A Nonreflective Hybrid Stop-Band Filter (Correspondence)

A novel waveguide stop-band filter employing a four terminal hybrid circuit and two lossy cavity resonators has been developed. With this circuit, adjustable frequency sensitive loss can be accomplished with very little reflection similar to directional filter type operation. The circuit utilizes the diplexing characteristics of two adjacent ports of a standard 3-db short slot forward-wave directional coupler. Two identical cavities, each filled with lossy dielectric material, produce the necessary loss. Fig. 1 shows a schematic diagram of the device.