4. Error parameters

4.1 Systematic errors

There are four types of error: directivity, mismatch, frequency response and isolation.

Directivity errors are due to the fact that, when couplers (or bridges) are used in reflection setups, unwanted directivity signals are superimposed on the signal reflected by the device under test, resulting in reflection measurement errors. The more directional the coupler, the smaller the directivity errors. The main cause is non-infinite directivity, defined by the ratio between the isolated (loaded) channel and the coupled channel of the coupler (or bridge) used.

Mismatch errors cover all the various impedance mismatches with respect to the reference impedance (generator, coupler or bridge mismatches, as well as the harmonic...