A proposed method for achieving active load-modulation technique without using a quarter-wavelength transmission line is discussed and evaluated. The theoretical analysis shows that the active load-modulation can be achieved without using a quarter-wavelength line, where the main amplifier sees a low impedance when the input signal level is low, and this impedance increases in proportion to the amount of current contributed from the peaking amplifier. The peaking amplifier sees an impedance decreasing from infinity to the normalized impedance. To validate the method, a circuit was designed, simulated and fabricated using two symmetrical gallium nitride (GaN) transistors (6 W) to achieve a peak power of 12 W and 6 dB output back-off efficiency. The design operates with 400 MHz bandwidth at 3.6 GHz and showed an average efficiency of 50% at 6 dB back-off and an efficiency of 75% at peak power. The designed circuit was tested with CW and modulated signals, the amplifier showed an Adjacent Channel Power Ratio (ACPR) of 31–35.5 dB when tested with a wideband code division multiple access signal of 6 dB peak-average-power ratio (PAPR) at 35.5 dBm average power. Additional 20 dB of linearity improvement was achieved after adding a lineariser.

中文翻译：

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不使用四分之一波长传输线的负载调制技术

讨论并评估了一种无需使用四分之一波长传输线即可实现有源负载调制技术的方法。理论分析表明，无需使用四分之一波长线就可以实现有源负载调制，在四分之一波长线中，当输入信号电平较低时，主放大器会看到低阻抗，并且该阻抗与电流贡献的比例成正比。峰值放大器。峰值放大器的阻抗会从无穷大下降到归一化阻抗。为了验证该方法，使用两个对称的氮化镓（GaN）晶体管（6 W）设计，仿真和制造了电路，以实现12 W的峰值功率和6 dB的输出补偿效率。该设计在3的400 MHz带宽下运行。频率为6 GHz，在6 dB后退时显示出50％的平均效率，在峰值功率下显示为75％的效率。设计的电路用CW和调制信号进行了测试，在使用6 dB峰均功率比（PAPR）的宽带码分多址信号进行测试时，该放大器的邻道功率比（ACPR）为31–35.5 dB 35.5 dBm平均功率。添加线性化器后，线性度进一步提高了20 dB。