Research on Ka-band Enhanced Load Modulation Ultra-wideband High-efficiency Doherty Power Amplifier
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摘要: Ka波段是未来新一代高通量卫星的核心频段,卫星通信发射系统对功率放大器提出了高回退效率的严苛要求。Doherty功率放大器(DPA)通过有源负载调制显著提高了功率回退状态下的工作效率,但Doherty架构的固有阻抗变换网络严重限制了其工作带宽,同时,其在毫米波段的饱和与回退效率均大幅下降,这成为制约其在毫米波高通量卫星通信系统中应用的关键瓶颈。针对上述问题,本文提出了一种超宽带增强型有源负载调制技术,有效突破Doherty功率放大器带宽和回退效率相互制约的瓶颈,实现毫米波Doherty架构的效率增强和带宽扩展。同时,创新的提出了一种超宽带相位补偿非等分功率分配网络,扩展了高效率带宽,同时缩小了芯片面积。为验证所提理论,基于0.15 μm GaN工艺,设计了一款毫米波超宽带高效率Doherty功率放大器芯片,最终在24-33 GHz(相对带宽达到31.6%)的超宽频带内,实现了21.8-23.8 dB的小信号增益,28.9-31.0 dBm的饱和输出功率,饱和功率附加效率(PAE)为25.2%-33.5%,6dB回退PAE为15.5%-19.8%。在目前所报道的相近频带的毫米波GaN Doherty功放中,具有最高的小信号增益及饱和PAE,高的饱和输出功率和6 dB回退PAE等一系列优异性能,同时在目前所报道的2-3级DPA芯片中具有最小的芯片面积。
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关键词:
- 卫星通信 /
- 毫米波 /
- Doherty功率放大器 /
- 超宽带 /
- 高效率
Abstract:Objective The Ka band has become the main direction of satellite communication, which requires the core component of its transmission system, the millimeter-wave power amplifier, to be more compact in size. Meanwhile, to maximize spectral efficiency, millimeter-wave satellite communication signals will have a high peak-to-average power ratio (PAPR). Therefore, it is crucial to design a millimeter-wave power amplifier with high saturation efficiency, high back-off efficiency, and compact size. Doherty power amplifiers (DPAs) are renowned for their high efficiency and excellent linearity in power back-off states and have become a key solution to these problems. However, Doherty power amplifiers face the issue of a relatively narrow operating frequency band. Moreover, when the operating frequency extends to the millimeter-wave band, their efficiency also drops significantly. Thus, overcoming the narrowband and low efficiency problems of millimeter-wave Doherty power amplifiers is a critical challenge that needs to be addressed urgently in the satellite communication transmission chain. Methods This paper presents an ultra-wideband enhanced active load modulation technique that effectively addresses the fundamental trade-off between bandwidth and back-off efficiency in Doherty power amplifiers. The proposed technique enables optimal impedance transformation for both carrier and peak amplifiers across an ultra-wide frequency band, while introducing an adjustable fundamental impedance bias matching network (ITBN) and a dual-drive impedance regulation mechanism. This improvement enhances load modulation performance while extending the bandwidth of load modulation behavior, achieving simultaneous efficiency enhancement and bandwidth expansion in the millimeter-wave Doherty architecture. Furthermore, a broadband phase compensation technique is integrated with an unequal power division network. This integration facilitates sufficient load modulation over ultra-wide bandwidth while maintaining precise phase difference compensation between carrier and peak paths. The proposed ultra-wideband phase-compensated power division network extends the high-efficiency bandwidth while reducing the overall chip area. Results and Discussions A millimeter-wave ultra-wideband high-efficiency Doherty power amplifier chip was designed and fabricated based on a 0.15-μm GaN process to validate the proposed technology. Within the ultra-wide frequency band of 24–33 GHz, the fabricated chip achieves a small-signal gain of 21.8-23.8 dB with excellent gain flatness (±1 dB). It delivers a saturated output power of 28.9-31.0 dBm, corresponding to a saturated power-added efficiency (PAE) of 25.2%-33.5%, and a 6 dB output power back-off PAE of 15.5%-19.8%. Compared with state-of-the-art similar frequency-band GaN Doherty power amplifiers, the proposed design exhibits a maximum fractional bandwidth of 31.6%, highest small-signal gain and saturated PAE, high saturated output power and 6-dB back-off PAE. Furthermore, it features the smallest chip area among reported three-stage DPA chips. Conclusions This paper presents an ultra-wideband enhanced active load modulation method, which achieves multi-frequency impedance tuning and thus realizes sufficient active load modulation throughout the entire working frequency band. At the same time, a novel ultra-wideband phase compensation unequal power distribution network is proposed, significantly reducing the chip area. To verify the proposed method, a millimeter-wave ultra-wideband high-efficiency Doherty power amplifier chip was fabricated using a 0.15-μm GaN process. Measurement results show that in the wideband range of 24 to 33 GHz, the small-signal gain is 21.8 to 23.8 dB, and the saturated output power is 28.9 to 31.0 dBm. The corresponding saturated PAE is 25.2% to 33.5%, and the 6 dB back-off PAE is 15.5% to 19.8%. Compared with the reported GaN Doherty power amplifiers in similar frequency bands, this paper achieves a maximum relative bandwidth of 31.6%, demonstrating excellent performance, including high small-signal gain, excellent saturated PAE, excellent saturated output power, and 6 dB back-off PAE. Moreover, it has the smallest chip area among the reported 2-3-stage DPA MMICs. These measurement results validate the effectiveness of the proposed technology and demonstrate the strong application potential of this chip in millimeter-wave satellite communication transmission systems. -
Key words:
- Satellite Communications /
- Millimeter Wave /
- Doherty Power Amplifier /
- Ultra-Wideband /
- High Efficiency
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表 1 与目前报道的毫米波GaN DPA MMIC性能对比表
参考
文献频率
(GHz)相对带宽(%) 级数 Psat
(dBm)增益
(dB)PAE(%)
@PsatPAE(%)@
6dB PBO芯片面积(mm2) 年份 所采用工艺 [11] 24-28 15.4 2 36.8-38.1 16.4-20 29.7-36.8 18.6-32a 7.44 2024 0.15um GaN [15] 24-28 15.4 2 35.4-36 14.9-19.7 27.8-36.8 18.1-30.1 5.95 2022 0.15um GaN [16] 24-30 22.2 2 31.6-32.7 9.8-14.9 20-27.6 18.2-22.4 6.3 2025 0.12um GaN [17] 24-29 18.9 2 34.8-36.1 15.7-19.5 25-31.7 19-24.8 5.32 2024 0.15um GaN [18] 28-29.5 5.2 3 34.6 13 24 21 11.78 2024 0.15um GaN [19] 29.1 - 1 30 9 44 28 5.38 2022 0.15um GaN 本文 24-33 31.6 3 28.9-31.0 21.8-23.8 25.2-33.5 15.5-19.8 4.05 2026 0.15um GaN 注:a:8dB回退效率 -
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