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TRL%RM*
Calibration
The HP 8753E RF network analyzer has the capability of making calibrations using the “TRL”
(thru-reflect-line) method. This section contains information on the following subjects:
w
Why Use TRL Calibration?
n
TRL Terminology
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How
TRL*/LRM*
Calibration Works
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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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TRL Options
Why Use
TRL
Calibration?
This method is convenient in that calibration standards can be fabricated for a specific
measurement environment, such as a transistor test
iixture 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 iixture. Calibration
for a
ilxtured
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-iixture
calibration is preferable, but high-quality
Short-Open-Load-
Thru
@OKI‘)
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 difficult to
produce over a broad frequency range. The Thru-Reflect-Line (TRL)
2-port
calibration is an
alternative to the traditional
SOIX
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
(SOLI”)
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,
s2
l-port, and full
2-port
calibration selections
In all 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.
TRL
lkrminology
Notice that the letters TRL, LRL,
LRM,
etc are often interchanged, depending on the
standards used. For example,
“LRL”
indicates that two lines and a reflect standard are used;
“TRM”
indicates that a thru, reflection and match standards are used. All of these refer to the
same basic method.
6-92 Application and Operation Concepts