Abstract: A doppler radar module consisting of transmitting and receiving diodes disposed within adjacent sections of waveguide with the transmitter diode disposed a half wavelength away from a shorting end of the transmitter section of waveguide and a receiver diode disposed a quarter wave from a shorting end of the receiver portion of the waveguide. The receiver section and the transmitter section of the waveguide being separated by a common wall; a coupling aperture disposed in the common wall for coupling a small portion of transmitter energy into the receiver portion of the waveguide and for coupling a maximum of reflected energy into the receiver of waveguide section.