A substrate-integrated-waveguide dual-band bandpass filter based on signal-interference principles

Contrary to conventional RF filtering devices that are based on electromagnetically-coupled resonators, signal-interference microwave filters exploit constructive and destructive interactions of signals that propagate along different electrical paths of the filter volume. To date, most of signal-interference filters have been implemented in planar technologies. However, their operational principles are general and can hence be extrapolated to non transverse-electromagnetic-mode (TEM)/quasi-TEM technologies - either mixed or separate ones -. This paper reports on the design and manufacturing of a C-band signal-interference dual-band bandpass filter based on a half-mode substrate-integrated-waveguide (HMSIW) directional coupler. The obtained experimental results are in close agreement both with the theory and the simulations, which reveals that signal-interference filters can be extended to nonplanar technologies. Their potential for multi-stage higherorder filter realizations is also demonstrated.