Research on Ka-band Enhanced Active Load Modulation Ultra-wideband High-efficiency Doherty Power Amplifier

YANG Lin; YAN Chengyu; WANG Yanping; ZHANG Ming; WANG Baozhu; HAN Qi; HE Yuhang; HOU Weimin; LI Kang

doi:10.11999/JEIT260514

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YANG Lin, YAN Chengyu, WANG Yanping, ZHANG Ming, WANG Baozhu, HAN Qi, HE Yuhang, HOU Weimin, LI Kang. Research on Ka-band Enhanced Active Load Modulation Ultra-wideband High-efficiency Doherty Power Amplifier[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT260514

Citation:

YANG Lin, YAN Chengyu, WANG Yanping, ZHANG Ming, WANG Baozhu, HAN Qi, HE Yuhang, HOU Weimin, LI Kang. Research on Ka-band Enhanced Active Load Modulation Ultra-wideband High-efficiency Doherty Power Amplifier[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT260514

Citation:

YANG Lin, YAN Chengyu, WANG Yanping, ZHANG Ming, WANG Baozhu, HAN Qi, HE Yuhang, HOU Weimin, LI Kang. Research on Ka-band Enhanced Active Load Modulation Ultra-wideband High-efficiency Doherty Power Amplifier[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT260514

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Research on Ka-band Enhanced Active Load Modulation Ultra-wideband High-efficiency Doherty Power Amplifier

doi: 10.11999/JEIT260514 cstr: 32379.14.JEIT260514

1.
School of Information Science and Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, China
2.
School of Artificial Intelligence and Computer Science, North China University of Technology, Beijing 100144, China
3.
School of Integrated Circuit, Xidian University, Xi’an 710003, China

Funds: The National Natural Science Foundation of China (62441401), TThe National Key Research and Development Program of China (2022YFB4400400), The National Key Laboratory of Basic Scientific Research for Innovation Fund (IFN20230113), Major Science and Technology Support Project of Hebei Province (No.24290201Z), Hebei Natural Science Foundation (F2024208020), Science and Technology Project of Hebei Education Department (BJK2024089)

Received Date: 2026-04-27
Accepted Date: 2026-06-24
Rev Recd Date: 2026-06-21

Available Online: 2026-07-02

Abstract

Abstract

Objective The Ka-band has become a key frequency band for satellite communications, placing stringent requirements on the millimeter-wave power amplifier, a core component of the transmitter, to provide high efficiency, compact size, and broadband operation. To maximize spectral efficiency, millimeter-wave satellite communication signals typically exhibit a high Peak-to-Average Power Ratio (PAPR), making high back-off efficiency particularly important. Although the Doherty Power Amplifier (DPA) is widely adopted because of its high efficiency under power back-off conditions, its operating bandwidth is inherently limited. In addition, both saturated efficiency and back-off efficiency degrade substantially at millimeter-wave frequencies. Therefore, extending the operating bandwidth while maintaining high efficiency remains a major challenge for millimeter-wave DPAs used in satellite communication transmitters. Methods An ultra-wideband enhanced active load modulation technique is proposed to overcome the trade-off between bandwidth and back-off efficiency in DPAs. The proposed method achieves optimal load impedance modulation for both the carrier and peaking amplifiers over an ultra-wide frequency range by introducing an Impedance Tunable Bias Network (ITBN) and a dual-drive impedance control mechanism. These techniques improve load modulation while extending the load modulation bandwidth, thereby enhancing both efficiency and bandwidth in the millimeter-wave DPA architecture. Furthermore, a broadband phase-compensation technique is integrated into an unequal power division network to achieve sufficient load modulation across the entire operating band while accurately compensating for the phase difference between the carrier and peaking paths. The proposed ultra-wideband phase-compensated power division network further extends the high-efficiency operating bandwidth while reducing the chip area. Results and Discussions To validate the proposed method, a millimeter-wave ultra-wideband high-efficiency DPA was designed and fabricated using a 0.15-mm GaN process. Across the 24～33 GHz frequency band, corresponding to a fractional bandwidth of 31.6%, the fabricated chip achieves a small-signal gain of 21.8～23.8 dB with a gain flatness of ±1 dB. The measured saturated output power is 28.9～31.0 dBm, with a Power-Added Efficiency (PAE) of 25.2%～33.5% at saturation and a 6 dB back-off PAE of 15.5%～19.8%. Compared with previously reported GaN DPAs operating over similar frequency bands, the proposed design achieves the highest reported small-signal gain and saturated PAE while maintaining high saturated output power and high 6 dB back-off PAE. Furthermore, it occupies the smallest chip area among reported three-stage DPA MMICs. Conclusions An ultra-wideband enhanced active load modulation method is proposed to achieve sufficient active load modulation through multi-frequency impedance tuning across the entire operating band. A novel ultra-wideband phase-compensated unequal power division network is also proposed to reduce the chip area while maintaining accurate phase compensation. To validate the proposed method, a millimeter-wave ultra-wideband high-efficiency DPA was fabricated using a 0.15-mm GaN process. Measurement results demonstrate that, over the 24～33 GHz frequency band, the fabricated chip achieves a small-signal gain of 21.8～23.8 dB, a saturated output power of 28.9～31.0 dBm, a saturated PAE of 25.2%～33.5%, and a 6 dB back-off PAE of 15.5%～19.8%. Compared with previously reported GaN DPAs operating in similar frequency bands, the proposed design achieves a maximum fractional bandwidth of 31.6%, the highest reported small-signal gain and saturated PAE, high saturated output power, and high 6 dB back-off PAE, while occupying the smallest chip area among reported two- and three-stage DPA MMICs. These measurement results validate the proposed method and demonstrate its strong potential for millimeter-wave satellite communication transmitters.
- Satellite communications,
- Millimeter wave,
- Doherty Power Amplifier (DPA),
- Ultra-wideband,
- High efficiency

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References(19)

References

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