Enhanced Performance of Multilayer Bandpass Filter Using Slow-Wave Empty Substrate- Integrated Waveguide (SW-ESIW)

In this letter, two compact and high-performance filters based on multilayer slow-wave empty substrate-integrated waveguide (SW-ESIW) are presented. SW-ESIW, which contains the air cavity and a bottom layer including several rows of internal metallized via holes, provides a compromise between insertion loss and footprint. It is the first time that SW-ESIW is used to implement compact filters with multilayer air cavity. The proposed filters are simulated, fabricated, and measured. The measurements are consistent with simulations, indicating that the proposed filters can be reduced more than 35% in dimension compared to the same filters in ESIW. Based on the SW-ESIW technology, the proposed multilayer filters realize the advantages of low insertion loss and miniaturization, and express the tremendous potential on applications to complex and high-performance microwave circuits and systems.