A Ka-Band Wideband Matched Load Based on Lossy Waveguide Structures

This letter presents the design of a new type of wideband waveguide matched loads. Unlike conventional loads based on absorbing materials, the proposed design relies on conductor loss of the waveguide to achieve the desired absorption level. To increase the waveguide loss and meanwhile maintain a small footprint of the whole device, gap waveguide structures are employed to reduce the group velocity of the wave inside the waveguide. Additionally, the waveguide is formed of walls with low conductivity metal, yielding much higher conductor loss. The waveguide load is designed to have a spiral shape for further reduction on size. The design is demonstrated at Ka-band (26.5-40 GHz) using 3-D printing technology. The measured S-11 of the prototype device is better than -20 dB across the entire Ka-band. This good result validates the proposed concept and reveals that the new lossy wall-based load can be a promising alternative to conventional designs particularly for applications involving high power or demanding superior stability over time.