BD211B is a bidirectional detector intended for simultaneous sampling of incident and reflected waves in high-power 900 MHz industrial applications using an WR975 (R9) rectangular waveguide. The bidirectional detector combines the following components:

• 4-port directional coupler
• Attenuators
• Tunnel diode detectors
• Low noise operational amplifiers

The unit delivers two DC voltages in the range 0 to approximately 9 V. The voltages are functions of the powers associated with waves propagating in opposite directions in the parent waveguide. Standard maximum working powers P_max are 10 kW and 100 kW.

The use of tunnel diodes provides the bidirectional detector with improved temperature stability.