Millimeter and submillimeter wave instrumentation operating above 100 GHz typically utilizes rectangular waveguide as the primary propagation medium and, consequently, is limited to operation over restricted bands bound by the cut-off frequencies for single- mode propagation. Diplexers provide an option for overcoming the band limitations imposed by conventional waveguide-based instruments. This paper reports, to our knowledge, the first implementation of a prototype “quasi-reflectionless” diplexer based on the reflectionless filter concept developed by Morgan, operating at millimeter-wave frequencies, and utilizing the integration of passive elements onto a silicon-on-insulator platform.
