LTCC FOLD-BACK BANDPASS FILTER DESIGNED WITH CAPACITIVELY LOADED STUBS

This study presents a design of a compact stub-type bandpass fllter with capacitively loaded stubs and a fold-back structure. This paper employed the fabrication process of low- temperature co-flred ceramic (LTCC) for fllter realization of a multi- layer structure. The proposed fllter structure required adding end capacitors to stubs to extend their electrical length, while achieving a length reduction of 30%. This study provided design curves to determine the dimensions of the end capacitor for reaching maximum electrical length extension. In addition, a fold-back conflguration was applied to halve the fllter size. An experimental fllter operating at 5.8GHz was fabricated and measured to validate the design concept, achieving a highly compact size of 14:3 £ 8:2 £ 0:76mm 3 .