Part of THRU measurements can be omitted in the full three/four-port SOLT or TRL calibration. Since the calibration coefficients are calculated while omitting part of the THRU measurement data, the effect of errors when acquiring calibration data becomes larger than in the normal full three/four-port calibration.
In the simplified three-port calibration, one out of three measurements of THRU is omitted. Any of the measurements can be omitted. For example, if the port numbers of a three-port calibration are 1-2-3, 1-2 or 1-3 or 2-3 measurements can be omitted.
In the simplified four-port calibration, up to three out of six measurements of THRU are omitted. However, if the topology is other than star (with one common port), it is recommended to perform a fourth measurement to enhance the calibration accuracy.
Example 1
Three out of six THRU measurements have been performed, the topology of THRU connection is star, for example 1-2, 1-3, 1-4. The simplified calibration can be finished.
Example 2
Three out of six THRU measurements have been performed, the topology of THRU connection is not star, for example 1-2, 2-3, 3-4. The simplified calibration can be finished, however to enhance accuracy it is recommended to perform one more (any) THRU measurement.
note |
Unlike in the calibration using full set of calibration standards, in the simplified calibration the quality of measurements is more critical. Observe the following instructions: •Use calibration standards with good stability and repeatability. •Make sure the standard model is defined correctly: do not omit the THRU definition if it is not a zero-length THRU (not flush THRU). •Use quality cables with small phase/amplitude change on bends. •Use precision connectors. |
