A matched load for post-wall waveguide (SIW; Substrate Integrated Waveguide) is presented. It consists of an electrically-shorted post-wall waveguide and a rectangular thin-film resistor sheet on the surface of the waveguide, resulting in a quite compact structure without three-dimensional bulky absorber as in conventional waveguide matched loads. A fabricated X-band matched load has achieved less than -20dB reflection in more than 20% relative bandwidth.
