Bias Tees

Bias tees allow the insertion of direct current (DC) voltages into a signal path without disrupting the existing signal in that path. They are used to supply an active device like an amplifier, laser diode, photodiode, or optical modulator with a bias current or bias voltage while allowing high speed, radio frequency (RF) signals to pass through with minimum signal degradation. Bias tees are typically small boxes with two coaxial connectors, and a connector to accept DC voltage from a power supply. Using a bias device allows the provision of power through RF connections. By avoiding connections, a bias tee can help weatherproof remote preamplifiers. A magic tee is a bias tee that provides a very good isolation (> 30 dB isolation) between its co-linear ports and only 3 dB loss from the co-linear to the E and H ports.