Asymmetrical Load Modulated Balanced Amplifier With Continuum of Modulation Ratio and Dual-Octave Bandwidth
Asymmetrical Load Modulated Balanced Amplifier With Continuum of Modulation Ratio and Dual-Octave Bandwidth
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DOI：
10.1109/tmtt.2020.3014616
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发表时间：
2021-01
影响因子：
4.3
通讯作者：
Yuchen Cao;Haifeng Lyu;Kenle Chen
中科院分区：
文献类型：
--
作者：
Yuchen Cao;Haifeng Lyu;Kenle Chen
提出了一种新型的负载调制功率放大器结构--非对称负载调制平衡放大器。首次发现通过平衡拓扑结构中两个子放大器（BA 1和BA 2）的对称性偏移，LMBA的控制放大器（CA）可以设计成任意负载调制比（LM）。严格的分析推导揭示了统一的正交耦合器为基础的LM PA理论，其中包括最近报道的LMBA在这个广义的框架内。通过非对称BA 1和BA 2（峰化）和CA（载波）的伪Doherty（PD）偏置结合适当的幅度和相位控制，可以独立地实现三个放大器的最佳LM行为，从而扩展功率回退范围和超宽RF带宽。重要的是，CA的LM有效地减轻了施加在对称PD-LMBA上的过驱动问题，从而增强了整体可靠性和线性度。基于所提出的理论，一个RF输入PD-ALMBA的设计和实现使用商业GaN晶体管。所开发的原型实验表明，从0.55到2.2 GHz的双倍频程带宽，这是有史以来最宽的带宽负载调制功率放大器。在设计带宽内，峰值输出功率的效率为49-82%，10 dB OBO的效率为40-64%。当受到具有10.5 dB峰均功率比（PAPR）的20 MHz长期演进（LTE）信号的激励时，在平均输出功率约为33 dBm的情况下，在整个带宽上测量到47-63%的平均效率。
This article presents a new load-modulation power amplifier (PA) architecture—asymmetrical load-modulated balanced amplifier (ALMBA). It is for the first time discovered that the control amplifier (CA) of LMBA can be designed with arbitrary load modulation (LM) ratio by offsetting the symmetry of two sub-amplifiers (BA1 and BA2) in the balanced topology. The rigorous analytical derivation reveals a unification of the quadrature-coupler-based LM PA theory, which inclusively covers the recently reported LMBA within this generalized framework. Through pseudo-Doherty (PD) biasing of the asymmetric BA1 & BA2 (peaking) and the CA (carrier) combined with proper amplitude and phase controls, the optimal LM behaviors of three amplifiers can be achieved independently overextended power back-off range and ultrawide RF bandwidth. Importantly, the LM of CA effectively mitigates the over-driving issue imposed on symmetrical PD-LMBA, leading to enhanced overall reliability and linearity. Based on the proposed theory, an RF-input PD-ALMBA is designed and implemented using commercial GaN transistors. The developed prototype experimentally demonstrates dual-octave bandwidth from 0.55 to 2.2 GHz, which is the widest bandwidth ever reported for load-modulation PAs. The measurement exhibits an efficiency of 49–82% for peak output power and 40–64% for 10-dB OBO within the design bandwidth. When stimulated by a 20-MHz long-term evolution (LTE) signal with 10.5-dB peak to average power ratio (PAPR), an average efficiency of 47–63% is measured over the entire bandwidth at an average output power around 33 dBm.