Hybrid continuous-discrete-time multi-bit delta-sigma A/D converters with auto-ranging algorithm

In wireless portable applications, a large part of the signal processing is performed in the digital domain. Digital circuits show many advantages. The power consumption and fabrication costs are low even for high levels of complexity. A well established and highly automated design flow allows one to benefit from the constant progress in CMOS technologies. Moreover, digital circuits offer robust and programmable signal processing means and need no external components. Hence, the trend in consumer electronics is to further reduce the part of analog signal processing in the receiver chain of wireless transceivers. Consequently, analog-to-digital converters with higher resolutions and bandwidths are constantly required. The ultimate goal is the direct digitization of radio frequency signals, where the conversion would be performed immediately after the front-end amplifier. ΔΣ-modulation-based converters have proved to be the most suitable to achieve the required performance. Switched-capacitor implementations have been widely used over the last two decades. However, recent publications and books have shown that continuous-time architectures can achieve the same performance with lower power consumption. Most designs found throughout the literature use a single- or few-bit internal quantizer with a high-order modulation. As a result, in order to achieve the resolutions and bandwidths required today, the sampling frequency must exceed 100MHz. This approach leads to non-negligible power consumption in the clock generation. Moreover, the presence of such fast squared signals is not suitable for a system-on-chip comprising radio frequency receivers. In this thesis we propose a low-power strategy relying on a large number of internal levels rather than on a high sampling frequency or modulation order. Besides, a hybrid continuous-discrete-time approach is used to take advantage of the accuracy of switched-capacitor circuits and the low power consumption of continuous-time implementation. The sensitivity to clock jitter brought about by the continuous-time stage is reduced by the use of a large number of levels. An auto-ranging algorithm is developed in this thesis to overcome the limitation of a large-size quantizer under low-voltage supply. Finally, the strategy is applied to a design example addressing typical specifications for a Bluetooth receiver with direct conversion

Systems Engineering for Silicon Photonic Devices

The increasing integration of digital information with our daily lives has led to the rise of big data, cloud computing, and the internet of things. The growth in these categories will lead to an exponential increase in the required capacity for data centers and high performance computation. Meanwhile, due to bottlenecks in data access caused by the limited energy and bandwidth scalability of electrical interconnects, computational speedup can no longer scale with demand. A better solution is necessary in order to increase computational performance and reduce the carbon footprint of our digital future. People have long thought of photonic interconnects, which can offer higher bandwidth, greater energy efficiency, and orders-of-magnitude distance scalability compared to electrical interconnects, as a solution to the data access bottleneck in chip, board, and datacenter scale networks. Over the past three decades we have seen impressive growth of photonic technology from theoretical predictions to high-performance commercially available devices. However, the dream of an all-optical interconnection network for use in CPU, Memory, and rack-to-rack datacenter interconnects is not yet realized. Many challenges and obstacles still have to be addressed. This work investigates these challenges and describe some of the ways to overcome them. First we will first examine the pattern sensitivity of microring modulators, which are likely to be found as the first element in an optical interconnect. My work will illustrate the advantage of using depletion mode modulators compared to injection mode modulators as the number of consecutive symbols in the data pattern increases. Next we will look at the problem of thermal initialization for microring demultiplexers near the output of the optical interconnect. My work demonstrates the fastest achieved initialization speed to-date for a microring based demultiplexer. I will also explore an thermal initialization and control method for microrings based on temperature measurement using a pn-junction. Finally, we will look at how to control and initialize microring and MZI based optical switch fabrics, which is the second element found in a optical interconnect. Work here will show the possibility of switching high-speed WDM datastreams through microring based switches, as well as methods to deal with the complexities inherent in control and initialization of high-radix switch topologies. Through these demonstrations I hope to show that the challenges facing optical interconnects, although very real, are surmountable using reasonable engineering efforts

A Novel Implementation of Dithered Digital Delta-Sigma Modulators via Bus-Splitting

Abstract—This paper presents a design methodology for dithered bus-splitting Multi stAge noise SHaping (MASH) dig-ital delta-sigma modulators (DDSMs). Rules for selecting the appropriate wordlengths of the constituent DDSMs are derived which ensure that the spectral performance of the bus-splitting architecture is comparable to that of the conventional design but with less hardware. Behavioral simulations are presented which confirm the theoretical predictions. I

Sixteenth International Laser Radar Conference, part 2

Given here are extended abstracts of papers presented at the 16th International Laser Radar Conference, held in Cambridge, Massachusetts, July 20-24, 1992. Topics discussed include the Mt. Pinatubo volcanic dust laser observations, global change, ozone measurements, Earth mesospheric measurements, wind measurements, imaging, ranging, water vapor measurements, and laser devices and technology

Proceedings of the Third International Mobile Satellite Conference (IMSC 1993)

Satellite-based mobile communications systems provide voice and data communications to users over a vast geographic area. The users may communicate via mobile or hand-held terminals, which may also provide access to terrestrial cellular communications services. While the first and second International Mobile Satellite Conferences (IMSC) mostly concentrated on technical advances, this Third IMSC also focuses on the increasing worldwide commercial activities in Mobile Satellite Services. Because of the large service areas provided by such systems, it is important to consider political and regulatory issues in addition to technical and user requirements issues. Topics covered include: the direct broadcast of audio programming from satellites; spacecraft technology; regulatory and policy considerations; advanced system concepts and analysis; propagation; and user requirements and applications