Trl/Lrm Calibration; Why Use Trl Calibration - Agilent Technologies 8719D User Manual

The HP 8719D/20D/22D RF network analyzer has the capability of making calibrations using
the "TRL" (thru-reflect-line) method. This section contains information on the following
subjects:

Why Use TRL Calibration?

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TRL l&minology
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How TRL*/LRM* Calibration Works
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How True TRL/LRM Works (Option 400 Only)
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Improving Raw Source Match and Load Match For TRL*/LRM* Calibration
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The TRL Calibration Procedure
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Requirements for TRL Standards
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Why Use TEL Calibration?
This method is convenient in that calibration standards can be fabricated for a specific
measurement environment, such as a transistor test fixture or microstrip. Microstrip devices
in the form of chips, MMIC's, packaged transistors, or beam-lead diodes cannot be connected
directly to the coaxial ports of the analyzer. The device under test (DUT) must be physically
connected to the network analyzer by some kind of transition network or fixture. Calibration
for a iixtured measurement in microstrip presents additional difficulties,
A calibration at the coaxial ports of the network analyzer removes the effects of the network
analyzer and any cables or adapters before the fixture; however, the effects of the fixture itself
are not accounted for. An in-fixture calibration is preferable, but high-quality Short-Open-Load-
Thru (SOIT) standards are not readily available to allow a conventional Full 2-port calibration
of the system at the desired measurement plane of the device. In microstrip, a short circuit is
inductive, an open circuit radiates energy, and a high-quality purely resistive load is diflicult to
produce over a broad frequency range. The Thru-Reflect-Line (TRL) 2-port calibration is an
alternative to the traditional SOI.2' Full 2-port calibration technique that utilizes simpler, more
convenient standards for device measurements in the microstrip environment.
For coaxial, waveguide and other environments where high-quality impedance standards are
readily available, the traditional short, open, load, thru (SOUP) method provides the most
accurate results since all of the significant systematic errors are reduced. This method is
implemented in the form of the S11 l-port, s22 l-port, and full 2-port calibration selections.
In alI measurement environments, the user must provide calibration standards for the desired
calibration to be performed. The advantage of TRL is that only three standards need to
be characterized as opposed to 4 in the traditional open, short, load, and thru full 2-port
calibrations Further, the requirements for characterizing the T, R, and L standards are less
stringent and these standards are more easily fabricated.
Application and Operation Concepte