Lin, Yi-TingYi-TingLinKuo, Hung-ChunHung-ChunKuoWu, Po-IPo-IWuJhong, Ming-FongMing-FongJhongWang, Chen-ChaoChen-ChaoWangHung, Chih-PinChih-PinHungWu, Tzong-LinTzong-LinWu2026-03-262026-03-262026-01-2621563950https://www.scopus.com/record/display.uri?eid=2-s2.0-105028785202&origin=resultslisthttps://scholars.lib.ntu.edu.tw/handle/123456789/736818This paper introduces a simple, compact, and low-profile D-band cavity-backed slot antenna-in-package (AiP) designed on a low-cost BT-based organic substrate. A 4 × 8 slot antenna array with a cavity backed is initially analyzed by a substrate integrated waveguide (SIW) feeding structure. In addition to the cavity-backed slot array, the full structure contains a coaxial-like vertical transition and a ground-signal-ground (GSG) probe pad to coaxial transition. The radiation patterns for the antenna fed via the SIW at the core layer and those fed through the low-loss transition from the GSG pad differ by less than 0.1 dBi in realized gain, confirming minimal insertion loss introduced by the transition. The antenna array is verified on a four-layer BT-based organic substrate within a compact footprint, with an electrical size of only 1.48 × 3.18 × 0.18 λ03. The antenna exhibits a peak realized gain of 12.2 dBi and a peak aperture efficiency of 28.1% at 155 GHz. The measured broadside realized gains above 10 dBi maintain across the 152–158 GHz range. The measured farfield results exhibit excellent agreement with the full-wave simulations, validating the accuracy and robustness of the proposed design. These results demonstrate the feasibility of the AiP structure using the low-cost BT-based substrate manufacturing technology as a promising solution for future D-band wireless communication applications.falseAntenna-in-package (AiP)D-bandresonant cavity antennaslot antennasub-THzsubstrate integrated waveguide (SIW)journal article10.1109/tcpmt.2026.36581422-s2.0-105028785202