Keysight Technologies N5221A, Service Manual, Page: 144 / 368

5-20 Keysight N5221A/22A Service Guide
Theory of Operation
Signal Separation Group Operation
5-
A34–A37 65-dB Source Step Attenuators and A38–A41 Bias Tees
On 4-port models with some options, a step attenuator and a bias tee are
placed in the signal path of each test port between the A25–A28 receiver
couplers and the A29–A32 test port couplers.
On 2-port models with some options, a step attenuator and a bias tee are
placed in the signal path of each test port between the A25 and A28 receiver
couplers and the A29 and A32 test port couplers.
The 65-dB step attenuators provide coarse power control for the test port
signals. They are electro-mechanical step attenuators that provide 0 to 65 dB
of attenuation in 5-dB steps. They adjust the power level to the DUT without
changing the level of the incident power in the reference path. These
attenuators are controlled by the A17 CPU board.
The bias tees are to provide DC biasing for the DUT.