation is: C(f) = (C
0
) + (C
1
*f)
+ (C
2
*f
2
) + (C
3
*f
3
) where f is the measurement
frequency.
The terms in the equation are defined when specifying
the open as follows:
•C
0
is used to enter the C
0
term, which is the
constant term of the third-order polynomial and is
expressed in Farads.
•C
1
is used to enter the C
1
term, expressed in F/Hz
(Farads/Hz).
•C
2
is used to enter the C
2
term, expressed in F/Hz
2
.
•C
3
is used to enter the C
3
term, expressed in F/Hz
3
.
For further information on calibration kits and determining standard
characteristics, refer to HP Product Note 8510-5A (HP Publication
No. 5956-4352). To view this product note on the Web, go to
http://www.tmo.hp.com and select “Application Note Library.”
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