BD211 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

The detector delivers two well-scaled DC voltages proportional to power of the waves propagating in forward and reverse 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 and fast pulse response.