https://scholarworks.unist.ac.kr/handle/201301/38 2026-03-31T05:07:10Z https://scholarworks.unist.ac.kr/handle/201301/90795 Title: Advances and Future Challenges in Monolithic 3D Integrated Logic, Power, and Optoelectronics Technologies for Tightly Interconnected Intelligent Systems Author(s): Jung, Haksoon; Choi, Joonghoon; Baek, Seunghun; Shin, Bong Gyu; Song, Young Jae; Jung, Hanggyo; Kim, JoHyeon; Jeon, Jongwook; Kim, Gyumin; Park, Heechun; Lee, Yeonjoo; Yoo, Jinkyoung; Lee, Jae-Hyun; Kim, Hyungwoo; Kang, Kibum; Jeong, Jaeyong; Kim, Sang Hyeon; Bae, Joohan; Kim, Chang Soo; Yang, Won Kwang; Lee, Sungjoo; Kwon, Jiwook; Kim, Byung-Sung; Han, Jae-Hoon; Kim, Hyung-Jun; Yoon, Hoon Hahn; Kwon, Jimin; Hong, Young Joon Abstract: The emergence of ultralarge-scale hardware systems for artificial intelligence is driving demand for high-performance heterogeneous integration. At the heart of these systems lies the maximization of computational capability through high data bandwidth, necessitating interconnects that either increase the number of links between tiers and chips or enhance the data transfer rate of each link. Monolithic three-dimensional (M3D) integration, particularly with two-dimensional (2D) materials, offers ultradense intertier vias and multifunctional devices within back-end-of-line-compatible processes, enabling compact vertical stacking of logic and memory. A critical challenge in this architecture is thermal management, requiring cross-layer electro-thermal analysis and codesign with integrated power regulation. In parallel, photonic integrated circuits provide low-latency, energy-efficient interchip communication by overcoming the traditional bandwidth limitation imposed by electrical signal loss, and their advantages become increasingly significant as the communication distance increases. Emerging concepts, including spectrally tunable 2D photodetectors and vertically stacked microlight-emitting-diode-photodiode transceivers, further enhance scalability by eliminating reliance on external lasers. This Review article highlights the convergence of M3D integration, 2D materials, and photonic interconnects, while outlining challenges of material compatibility, process scalability, and system-level codesign that must be addressed to realize a unified framework for next-generation computing and communication systems beyond conventional Si scaling. 2026-02-28T15:00:00Z https://scholarworks.unist.ac.kr/handle/201301/90791 Title: Detection of apnea and hypopnea events using a wireless Abdomen-Worn sensor with SpO2 integration Author(s): Dang, Thi Hang; Min, Hyung-ki; Sung, Nam-hwan; Kim, Seong-mun; Yoon, Heein; Bien, Franklin Abstract: Purpose Polysomnography is the gold standard for diagnosing sleep apnea (SA), but it is costly and not widely available. Home sleep apnea testing (HSAT) offers a more accessible, lower-cost alternative. Type III HSAT typically uses nasal pressure sensors, respiratory inductance plethysmography (RIP) belts, and pulse oximetry; however, nasal sensors and RIP belts may be uncomfortable or unsuitable for some patients. This study assessed whether apnea and hypopnea events can be detected using a wireless abdomen-worn sensor (Soomirang) combined with SpO(2) monitoring, eliminating the need for nasal pressure sensors or RIP belts. Methods Data from 37 participants were collected using the Soomirang device and a typical type III HSAT (AL). Two models were developed for apnea and hypopnea event detection: SoomOxy, combining abdominal and body movement data with SpO(2), and Soom, using abdominal and body movement data alone. Their performance was evaluated against AL. Results SoomOxy demonstrated strong agreement with AL, achieving an area under the curve of 0.9447 for apnea and 0.8702 for hypopnea detection, a predicted apnea hypopnea index correlation of 0.96, and an average accuracy of 0.8286 across all severity categories. The SoomOxy outperformed Soom model in detecting hypopnea events. Conclusion A wireless abdomen-worn sensor combined with SpO(2) monitoring can accurately detect and classify apnea and hypopnea events without nasal pressure and RIP belts, offering a practical and more comfortable alternative to conventional HSAT setups. 