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Delta-Sigma-Based Transmitters: Advantages and Disadvantages

机译：基于Delta-Sigma的变送器：优点和缺点

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Power efficiency is one of the most important parameters in designing communication systems, especially battery operated mobile terminals. In a typical transceiver, most of the power is dissipated in the power amplifier (PA) and consequently, it is very important to obtain the maximum efficiency from the PA. A PA operating in Class AB or B is at its maximum efficiency when it is driven by its maximum allowable input power [1]. In practice, the input signal of the PA usually has a varying envelope, and to avoid distortion the PA should not be driven to more than its maximum input saturating power. Unfortunately, this peak power of the input signal happens at very short periods, and most of the time the signal power is around its average power, which is much smaller than its peak power, meaning that, often, the PA works at much lower efficiencies than its maximum efficiency. The power difference is defined as the peak to average power ratio (PAPR) of the signal. For example, for a signal with 12 dB PAPR, a Class B PA would be driven with 12 dB power back-off from its peak input power, and at this power back-off, the efficiency of the PA will degrade from 78.5% to around 20% [1]. Unfortunately, by moving to high throughput modulation schemes, for example, quadrature amplitude modulations (QAMs) such as 16-QAM and 64-QAM mean that more envelope variation is needed to encode the information, and, consequently, lower efficiency is achieved.
机译：在设计通信系统，尤其是电池供电的移动终端时，功率效率是最重要的参数之一。在典型的收发器中，大部分功率消耗在功率放大器（PA）中，因此，从PA获得最大效率非常重要。由AB或B类运行的PA由最大允许输入功率驱动时，效率最高。[1]。实际上，PA的输入信号通常具有变化的包络，并且为避免失真，不应将PA驱动至超过其最大输入饱和功率。不幸的是，输入信号的峰值功率发生在非常短的时间内，并且在大多数情况下，信号功率都在其平均功率附近，该平均功率远小于其峰值功率，这意味着功率放大器通常工作时的效率要低得多。超过其最大效率。功率差定义为信号的峰均功率比（PAPR）。例如，对于具有12 dB PAPR的信号，将以其峰值输入功率从12 dB功率退避来驱动B类PA，在这种功率退避下，PA的效率将从78.5％降低至约20％[1]。不幸的是，例如，通过转向高吞吐量调制方案，诸如16-QAM和64-QAM之类的正交幅度调制（QAM）意味着需要更多的包络变化来编码信息，因此，实现了较低的效率。

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