R&S ZNB Series User Manual page 172

®
R&S ZNB/ZNBT
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
l ) are obtained as follows (the Through standard is assumed to be of length l
short
●
The longer Line can be used up to a frequency f
equal to 160 deg. This frequency is equal to
f
●
The shorter Line can be used from a frequency f
is equal to 20 deg. This frequency is equal to
f
●
The border between the two frequency segments f
mean of f
f
The formulas are also applied if f
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
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. How-
ever, 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, TRL is only
practicable above a threshold frequency c
gest electrical length of the used Line standards, and l
Through. The analyzer assumes l
threshold.
User Manual 1173.9163.02 ─ 62
= 4*c /[9*(l – l )].
long 0 long thr
= c /[18*(l – l )].
short 0 short thr
and f , i.e.
long short
= sqrt(f * f ).
div long short
long
short
div
< f .
long short
and f
long short
/[18*(l – l
0 long thr
thr
<< l and uses c /(18*l
thr long 0
Concepts and features
Calibration
and l
long short
where its transmission phase is
where its transmission phase
is calculated as the geometric
of the two ranges.
)], where l denotes the lon-
long
the electrical length of the
) as the frequency
long
(l >
long
):
thr
172