HP 8753E manual TRL%RM* Calibration, Why Use TRL Calibration?, TRL lkrminology

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?

nTRL Terminology

nHow TRL*/LRM* Calibration Works

nImproving Raw Source Match and Load Match For TRL*/LRM* Calibration

nThe TRL Calibration Procedure

qRequirements for TRL Standards 0 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