Implementation of Reduced-Size Dual-Mode Ring Filters in LTCC and MMIC Processes at Millimeter Wave Frequencies

Millimeter-wave applications of the reduced-size dual-mode ring filters are investigated in this paper using low-temperature co-fired ceramics (LTCC) and MMIC processes. The LTCC version of the reduced-size ring filters is designed at 28 GHz, and the monolithic version is fabricated on 4-mil GaAs substrate. Insertion losses of under 3 dB are achieved. Coupling due to extensive size reductions and process variations have various effects of the filter performance, and are observed in the experiments. These results demonstrate the performance of reduced-size ring filters in millimeter-wave applications, and also suggest the possibility of system-on-package (SOP) and system-on-chip (SOC) of this miniature filter structure