Short-Open-Load-Through (SOLT) Calibration

SOLT requires short, open, and load calibration standards in the characteristic system (and DUT) impedance. The exact standard values, as determined by their mechanical dimensions, are loaded into the network analyzer prior to calibration. The location where you attach the calibration standards (the network analyzer port, the end of a cable, or inside a test fixture) is where the measurement begins and ends. This location is known as the reference plane or measurement plane.

In addition, you must make an insertable through connection. For instance, you would use a male-to-female cable connection, or another connection that does not require external adapters or devices, to complete the through connection during SOLT calibration. Inserting any component during calibration and not using it in the post calibration measurement results in measurement error. If you cannot make a through connection, the component is referred to as "non-insertable." There are several methods to handle non-insertable devices. The simplest method is to use a set of phase-equal adapters (included in most calibration kits) along with shorts, opens, and loads of each gender. Use one adapter to complete the through connection during calibration and swap it with an appropriate adapter for the DUT connection during post calibration measurements.

Other calibrations in the SOLT family include the response calibration. It is quick, but no more accurate than removing the path loss across frequency. It only accounts for the forward and reverse tracking terms in the 12-term error model. You can perform a one-port calibration by placing a short, open, and load on port one during calibration. This step saves some time if you require only a one-port measurement, such as when measuring the return loss of an antenna. An enhanced one-port calibration performs a full one-port calibration and uses the through connection to measure port two. This configuration is common in a T/R architecture, in which no source is present on port two. Finally, there is full two-port SOLT calibration, in which you place shorts, opens, and loads on both ports, as directed by the calibration routine. The full two-port calibration concludes with the through connection.