3D transition between thin and thick waveguides to interconnect chip and antenna-in-package

It is very challenging to efficiently radiate millimeter-wave signals from silicon chips, especially from standard CMOS chips which use low-resistivity lossy silicon substrates. To address this issue, this paper describes a novel 3D transition which efficiently couples an on-chip signal and then directly feeds an in-package antenna. To verify this idea with low cost, a transition between thin and thick waveguides is studied using printed circuit boards. This transition features an insertion loss of 1.4 dB at 77 GHz and a 15-dB return-loss bandwidth of 6 GHz. Furthermore, this transition is inherently integrated to feed a hollow horn, and the whole antenna achieves more than 10 dBi gain from 74.9 to 79.3 GHz.