The bias tee is a diplexer. The low-frequency port is used to set the bias the high-frequency port permits the radio regularity motions but blocks the biasing levels the joint port attaches to the stratagem, which gets both the bias and RF. It is named as tee as the 3 ports are often arranged in the shape of a T.
Primarily used in applications where you need to insert DC currents or voltages into RF circuits. Bias tees are intended to insert DC current into an RF circuit deprived of affecting the RF signal through the core broadcast path. A Bias tee is a three-port device.
The important specifications of bias tees include insertion loss, insertion loss flatness, group delay flatness, and return loss between the high frequency and common ports. Bias tees cover the frequency range from 30kHz to 85GHz, with the insertion loss from 0.5dB to 4.0db. VSWR is from 1.20:1 to 2.00:1