TY - GEN A1 - Krishnaji Rao, Megha A1 - Wentzel, Andreas A1 - Hoffmann, Thomas A1 - Schellhase, Lars A1 - A. Chevtchenko, Serguei A1 - Yazdani, Hossein A1 - Rudolph, Matthias T1 - Digital GaN-based transceiver architectures for sustainable 5G networks T2 - International journal of microwave and wireless technologies N2 - This paper presents two distinct configurations of a GaN-based digital transceiver (TRx) to evaluate their performance and integration efficiency. The first configuration, features a novel low-noise amplifier with integrated switching capability (LNAiS) and a digital class-E power amplifier (PA) on a single compact chip. The LNAiS eliminates the need for an external antenna switch, reducing module complexity and chip size while maintaining high performance. It achieves a gain of 12.7 dB and a noise figure of 3 dB at 4.7 GHz in Rx mode and provides over 20 dB isolation in Tx mode across 4.7–7.4 GHz. The digital PA demonstrates flexibility and efficiency, achieving 46% and 23% efficiencies for 20 MHz LTE and OFDM signals, respectively, and 22% for a 240 MHz OFDM signal with 10 dB PAPR. The second configuration integrates the same concept of digital PA with a standard LNA and an SPDT switch (LNAsS), achieving a gain of 24.8 dB and a noise figure of 2.65 dB at 4.2 GHz. This work highlights the trade-offs between these two architectures and demonstrates that the LNAiS-based approach drives the development of greener, more flexible, compact,lower-complexity, and cost-effective transceivers for 5G networks. KW - GaN KW - HEMT KW - MMIC KW - Transceiver KW - FEM KW - LNA KW - PA KW - spdt switch KW - Digital KW - PWM KW - Class-E KW - 5G Y1 - 2025 U6 - https://doi.org/10.1017/S1759078725102262 SN - 1759-0787 SP - 1 EP - 9 PB - Cambridge University Press (CUP) CY - Cambridge ER - TY - GEN A1 - Beleniotis, Petros A1 - Zervos, Christos A1 - Krause, Sascha A1 - Yazdani, Hossein A1 - Rudolph, Matthias T1 - Traps in GaN HEMTs : from characterization to model development and device optimization T2 - 2025 IEEE BiCMOS and Compound Semiconductor Integrated Circuits and Technology Symposium (BCICTS) N2 - This paper reviews a comprehensive strategy designed to address the impact of traps across the entire field of GaN HEMT operation. It begins with the characterization of trap levels and the measurement of trap time constants. The study then progresses to TCAD simulations to examine the location of the observed trap levels and their effect on device performance. Finally, it introduces the development of a compact trap model grounded in Shockley-Read-Hall statistics. The proposed model is capable of accurately predicting trapping effects across all combinations of voltage, temperature, and time. The paper concludes by highlighting the synergy TCAD-compact-model, underscoring its utility in device optimization schemes. KW - GaN KW - Traps KW - Microwave KW - TCAD KW - ASM-HEMT Y1 - 2025 SN - 979-8-3315-9172-4 U6 - https://doi.org/10.1109/BCICTS63111.2025.11211504 SP - 1 EP - 8 PB - IEEE CY - Piscataway, NJ ER - TY - GEN A1 - Rao, Megha Krishnaji A1 - Beleniotis, Petros A1 - Hoffmann, Thomas A1 - Yazdani, Hossein A1 - Wentzel, Andreas A1 - Rudolph, Matthias T1 - Switch-integrated GaN LNAs : a technology-focused analysis T2 - 2025 20th European Microwave Integrated Circuits Conference (EuMIC) N2 - This paper presents the first circuit-level analysis of a two-stage GaN-HEMT LNA with an integrated switch, comparing two distinct technologies: one with a standard passivation layer (Type A) and another featuring an advanced passivation layer (Type B). Through a detailed evaluation of their performance in both amplification and isolation modes, the study highlights Type B as a significant advancement over Type A. Leveraging technological enhancements, including an improved passivation layer and slightly optimized component matching, Type B demonstrates superior performance. The results are compelling, with Type B achieving a gain of 19 dB, a low noise figure of 1.17dB, and small-signal isolation exceeding 30 dBm at 5.2 GHz. These achievements establish Type B as a formidable option for future 5G telecommunication systems, offering a performance that challenges traditional designs that use separate switches. Y1 - 2025 SN - 978-2-87487-082-8 U6 - https://doi.org/10.23919/EuMIC65284.2025.11234676 SP - 29 EP - 32 PB - IEEE CY - Piscataway, NJ ER - TY - GEN A1 - Okocha, Jonathan A1 - Andrei, Cristina A1 - Rudolph, Matthias T1 - On the repeatability of low cost varactor—based RF impedance tuners T2 - 2025 55th European Microwave Conference (EuMC) N2 - This paper introduces a concise methodology for assessing the repeatability of low-cost, varactor-based RF impedance tuners by employing a dB-based metric that quantifies how accurately each tuner reproduces a target impedance over repeated cycles. Both blocked and cyclical measurement strategies are used to highlight large impedance transitions near high-reflection states that exacerbate non-idealities. In addition, the method rigorously characterizes issues such as systematic offsets, drift, and hysteresis, common challenges that can impair tuner performance, allowing targeted improvements. Demonstrations with a BST varactor prototype underscore the importance of identifying and quantifying these effects to ensure consistent tuner performance in real-world RF testing environments. KW - RF impedance tuning KW - Tuner repeatability KW - Mechanical tuner KW - Electronic tuners KW - Load-pull KW - Measurement methodology KW - Smith chart tuners KW - dB-based metric KW - Tuner accuracy Y1 - 2025 SN - 978-2-87487-081-1 U6 - https://doi.org/10.23919/EuMC65286.2025.11234977 SP - 683 EP - 686 PB - IEEE CY - Piscataway, NJ ER - TY - CHAP A1 - Gailing, Ludger A1 - Naumann, Matthias A1 - Rudolph, David T1 - Local and regional conflicts in the energy transition T2 - Reference module in materials science and materials engineering N2 - Energy transitions are accompanied by a range of conflicts, which mostly occur at local and regional scales. To help understand these, this chapter provides a typology of energy conflicts, of which the most common are distribution and procedural conflicts. Energy conflicts entail material, spatial, temporal and actor dimensions. For both major types of energy conflict and their different dimensions, the chapter provides empirical examples from Denmark and the United Kingdom. Energy conflicts are a challenge for energy transitions, but they are also drivers of social change, which are inherent in the pluralistic structure of modern societies. KW - Energy geography KW - Infrastructure planning KW - Landscape KW - Localism KW - Regional development KW - Renewable energies KW - Wind energy Y1 - 2025 SN - 978-0-12-803581-8 U6 - https://doi.org/10.1016/B978-0-443-29210-1.00073-X SP - 1 EP - 9 PB - Elsevier BV CY - Amsterdam ER -