2026-02-28T15:00:00Z https://scholarworks.unist.ac.kr/handle/201301/90624 Title: Sequentially Fed Rhombus Patch Subarray for Wide-Angle Circularly Polarized Antenna-in-Package Author(s): Lee, Changhee; Kang, Wootaek; Heo, Jin Myeong; Byun, Gangil Abstract: This paper presents a sequentially fed rhombus patch subarray for a wide-angle circularly polarized (CP) antenna-in-package in Ka-band low-Earth-orbit satellite communications. The proposed design approach is based on integrating a sequentially fed patch array, showing broadband and wide-angle CP performance, into a hexagonal lattice. Three rhombus patches are arranged with 120 degrees rotational symmetry, each aperture-coupled by a feeding network consisting of a three-way power divider and 120 degrees phase delay lines. This enables maximum radiation and CP property in the given hexagonal lattice. Moreover, due to the proximity effect between the tightly coupled patches, the antenna size can be reduced to 0.58 lambda(0) diameter (lambda(0) is a free-space wavelength at 28 GHz), while mitigating the mutual coupling effect on CP radiation by exciting a pair of patches simultaneously. The honeycomb-shaped array configuration enables symmetric beam scanning and maintains CP properties for wide-angle beamforming while preventing grating lobes. The proposed antenna is fabricated as a 4 x 4 array with dimensions of 2.2 lambda(0)x 2.7 lambda(0) and validated through measurement. The measured averaged matching bandwidth is 2.6 GHz (27.1-29.7 GHz), and port isolation is higher than 30 dB. The measured 3-dB axial ratio bandwidth is 1.2 GHz, with stable beamforming gains of 11.93 dBic, 12.27 dBic, and 8.72 dBic at theta(0) = 0 degrees , 15 degrees , and 30 degrees . 2025-12-31T15:00:00Z https://scholarworks.unist.ac.kr/handle/201301/90623 Title: Sequentially Fed Rhombus Patch Subarray for Wide-Angle Circularly Polarized Antenna-in-Package Author(s): Lee, Changhee; Kang, Wootaek; Heo, Jin Myeong; Byun, Gangil Abstract: This paper presents a sequentially fed rhombus patch subarray for a wide-angle circularly polarized (CP) antenna-in-package in Ka-band low-Earth-orbit satellite communications. The proposed design approach is based on integrating a sequentially fed patch array, showing broadband and wide-angle CP performance, into a hexagonal lattice. Three rhombus patches are arranged with 120 degrees rotational symmetry, each aperture-coupled by a feeding network consisting of a three-way power divider and 120 degrees phase delay lines. This enables maximum radiation and CP property in the given hexagonal lattice. Moreover, due to the proximity effect between the tightly coupled patches, the antenna size can be reduced to 0.58 lambda(0) diameter (lambda(0) is a free-space wavelength at 28 GHz), while mitigating the mutual coupling effect on CP radiation by exciting a pair of patches simultaneously. The honeycomb-shaped array configuration enables symmetric beam scanning and maintains CP properties for wide-angle beamforming while preventing grating lobes. The proposed antenna is fabricated as a 4 x 4 array with dimensions of 2.2 lambda(0)x 2.7 lambda(0) and validated through measurement. The measured averaged matching bandwidth is 2.6 GHz (27.1-29.7 GHz), and port isolation is higher than 30 dB. The measured 3-dB axial ratio bandwidth is 1.2 GHz, with stable beamforming gains of 11.93 dBic, 12.27 dBic, and 8.72 dBic at theta(0) = 0 degrees , 15 degrees , and 30 degrees . 2025-12-31T15:00:00Z