LTCC bandpass filter using 3D coupled helical inductors

A new low-temperature co-fired ceramic (LTCC) bandpass filter using three-dimensionally coupled helical inductors is presented. The resonator is a via-connected multilayer helical inductor and the filter uses mixed coupling between face-to-face inductors. The fabricated filter exhibits the center frequency of 5.8 GHz, 3-dB bandwidth of 800 MHz, and the insertion loss of 1.9 dB. The size of the active region is 1.7 × 2.3 × 0.8 mm³. The measured results are consistent with the three-dimensional electromagnetic simulation and the equivalent circuit modeling.