Dynamic drive for radio frequency power amplifiers with wideband active load modulation

本项目的目标是开展宽带有源负载调制射频功率放大器动态驱动先进技术的基础研究。与传统的单轨功率放大器不同，具有有源负载调制的双输入功率放大器架构不受单一、独特的驱动功能的限制。它们的输入矢量跨越多维负载调制空间，理论上，该空间包含无限多个驱动函数，这些函数都导致相同的输出信号，但分别以不同的瞬时效率和不同的带宽要求。因此，所提出的驱动技术的目标是最大化放大器系统的平均效率，同时满足通信标准施加的线性度要求，并将预失真带宽保持在硬件施加的限制内。动态驱动函数的概念源于申请人以前的工作，该工作表明，在宽带工作下，具有有源负载调制的双输入功率放大器的最大有效驱动函数在其导数中表现出多个特征的不连续性。由于可用的预失真带宽不可避免地是有限的，如果在整个幅度范围内执行近似，则最大有效驱动函数的逼近效果很差，因此不能充分发挥放大器的效率潜力。另一方面，观察到a)由于信号统计，在整个幅度范围上的近似基本上是不必要的，以及b)不同驱动函数之间的转换不会增加预失真带宽，只要它发生在低功率区域内，在有源负载调制开始之前。这些发现引发了使驱动功能动态地适应各个信号块内的峰值功率的想法，从而平均而言，可以应用产生显著更高的瞬时效率的驱动功能。为了能够实际实施动态驱动技术，应在拟议的研究项目中开发新的预失真模型，以解决目前缺乏真正支持单输入、双输出架构的预失真模型的问题。在此背景下，重要的是指出所提出的动态驱动技术与宽带/多频带预失真的一般问题之间的密切相似之处。由于这种关系，可以假设真正的宽带预失真模型能够在不显著增加其复杂性的情况下结合所提出的驱动函数技术。动态驱动技术的潜力应在拟议的项目中基于申请人所在研究所现有的宽带双输入功率放大器硬件演示器进行验证和演示。

The objective of the project proposed here is to perform fundamental research on advanced techniques for the dynamic drive of radio frequency power amplifiers with wideband active load modulation. Unlike conventional, single-track power amplifiers, dual-input power amplifier architectures with active load modulation are not bound to a single, unique drive function. Their input vectors span a multidimensional load modulation space, which, in theory, contains an infinite number of drive functions that all lead to the same output signal, but at different instantaneous efficiencies and different bandwidth requirements, respectively. Thus, the goal of the proposed drive techniques is to maximize the average efficiency of the amplifier system while meeting the linearity requirements imposed by the communication standard and keeping the predistortion bandwidth within the limits imposed by the hardware. The idea of a dynamic drive function arises from the applicant`s previous work, which has shown that, under wideband operation, the maximum efficient drive function of a dual-input power amplifier with active load modulation exhibits multiple, characteristic discontinuities in its derivative. Since the available predistortion bandwidth is inevitably limited, the maximum efficient drive function can only be approximated poorly if the approximation is performed over the entire amplitude range and thus the amplifiers potential for efficiency cannot be fully exploited. On the other hand, it is observed that a) an approximation over the entire amplitude range is mostly unnecessary, due to signal statistics, and b) a transition between different drive functions does not increase predistortion bandwidth as long as it takes place within the low power region, before the onset of active load modulation. These findings give rise to the idea of dynamically adapting the drive function to the peak power within individual signal blocks, such that, on average, drive functions that produce significantly higher instantaneous efficiencies can be applied. In order to enable a practical implementation of the dynamic drive technique, novel predistortion models shall be developed within the proposed research project, addressing the current lack of predistortion models that genuinely support the single-input, dual-output architecture. In this context, it is important to point out the close similarity between the proposed dynamic drive techniques and the general problem of wideband/multiband predistortion. Due to this relationship, it can be assumed that a truly wideband predistortion model is able to incorporate the proposed drive function technique without significantly increasing its complexity. The potential of the dynamic drive techniques shall be verified and demonstrated within the proposed project based on hardware demonstrators of wideband dual-input power amplifiers which already exist at the applicant`s institute.