Compact dual-passband LTCC filter exploiting eighth-mode SIW and SIW hybrid with coplanar waveguide

A compact dual-passband low-temperature ceramic con-fired (LTCC) filter is proposed. Its electrical size is reduced by exploiting an eighth-mode substrate integrated waveguide (SIW) and a conventional SIW hybrid with a coplanar waveguide (CPW). The filter is fabricated on multilayer ceramic, which makes the filter even more compact. The filter was fabricated and measured. The measured results show that the filter has dual-passband, the first passband is centred at 8.0 GHz with 0.95 GHz 3 dB bandwidth, and the second passband is centred at 11.1 GHz with 0.41 GHz 3 dB bandwidth. The filter has low passband insertion and sharp roll-off characteristics at the transition band. The volume of the filter is only 9.6 × 9.6 × 1.4 mm³.