Small-Reflected Substrate Integrated Waveguide Termination With Multi-Step Shape And Absorbing Material

A planar wideband substrate integrated waveguide (SIW) termination with multi-step shape and absorbing material is reported. Early reported absorbing material based SIW terminations exhibit fractional bandwidth (FBW) less than 45%. To broaden bandwidth, the multi-section stepped-impedance transformation is introduced into the design of SIW termination based on the theory of small reflection. The multi-step shape such as trident is used to mold the absorbing material, so that the impedance matching between the substrate and absorbing material can be improved and achieve a wider bandwidth. Measurement of the fabricated prototype exhibits a FBW over 70% with return loss better than 17dB, as well as system integration capability and low structure complexity.