Abstract: A hollow cylinder that has a permittivity greater than the permittivity of air is coaxially disposed within a waveguide with the proximal end of the cylinder coplanar with one end of the waveguide. The cylinder has a metal clad surface wherein a plurality of tapered slots that are narrowest at the proximal end of the cylinder and widest at the distal end thereof. The slots are coupled to respective amplification devices, thereby causing the waveguide to be terminated in an impedance substantially equal to impedances of the devices connected in series. Microwave power is transmitted through the waveguide via propagation of a wave in the TE.sub.01 mode. When the wave propagates to the cylinder, the power is transmitted to the devices via the electric fields within the slots at the proximal end of the cylinder. The wave propagates from the cylinder in response to the power being provided by the devices.