As with most spectrum analyzers, a microwave preselector is employed above 3 GHz. An RF preselector can adversely affect the frequency response and phase linearity in the preselector pass band. To avoid this problem, Agilent offers a switched microwave preselector bypass Option 123. For better amplitude and phase measurements above 3 GHz, Option 123 is highly recommended.
By avoiding the preselector, measurements can be made with far less amplitude variability, thus greatly increasing repeatability. Passband ripple in amplitude and phase is reduced when not using the preselector.
Option 123 is highly recommended for use with the 40/80 MHz bandwidth digitizers (Options 140/122), available on the 6.7 GHz, 13.2 GHz, and 26.5 GHz PSA models.
Option 123 is also available on the 42.98 GHz, 44 GHz, and 50 GHz. It is mandated for the 40/80 MHz bandwidth digitizer (Options 122/140), available on 44 GHz and 50 GHz PSA models.
Option 123 upgrades are available for existing PSA instruments with serial number prefixes being equal to or greater than US4430 or MY4430.