role of attenuator in scalar network analisers

A scalar network analyzer consists of a signal generator and a calibrated detector.
Detector operates as calibrated if the input power falls within specified limits. Attenuator is used to make sure it does.
Also, the system is used to evaluate gain/loss of DUTs. To calibrate, attenuator is inserted as a DUT.

Attenuators can also be used to to improve return loss and avoid multiple reflections.

For vector network analyzers, we use calibration with TRL/SOLT to improve the return loss. These methods are not available for scalar network analyzers.