Compact microstrip band-stop filter using IDCLLR

The structure of inter-digital capacitance loaded loop resonator (IDCLLR) is employed for designing microstrip (MS) band-stop filter (BSF), it benefits from its miniaturization and design flexibility due to more structural parameters. Three kinds of IDCLLR-based MS-BSF are presented in this article. Firstly, a 6-stag MS-BSF consisting of a MS-line coupled with uniform pairs of IDCLLRs, and then a 9-stag MS-BSF with nonuniform pairs of IDCLLRs, are designed and tested. Secondly, to replace the IDCLLR by its complementary structure, named as C-IDCLLR with stronger coupling to the MS-line, a 8-stage C-IDCLLR-based MS-BSF with wider stop-band and sharper edge-slope is designed and tested. Finally, the IDCLLR surrounded by meandered MS-line can result in stronger coupling, hence a compact 3-stag IDCLLR-based meandered MS-BSF with good performances is designed and tested.