Linearity Characterization and Optimization of Millimeter-Wave GaN HEMTs
Linearity Characterization and Optimization of Millimeter-Wave GaN HEMTs
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毫米波 GaN HEMT 的线性表征和优化
DOI：
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发表时间：
2011
影响因子：
4.3
通讯作者：
H. A. Hung
中科院分区：
文献类型：
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作者：
J. Qiu;A. Darwish;E. Viveiros;K. Kingkeo;H. A. Hung
本文首次全面研究了GaN/SiC高电子迁移率晶体管（HEMT）在毫米波（mmW）下的线性特性。使用AM-AM，AM-PM，双音和16正交幅度调制（16 QAM）调制波形测量在31.5 GHz的三个来源的类似大小的设备进行比较。此外，误差矢量幅度（EVM）和频谱再生[相邻信道功率比（ACPR）]的数据也提出。使用与mmW（50 GHz）负载牵引系统集成的独特数字波形系统，在不同的操作级别（A、AB和B）下测量HEMT的结果。在所有器件中，观察到“平衡AB”（b-AB）类器件偏置条件，其中线性度和效率同时优化。定义并计算了每个类别的基于单音功率测量的线性品质因数FOMlinearity。FOM线性度与双音和数字调制驱动条件下HEMT的线性度性能密切相关。与A类相比，在固定输出功率下，b-AB类的互调失真改善了5-10 dB，漏极效率提高了1.2倍至1.9倍。该表征方法和推导的FOM线性度将有利于单片微波集成电路（MMIC）设计人员优化GaN HEMT的操作。结果还表明，GaN HEMT可以提供适用于卫星通信等应用的线性特性，同时保持高效率和功率密度。
This paper presents the first comprehensive study of the linearity characteristics of GaN/SiC high-electron mobility transistors (HEMTs) at millimeter-wave (mmW). Similar size devices from three sources are compared using AM-AM, AM-PM, two-tone, and 16-quadrature-amplitude modulation (16QAM) modulated waveforms measurements at 31.5 GHz. Additionally, error vector magnitude (EVM) and spectrum regrowth [adjacent channel power ratio (ACPR)] data are also presented. The results were measured, using a unique digital waveform system integrated with a mmW (50-GHz) load-pull system, for HEMTs at different classes of operation: A, AB, and B. In all devices, it is observed that a “balanced AB” (b-AB) class of device bias condition where linearity and efficiency are simultaneously optimized. A linearity figure of merit FOMlinearity, based on single-tone power measurements, is defined and calculated for each class. The FOMlinearity closely correlates with linearity performance of the HEMT under two-tone and digitally modulated drive conditions. Compared with class A, at a fixed output power, a b-AB class showed a 5-10-dB improvement in intermodulation distortions, combined with 1.2 × to 1.9 × enhancement in drain efficiency. The characterization methodology and derived FOMlinearity should benefit monolithic microwave integrated circuit (MMIC) designers to optimize the operation of GaN HEMTs. The results also indicate that GaN HEMTs can provide linearity characteristics suitable for applications such as satellite communications, while maintaining high efficiency and power density.