Concepts and Features
R&S
®
ZNA
142
User Manual 1178.6462.02 ─ 12
Example: TRL calibration with two and three Lines
If several Lines with different lengths are measured, the analyzer automatically divides
the calibrated range into segments. The calibration data of the longest line is applied to
the lowest segment, the calibration data of the shortest line to the highest segment.
The calibration sweep segments for two Lines with electric lengths l
long
and l
short
(l
long
>
l
short
) are obtained as follows (the Through standard is assumed to be of length l
thr
):
●
The longer Line can be used up to a frequency f
long
where its transmission phase is
equal to 160 deg. This frequency is equal to
f
long
= 4*c
0
/[9*(l
long
– l
thr
)].
●
The shorter Line can be used from a frequency f
short
where its transmission phase
is equal to 20 deg. This frequency is equal to
f
short
= c
0
/[18*(l
short
– l
thr
)].
●
The border between the two frequency segments f
div
is calculated as the geometric
mean of f
long
and f
short
, i.e.
f
div
= sqrt(f
long
* f
short
).
The formulas are also applied if f
long
< f
short
.
For a TRL calibration using three Lines with different length, the allowed frequency
ranges are calculated in an analogous manner to obtain three (ideally overlapping) fre-
quency ranges. The borders between two adjacent frequency ranges are calculated as
the geometric mean of the frequency limits f
long
and f
short
of the two ranges.
A second or third line in the list does not mean that you have to measure two or three
line standards. If the calibrated frequency range is small enough, the calibration is valid
when the analyzer has acquired correction data for a single Line standard. The Match
and Sliding Match standards are not necessary for TRL calibration, however, they must
be measured if TRL is combined with TRM calibration.
Low-frequency extension with TRM
TRL calibration becomes inaccurate if the electrical length difference between Line and
Through standard corresponds to a phase shift below 20°. In practice this means that
TRL is only practicable above a threshold frequency f
TRM
which depends on the lengths
of the longest line and through standards. The threshold frequency is given by:
Calibration
