A compact 20/30 GHz diplexer based on substrate integrated waveguide (SIW) cavities and grounded coplanar waveguide (GCPW) feed lines is proposed. It features additional in-phase reactive power splitting in both passbands by exploiting symmetries. The component is realized in a vertically cascaded configuration using multilayer printed circuit board (PCB) technology, achieving a footprint of only 6×8 mm2. The compactness of the diplexer enables utilization in highly integrated applications such as shared aperture transmit/receive (Tx/Rx) phased arrays.
