5 CALIBRATION AND CALIBRATION KIT
105
or more TRL LINEs are used to extend the calibration frequency. For example, in case
of using two TRL LINEs the frequency range can be increased up to 1:64.
TRL MATCH
Unlike TRL/LRL calibration, TRM/LRM calibration uses MATCHes, which are the
equivalent to the infinitely long LINE, instead of a TRL LINE. Theoretically
TRM/LRM calibration has no frequency limitations. However, the use of TRM/LRM
calibration at higher frequencies is limited by the quality of the MATCHes. As a rule,
the TRM/LRM calibration is used at lower frequencies, as it is good starting from zero
frequency.
TRL REFLECT
There are no strict requirements to the TRL REFLECT standard. You should know only
approximate parameters of the TRL REFLECT standard. The REFLECT standard
should have high reflection coefficient, close to 1. The phase of the standard must be
known within ±90°. Normally, any OPEN or SHORT meets this requirement. The next
requirement is that the reflection coefficient must be the same for all the ports. If one
standard is used for all the ports by turns, then this requirement is automatically
fulfilled. If the ports have different genderes or types of connectors, use special
standards with the identical electrical specifications, which are available in pairs.
TRL Calibration Frequency Extension
To extend the frequency of TRL calibration a method of dividing into several non-
overlapping bands is applied. For each frequency band a separate TRL LINE of
different length is used. The phase difference between each TRL LINE and the
REFERENCE LINE must be from 20° to 160°, as indicated above. A MATCH standard
is used in the lowest frequency band.
The Analyzer software allows using up to 8 LINES for calibration frequency extension.
To achieve this, there are two steps of handling the calibration kits:
- defining frequency limits to calibration standards (see section 5.3.2);
- assigning classes to calibration standards, where up to 8 calibration standards can be
assigned to one class (see section 5.3.4).
Perform the above mentioned dividing of the calibration band into sub-bands and assign
a separate TRL LINE to each of them in the calibration kit editing menu before
calibration.
5.1.6.10 Multiline TRL Calibration
Regular TRL calibration, described in the previous section uses several LINEs of
different lengths for frequency extension. It is provided by the method of dividing the
frequency band into separate sub-bands.
Multiline TRL calibration also uses several LINEs. But it does not divide the frequency
band into several sub-bands. Instead, all the LINEs are used simultaneously over the
whole calibration bandwidth. The redundancy of the LINEs measurements allows for
both extending the frequency range and increasing the calibration accuracy. The number
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