how does bias tee work in regard to amplifier testing

Hello!

A bias tee enables you to add a DC voltage (supply voltage) on top of the RF. Additionally a capacitor is included to keep the measuring sender (or receiver) free of that DC offset.

So the bias tee has a low pass filter between the DC voltage input and the DUT port, and a high pass filter between the DUT port and the receiver/sender port.

Please have a look at this picture:

http://www.ird-inc.com/image/bt-250.jpg

CU