SBIR Phase I: Modified Doherty Transmit Architecture Employing Digital Signal Synthesis for Wideband RF Communication

该小型企业创新研究(SBIR)第一阶段项目旨在展示一种能够为无线基础设施应用提供突破性性能的射频(RF)发射机。这种高度数字化的发射机的三项主要创新预计将带来显著的性能提升。首先，基于Doherty功率放大器(PA)，提出了一种独特的射频驱动信号最佳数字合成方法，不需要模拟上变频、功率分割和相位调整。数字信号以改进的偏置驱动Doherty PA，实现了比传统设计更高的效率。其次，通过直接预失真数字化的射频波形，在宽带(BW)上进一步提高了效率和线性度。第三，介绍了一种模块化的功率放大器实现方案，该方案可自适应地重新配置，以在负载变化的情况下优化整体功率效率。提出的设计目标是：宽带宽(100 MHz)、可编程载波频率(2.3-2.8 GHz)、高线性度(优于-65dBc)、高输出功率(200W)和优异的平均效率(10dB退避时为60%)。分析表明，与传统的功率放大器相比，最大平均功率的平均效率提高了10%以上，平均功率后退6db的平均效率提高了100%，输出功率和平均功率增益分别提高了11%和4倍。这个项目的广泛影响/商业潜力是相当大的。无线网络运营商长期以来一直要求射频发射机提供更宽的带宽、更高的功率效率、紧凑的尺寸和更高的可重配性，以便以合理的成本向4G演进。传统的发射机不能同时满足这些要求。凭借开创性的性能，建议的技术将是插入下一代4G基站的理想候选。这项工作的商业化将大大节省网络运营商的运营和资本支出，从而以更小、更少和更美观的基站实现经济高效的4G部署。能源消耗的减少也符合绿色技术的未来路线图。将产品插入无线市场有几种选择，包括：独立开发完整的基站产品，与现有的无线基站供应商建立伙伴关系，以及向外部方授权发明。建议的研究将增加对功率放大器非线性的理解，特别是由于本征器件的特性，并展示混合信号的潜力？实现射频发射机的方法，其中快速发展的数字电路的速度和复杂性极大地提高了传统模拟射频系统的性能。

This Small Business Innovation Research (SBIR) Phase I project proposes to demonstrate a Radio Frequency (RF) transmitter capable of groundbreaking performance for wireless infrastructure applications. Significant performance gains are expected from three main innovations in this highly-digital transmitter. First, building on the Doherty Power Amplifier (PA), a unique method of optimal digital synthesis of the RF drive signals is proposed; no analog upconversion, power-split and phase adjustment are needed. Digital signals drive a Doherty PA with modified bias, achieving higher efficiency than conventional designs. Second, efficiency and linearity are further improved over wide bandwidth (BW) by predistorting the digitized RF waveform directly. Third, a modular PA implementation is introduced, which is adaptively reconfigured to optimize the overall power efficiency with varying load. The design goals of the proposed work are: wide BW (100MHz), widely programmable carrier frequency (2.3-2.8GHz), high linearity (better than -65dBc), high output power (200W) and excellent average efficiency (60% at 10dB backoff). Analysis comparing the proposed PA to a conventional design shows average efficiency improvements of over 10% for maximum average power and up to 100% for 6dB backed off average power; the output power and average power gain are enhanced by 11% and 4× respectively. The broader impact/commercial potential of this project is considerable. Wireless network operators have long been demanding RF transmitters offering wider BW, better power efficiency, compact size and increased re-configurability to evolve their networks towards 4G at reasonable cost. Conventional transmitters cannot these requirements simultaneously. With groundbreaking performance, the proposed technology would be an ideal candidate for insertion into next generation 4G basestations. Commercialization of this work would result in significant savings in operational and capital expense for network operators, thereby enabling cost-effective 4G deployment with smaller, fewer and more aesthetic basestations. Reduction in energy consumption is also in line with the future roadmap of ?green technology?. Several options exist for product insertion into the wireless marketplace including: independent development of a complete basestation product, partnership with an established supplier of wireless basestations and licensing of inventions to external parties. The proposed research will increase understanding of PA nonlinearities, especially due to intrinsic device properties, and demonstrate the potential of a ?mixed signal? approach to realizing RF transmitters, wherein the rapidly advancing speed and complexity of digital circuits greatly improves the performance of traditionally analog RF systems.