基于GaAs技术的两段匹配-相位差补偿网络宽带准非对称Doherty功率放大器设计
A Wideband Quasi-Asymmetric Doherty Power Amplifier with a Two-Section Matching-Phase Difference Compensator Network Design Using GaAs Technology
摘要：
本文采用GaAs0.25 μ mpHEMT工艺，设计了一种无负载调制的准非对称Doherty功率放大器（PA），通过电路设计实现了放大的输出功率回退（OPBO），克服了工艺限制。为了防止功率泄漏在辅助PA（PAaux）由于其极大的关态阻抗，威尔金森功率合成器被添加到输出。此外，输入非对称功分器的设计，以保证没有相当大的功率被输送到主PA（PAmain）在高功率区，使其饱和。提出了一种两段式匹配网络，用于同时补偿主、辅放大路径的相位差。为了控制PAaux相对于扫描功率的显著阻抗变化以及主放大路径和辅助放大路径的不同阻抗轨迹，分析PAaux的偏置和尺寸选择以达到期望的输出功率分布相对于输入功率。这些方法克服了阻抗变化和线性退化。为了实现目标的10%的分数带宽，适当的低质量LC网络被选为匹配网络。仿真结果表明，该结构的微波链路应用的实用性。连续波模拟表明，Doherty功率放大器在7.6-8.4GHz的工作频率范围内，最大输出功率为33 dBm，功率增益为13.5dB，功率增益压缩小于1dB。最大输入功率时的漏极效率为30%，二次谐波和三次谐波的最小功率分别为-140dBm和-130dBm，OPBO为7.5dB。
英文摘要：
In this paper, a quasi-asymmetric Doherty power amplifier (PA) is designed without load modulation using the GaAs 0.25μm pHEMT technology to reach an enlarged output power back-off (OPBO) with circuitry solutions in order to overcome technology restrictions. To prevent power leakage in auxiliary PA (PAaux) due to its extremely large off-state impedance, a Wilkinson power combiner is added to the output. Moreover, an input asymmetric power divider is designed to guarantee that no considerable power is delivered to main PA (PAmain) in the high-power region to make it saturated. A two-section matching network is proposed for PAmain, which simultaneously compensates for phase differences of the main and auxiliary amplification paths. To control the significant impedance variation of PAaux versus sweeping power and the different impedance trajectories of the main and auxiliary amplification paths, the bias and dimension selection of PAaux are analyzed to reach the desired output power profile versus input power. These methods overcome impedance variations and linearity degradation. To achieve the aimed 10% fractional bandwidth, appropriate low-quality LC-networks are selected as matching networks. The simulation results indicate the utility of the proposed structure for microwave link applications. Continuous-wave simulations imply that the Doherty PA has a 33dBm maximum output power and a 13.5dB power gain with less than 1dB power gain compression in the desired frequency range (7.6-8.4GHz). The drain efficiency of 30% at the highest input power, minimum of second and third harmonic powers of -140dBm and -130dBm, respectively, and OPBO of 7.5dB are also obtained.
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