A Wideband Waveguide Launcher in the Interposer for 79 GHz Automotive Radar eWLB Package

This paper proposes a wideband waveguide launcher in the interposer (LiIP) for the embedded wafer-level ball grid array (eWLB) packaging technology at 79 GHz band. The proposed LiIP is made with a High-Density Interconnect (HDI) substrate interposer to support high-count I/Os and routing in the automotive radar module. The designed LiIP exploits a waveguide to Substrate-Integrated-Waveguide (SIW) cavity transition, two central vias, and a quarter wavelength transformer without any extra balun for adapting the differential lines to waveguide transition. Ultimately, a back-to-back version of the proposed structure with $10 \text{mm}\left(2.6 \lambda_{0}\right)$ length has been fabricated and tested for deembedding of the transition loss. The extracted measured transition loss of differential stripline to waveguide was around 2 dB between 72 GHz and 81 GHz.