Jang Sheng-Lyang, Huang Ching-Yen, Yang Tzu Chin, Lu Chien-Tang
Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 106335, Taiwan.
Micromachines (Basel). 2025 Jul 28;16(8):869. doi: 10.3390/mi16080869.
With their superior switching speed, GaN high-electron-mobility transistors (HEMTs) enable high power density, reduce energy losses, and increase power efficiency in a wide range of applications, such as power electronics, due to their high breakdown voltage. GaN-HEMT devices are subject to long-term reliability due to the self-heating effect and lattice mismatch between the SiC substrate and the GaN. Depletion-mode GaN HEMTs are utilized for radio frequency applications, and this work investigates three wide-bandgap (WBG) GaN HEMT fixed-frequency oscillators with output buffers. The first GaN-on-SiC HEMT oscillator consists of an HEMT amplifier with an feedback network. With the supply voltage of 0.8 V, the single-ended GaN oscillator can generate a signal at 8.85 GHz, and it also supplies output power of 2.4 dBm with a buffer supply of 3.0 V. At 1 MHz frequency offset from the carrier, the phase noise is -124.8 dBc/Hz, and the figure of merit (FOM) of the oscillator is -199.8 dBc/Hz. After the previous study, the hot-carrier stressed RF performance of the GaN oscillator is studied, and the oscillator was subject to a drain supply of 8 V for a stressing step time equal to 30 min and measured at the supply voltage of 0.8 V after the step operation for performance benchmark. Stress study indicates the power oscillator with buffer is a good structure for a reliable structure by operating the oscillator core at low supply and the buffer at high supply. The second balanced oscillator can generate a differential signal. The feedback filter consists of a left-handed transmission-line network by cascading three unit cells. At a 1 MHz frequency offset from the carrier of 3.818 GHz, the phase noise is -131.73 dBc/Hz, and the FOM of the 2nd oscillator is -188.4 dBc/Hz. High supply voltage operation shows phase noise degradation. The third GaN cross-coupled VCO uses 8-shaped inductors. The VCO uses a pair of drain inductors to improve the -factor of the tank, and it uses 8-shaped inductors for magnetic coupling noise suppression. At the VCO-core supply of 1.3 V and high buffer supply, the FOM at 6.397 GHz is -190.09 dBc/Hz. This work enhances the design techniques for reliable GaN HEMT oscillators and knowledge to design high-performance circuits.
由于具有高击穿电压，氮化镓高电子迁移率晶体管（HEMT）凭借其卓越的开关速度，在诸如电力电子等广泛应用中实现了高功率密度、降低了能量损耗并提高了功率效率。由于自热效应以及碳化硅衬底与氮化镓之间的晶格失配，氮化镓-HEMT器件面临长期可靠性问题。耗尽型氮化镓HEMT用于射频应用，本工作研究了三种带输出缓冲器的宽带隙（WBG）氮化镓HEMT固定频率振荡器。第一个碳化硅基氮化镓HEMT振荡器由一个带有反馈网络的HEMT放大器组成。在0.8V的电源电压下，单端氮化镓振荡器能够在8.85GHz产生信号，并且在3.0V的缓冲器电源下还能提供2.4dBm的输出功率。在偏离载波1MHz频率偏移处，相位噪声为-124.8dBc/Hz，该振荡器的品质因数（FOM）为-199.8dBc/Hz。在先前的研究之后，对氮化镓振荡器的热载流子应力射频性能进行了研究，该振荡器在8V的漏极电源下施加30分钟的应力步长时间，并在步长操作后于0.8V的电源电压下进行性能基准测量。应力研究表明，带有缓冲器的功率振荡器是一种可靠的结构，通过在低电源下操作振荡器核心并在高电源下操作缓冲器来实现。第二个平衡振荡器能够产生差分信号。反馈滤波器由级联三个单元的左手传输线网络组成。在偏离3.818GHz载波1MHz频率偏移处，相位噪声为-131.73dBc/Hz，第二个振荡器的FOM为-188.4dBc/Hz。高电源电压操作会导致相位噪声恶化。第三个氮化镓交叉耦合压控振荡器使用8字形电感。该压控振荡器使用一对漏极电感来提高储能电路的品质因数，并使用8字形电感来抑制磁耦合噪声。在1.3V的压控振荡器核心电源和高缓冲器电源下，6.397GHz处的FOM为-190.09dBc/Hz。这项工作增强了可靠氮化镓HEMT振荡器的设计技术以及设计高性能电路的知识。
