CCSS: Switched Capacitor Power Amplifiers for Digital MIMO Transmitters

提高数据传输速率以支持高清视频内容和提高无线的可用性的愿望促使数据服务提供商为用户的移动设备和由通信提供商操作的定点基站之间的每条通信链路使用多于一个天线。这需要复杂的波束控制电路和系统，能够适当地引导来自每个天线的信号，并形成优化无线数据传输的通信波束。当前的电路架构依赖于高度线性的发送器和接收器电路，这在其能量使用方面效率低下。这项研究的目标是引入新的、高能效的发射机/放大器架构，这些架构可以很容易地与波束控制电路集成。当用于移动设备时，这种电路将使电池寿命更长，并且由于效率提高，从电网中消耗的能量将更少。将开发的理论和技术将使工程师和研究人员能够设计更高效的无线传输系统，以更高的数据传输速率运行。除了与该提案相关的科学和工程成果外，教育目标还将寻求在中学教育水平上教育STEM学生，并鼓励他们进入STEM领域，并将重点放在更有效地利用能源等主题上。这将通过课程开发、指导本地中学生，以及在大专教育的早期阶段让本科生参与研究来实现。这项建议的目的是提高数字开关电容功率放大器(SCPA)的分辨率。为了使这些功率放大器能够在无线系统中实际使用，必须提高这些功率放大器的分辨率，因为由于信号量化而产生的带外噪声限制了它们在无线系统中的部署。目前，SCPA已被限制为小于8比特的幅度量化。SCPA不仅需要额外的分辨率来将带外噪声降低到足够的水平，还需要额外的幅度控制来实现更好的光束聚焦。其他数字功率放大器已经达到了更高的分辨率。然而，它们不是线性的；因此它们必须使用数字预失真来校正非线性。拟议的研究将解决目前使用以下技术提高SCPA分辨率方面的几个限制：(1)分离阵列技术，其允许更高的分辨率，并在微线CMOS工艺中实现电容元件的实际电容大小；(2)C-2C阵列技术，以改善阵列中电容的匹配，将改善SCPA的线性度，同时减少对片上硬件解码的需要；(3)数字信号处理技术，如动态范围缩小和数字预失真，增强更高分辨率阵列的操作；(4)多输入多输出(MIMO)系统集成与验证。实验的设计和发现可以为在MIMO系统中部署此类数字功率放大器提供相关指导，并进一步使数字接口更接近天线，从而为可部署的软件定义无线电提供有前景的解决方案。

The desire for increases in data transmission rates to support hi-definition video content and increased availability of wireless has pushed data service providers to use more than one antenna for each communication link between a user's mobile device and the fixed point base station operated by the communications provider. This requires complex circuits and systems for beam-steering that can appropriately direct the signal from each antenna and form a communications beam that optimizes wireless data transmission. Current circuit architectures rely on highly linear transmitter and receiver circuitry that is inefficient in its energy usage. The goal of this research is to introduce new, highly energy efficient transmitter/amplifier architectures that are easily integrated with the beam-steering circuitry. Such circuits will enable longer battery lifetimes when used for mobile devices and will draw less energy from the electric grid due to increased efficiency. The theories and techniques that will be developed will enable engineers and researchers to design more efficient wireless transmission systems that operate with much higher data transmission rates. In addition to the scientific and engineering outcomes associated with the proposal, the educational objectives will seek to educate STEM students at the secondary education level and encourage them to enter into STEM fields and focus on topics such as using energy more efficiently. This will be accomplished by curriculum development, mentoring local secondary students and also incorporating undergraduate students into research at early stages in their post-secondary education.The objective of this proposal is to improve the resolution available in digital switched-capacitor power amplifiers (SCPAs). Increase in the resolution of these power amplifiers is necessary to enable their practical use in wireless systems, as the out-of-band noise, owing to signal quantization, limits their deployment in wireless systems. Presently SCPAs have been limited to amplitude quantization of less than eight bits. Not only does the SCPA need additional resolution to drive the out-of-band noise down to sufficient levels, additional amplitude control is needed to allow better focusing of the beam. Other digital power amplifiers have achieved higher resolution. However, they are not as linear; hence they must use digital pre-distortion for correction of the nonlinearity. The proposed research will address several of the current limitations in increasing the resolution of the SCPA using techniques that include: (1) Split-array techniques that allow higher resolution with practical capacitor sizing of capacitive elements in fine-line CMOS processes; (2) C-2C array techniques to improve the matching of the capacitors in the array that will improve the SCPA's linearity while reducing the need for on-chip hardware decoding; (3) Digital signal processing techniques such as dynamic range reduction and digital pre-distortion, that enhance the operation of the higher resolution arrays; and (4) Multiple-input, multiple-output (MIMO) system integration and validation. The designs and findings from the experiment can provide relevant guidelines for deployment of such digital power amplifiers in MIMO systems and further move the digital interface closer to the antenna, allowing promising solutions toward deployable software defined radios.