Low Loss Air-Filled Transmission Lines in LTCC Technology

The design of air-filled transmission lines in Low Temperature Co-Fired Ceramic (LTCC) technology is introduced. Striplines surrounded by air cavities inside two different multilayered LTCC substrates are described and their attenuation coefficients are calculated based on 3D field electromagnetic simulations. Transitions from these buried striplines to upper layers, for interconnection purpose, are also characterized. Compared to conventional dielectric-filled architectures, the proposed air-filled guiding structures, including transitions to upper layers, demonstrate significant gains on the attenuation coefficients from 1 GHz to 15 GHz. Simulation results show that their total attenuations are lower than 0.13 dB with better than 15 dB as return loss.