Prof. Jimenez of CEA-Leti

Energy-Efficient Transceivers Presentation Preparation
The meeting focused on preparing for a presentation by Professor Jose Luis Gonzalez Jimenez on energy-efficient transceivers for D-band and sub-terahertz communication. Malvin and Jose resolved technical issues with audio and screen sharing, and Yusnita introduced Professor Gonzalez as the moderator for the session. The presentation was confirmed to be delivered remotely via Zoom, with an expected attendance of 20-30 participants, and Professor Gonzalez began sharing his slides to start the presentation.

High-Capacity Wireless Radio Links
Prof. Jose presented on implementing high-capacity wireless radio links exceeding 100 gigabits per second, focusing on two main use cases: telecommunication infrastructure and smart factories. He explained that while higher frequencies provide the necessary bandwidth for such high data rates, they come with increased propagation loss, requiring careful consideration of transmit power, antenna gain, and distance. The presentation included an illustrative calculation showing how a link at 2.4 GHz could reach 4 kilometers, but would be limited to just 65 meters at 140 GHz under similar conditions. Jose noted that he would cover solutions for extending range and implementing non-line-of-sight communication in the latter part of the lecture.

Wireless Communication System Design Analysis
Prof. Jose presented a detailed analysis of wireless communication system design, focusing on bandwidth optimization and power consumption considerations. He explained the theoretical limits of data rates using Shannon capacity equations and demonstrated that for a 100 Gbps target at 200 meters, optimal performance requires operating at 140 GHz with 25 GHz bandwidth using 16QAM modulation. The discussion then shifted to power efficiency in data converters, where Jose showed that using multiple lower-speed converters is more energy efficient than a single high-speed converter. Finally, he outlined a multi-channel aggregation architecture that uses a double-step conversion approach with 8 local oscillator frequencies to efficiently handle 16 baseband channels, presenting both circuit designs and measurement results for the implemented transmitter and receiver modules.

Multi-Channel Wireless Communication System
Prof. Jose presented a comprehensive overview of a multi-channel wireless communication system operating from baseband to D-band frequencies, demonstrating 112 Gbps data transmission with 16-QAM modulation over 2.5 meters. The system uses channel aggregation architecture with custom multi-channel downconverters, integral frequency multiplication for local oscillator generation, and electromagnetic lens antennas to achieve high antenna gain. The presentation covered technical details including phase noise characteristics, EVM measurements, and energy efficiency of 33 picojoules per bit, along with discussion of scaling challenges for higher frequencies and future research directions including the use of external power amplifiers and active reflection surfaces for smart factory applications.

D-Band Oscillator Distribution Challenges
Prof. Jose discussed the challenges of distributing local oscillators at high frequencies, explaining that long distribution paths require buffers which contribute to phase noise. He detailed the power limitations of CMOS technology at D-band, noting that saturated output power is around 11 dBm with useful power about 10 dB lower, close to technology limits. Jose recommended using CMOS for complex architectures and combining it with external power amplifiers rather than trying to achieve high output power directly in CMOS. When asked about D-band implementation for cellular backhaul, Jose confirmed it will be necessary for operators needing to increase capacity by a factor of 10 beyond current E-band links. He also explained the differences between digital beamforming, analog beamforming, and hybrid beamforming approaches, noting that full digital beamforming provides the most flexibility for massive MIMO systems.

Biography:

José Luis González-Jiménez is a Fellow and Research Director at CEA-Leti. He received the Diploma degree in telecommunication engineering from Ramon Llull University, Barcelona, Spain, in 1992, the M.Sc. degree in Telecommunications Engineering and the Ph.D. degree (Hons.) in electronic engineering from the Universitat Politecnica de Catalunya (UPC), Barcelona, in 1994 and 1998, respectively. He attained the “Habilitation à Diriger des Recherches – HDR” degree from Grenoble University, Grenoble, France, in 2013. From January to July 1999, he worked as a Guest Researcher with the University of Arizona, Tucson, AZ, USA, where he collaborated with Motorola on the design of high-speed digital-to- analog converters. From September 2007 to August 2008, he was a Visiting Researcher with the STMicroelectronics/CEA-Leti joint Advanced Research Laboratory, Minatec, Grenoble, where he was engaged in research on the design of millimeter-wave oscillators and substrate noise coupling in millimeter-wave CMOS integrated circuits (ICs). Until 2011, he was a full-time Associate Professor with the Department of Electronic Engineering, Universitat Politecnica de Catalunya, Barcelona. From 2015 to 2019, he was the Deputy Head of the RFIC Design Laboratory, CEA-Leti, Grenoble. He is also an Invited Lecturer at the Phelma Engineering School, Grenoble-Alpes University. He has been leading and participating in several international research projects and contracts with companies. He is the author of two books, three book chapters, more than 40 international journal articles, and more than 120 conference papers. He holds 23 patents. His research interests include very large-scale integration circuits and systems, mixed-signal/RF,  millimeter-wave and sub-THz ICs, silicon photonics, and signal and power integrity in SoC and RFICs. Dr. González-Jiménez was awarded a Fulbright Fellowship and regularly collaborates as a reviewer in journals, including IEEE Journal of Solid-State Circuits, IEEE Transactions of Circuits and Systems (I and II), IEEE Microwave and Wireless Components Letters, Electronics Letters, and IEEE Transactions on Microwave Theory and Techniques, and serves regularly for the technical program committee of several international conferences, including ISSCC, ESSERC, EuMW and IMS. From 2023 to 2025 he was the IEEE CAS society representative at the Steering Committee of the IEEE Future Networks Technical Community. He is a IEEE Senior Member and a EUMA Member.

Address:CEA-Leti, RFIC Design Laboratory, 17 Rue des Martyrs, , Grenoble, France, 38054