5 CALIBRATION AND CALIBRATION KIT
103
In this case the Analyzer program automatically determines the electrical length (delay)
of the two-port device.
In other words, you can perform the calibration without setting the delay of the
UNKNOWN THRU if the frequency increment is small enough. For example, for
UNKNOWN THRU with mml 100
0»and delay coefficient 7.0/1 »
e
, the delay will be
ps477
0»
t
. In this case the frequency increment for automatic defining of the
UNKNOWN THRU delay should be set to MHzF 524
<
D
, or the number of points
within the sweep span of 8 GHz should be no less than 16. To ensure reliable operation,
set the frequency increment and the number of points with double margin at least.
To be able to use the unknown thru calibration algorithm in full two-port calibration, the
calibration kit definition should include the UNKNOWN THRU standard, assigned to
the THRU class for the two ports. The procedure of calibration standards editing and
their assignment to classes is further described in detail.
An UNKNOWN THRU is defined automatically, if you set the delay to zero in the
calibration kit editing menu. Otherwise the user-defined delay value will be used. This
value should be set within the accuracy of 1/4 of the wavelength at the maximum
calibration frequency.
5.1.6.9 TRL Calibration
TRL (Thru-Reflect-Line) calibration is the most accurate calibration method described
herein, as it uses airlines as calibration standards. The TRL calibration requires the use
of the following calibration standards:
§THRU or REFERENCE LINE,
§REFLECT (SHORT or OPEN),
§Second LINE or two MATCHes.
TRL is a general name for a calibration family, which comprises such calibrations as
LRL, TRM, or LRM named depending on the calibration standards used.
If a zero-length THRU is used as the first standard, the method is called TRL
calibration. If a non-zero length LINE is used as the first standard, the calibration
method is called LRL (Line-Reflect-Line). To denote the first standard of the TRL and
LRL calibration, assign TRL-Thru class, which includes THRU and LINEs. A LINE of
TRL-Thru class is also called Reference Line.
An OPEN or SHORT is usually used as a second standard in TRL calibration. To
denote the second standard of the TRL calibration, assign TRL-Reflect class.
A second LINE is used as the third standard in TRL calibration. At low frequencies, at
which MATCHes work well, two MATCHes can be used, as they are an equivalent of a
matched line of infinite length. In the latter case, the calibration method is called TRM
(Thru-Reflect-Match) or LRM (Line-Reflect-Match) respectively. To denote the third
standard of the TRL calibration, assign TRL-line/match class, which includes LINEs
and MATCHes.
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