Direct RF-to-Digital Data Converters Using Time-Varying Circuits

应用程序要求我们的便携式设备提供越来越多的各种无线通信，如蜂窝，WiFi， GPS，蓝牙和专有通信，允许可穿戴和可植入设备与智能手机有效连接。因此，希望有一个紧凑的单一通用收音机，类似于迪克特雷西手表收音机，以无缝地处理这种通信的众多。不幸的是，这样一个通用的无线电已经被证明是非常困难的，特别是用于便携式通信设备。该项目旨在开发这种通用无线电的核心技术：一种模数转换器，在消耗低电池电量的情况下，精确地将入射到天线上的大量电磁信号频谱数字化。该技术将使无线电硬件能够在方便的软件控制下重新配置。此外，它将启用所谓的认知无线电，通过动态识别和机会地使用空闲频段来增加稀缺电磁频谱的利用率。通用无线电和认知无线电对该国无线连接的进一步发展至关重要。开发的技术可用于国防电子和医疗设备，其中电磁频谱传感和感知对于成像和安全应用非常重要。除了技术影响外，拟议的研究活动将为加州大学洛杉矶分校的本科生和研究生提供信号处理和电子电路设计技术之间强大相互作用的宝贵培训。这种跨学科的培训将帮助工程师更好地解决电气工程中许多不断变化的挑战。该项目的目标是开发电路和信号处理技术，以实现宽带，高分辨率，模数转换器（adc），可以放置在接收器的天线处或非常靠近天线处。该方法采用多速率滤波器组概念和时变电路。简而言之，一组由特别选择的周期性时变电路元件制成的模拟滤波器将被用于将RF信号信道化到单独但重叠的频带中，然后使用一组较慢的adc将其数字化。一组数字滤波器将智能地组合ADC输出，忠实地重建原始信号。原型集成电路将被设计、制造和测试，以验证所提议的直接射频到数字转换器的可行性和实用性，并展示创纪录的ADC带宽和分辨率组合。这个项目的智力价值是三重的。首先，它将开发一种新的频率信道化ADC方法，与传统的时间交错ADC方法相比，该方法对电路失配不太敏感，并且具有宽松的动态范围要求。其次，时变电路技术彻底改变了传统的线性和时不变电路原理，将带来显著的性能和功耗优势。时变方法可以实现对频率信道化滤波器的非常高的线性度和精度控制，从而解决所有先前使用一组模拟预滤波器的ADC方法的中心问题。最后，所提出的研究表明集成电路设计与信号处理理论之间的紧密耦合对于解决集成电路设计中的突出问题变得越来越重要。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Applications demand our portable devices to provide an ever-increasing number of diverse wireless communications such as cellular, WiFi, GPS, Bluetooth, and proprietary communications that allow wearable and implantable devices to link efficiently with a smartphone. As such, it is desirable to have a compact single universal radio, similar to a Dick Tracy wristwatch radio, to seamlessly handle the multitude of such communications. Unfortunately, such a universal radio has proven notoriously hard to build, especially for use in a portable communications device. This project aims to develop the technology for the central piece of this universal radio: an analog-to-digital converter that precisely digitizes a large swath of the electromagnetic signal spectrum incident on an antenna while consuming low battery power. The technology will enable radio hardware that can be reconfigured under convenient software control. In addition, it will enable the so-called cognitive radios that increase the utilization of scarce electromagnetic spectrum by dynamically identifying and opportunistically using vacant frequency bands. Both universal and cognitive radios are critically important to the further advancement of wireless connectivity in the country. The developed technology can find use in defense electronics and medical equipment where electromagnetic spectrum sensing and awareness is important for imaging and security applications. In addition to the technical impact, the proposed research activities will provide the diverse undergraduate and graduate students at the University of California, Los Angeles, with invaluable training in the strong interplay between signal processing and electronic circuit design techniques. Such cross-disciplinary training will help engineers better tackle many of the evolving challenges in electrical engineering.The objective of this project is to develop circuit and signal processing techniques to enable wide bandwidth, high resolution, analog-to-digital converters (ADCs) that can be placed at, or very close to, the antenna in a receiver. The proposed approach employs multi-rate filter-bank concepts and time-varying circuits. In a nutshell, a bank of analog filters, made of specially chosen, periodically time-varying circuit components, will be employed to channelize the RF signal into individual, but overlapping, frequency bands that are then digitized using a bank of slower ADCs. A bank of digital filters will intelligently combine the ADC outputs to faithfully reconstruct the original signal. Prototype integrated circuits will be designed, fabricated, and tested to verify the feasibility and utility of the proposed direct RF-to-digital converters and demonstrate record-setting ADC bandwidth and resolution combinations. The intellectual merits of this project are three-fold. Foremost, it will develop a new frequency-channelization ADC approach that is less sensitive to circuit mismatch and has relaxed dynamic range requirements as compared to the conventional time-interleaved ADC approach. Secondly, the time-varying circuit technique, which is a radical and beneficial departure from the conventional principle of making circuits linear and time-invariant, will lead to significant performance and power consumption benefits. The time-varying approach enables very high linearity and precision control of the frequency channelization filter to solve the central problem of all prior ADC approaches that use a bank of analog pre-filters. Finally, the proposed research represents a very tight coupling between integrated circuit design and signal processing theory that is becoming increasingly essential to solve the outstanding problems in integrated circuit design.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.