Transimpedance Amplification of Optocoupler Output for High Temperature Applications

When looking to the future of electronics, one characteristic is becoming more lucrative: high temperature capabilities. With the goals of not only becoming more efficient electronically, spatially, and cost-wise, adapting electronics for a high temperature environment can potentially be a route to all three of these goals. Not only does it take away the need for a cooling method, but it can also increase the longevity of a product which can make it even more cost effective. In an effort to contribute to the push for high temperature electronics, the University of Arkansas is developing a high temperature power module for use in various extreme environments. This includes the design of a two-stage transimpedance amplifier (TIA) to take input from an optocoupler and convert it to a useable gate drive signal for amplification. The tradeoffs in creating a TIA must be considered: gain and bandwidth, where a larger bandwidth results in less gain and also becomes more complex as more stages are added. Adding a second stage may increase the speed and gain of the amplifier, but this must also be evaluated with the increase in complexity in cost. So long as the cost is not so much more benefits the entire system as a whole, producing a clean gate drive signal for use at room temperature, it may be beneficial to employ this second stage. This can be adapted into high temperature circuitry for integration into the power module and with additional research, supply the signal required at temperatures up to 250 C

A single-event transient tolerant optical receiver

Fiber optical communication systems have attained significant importance in space applications e.g. Satellites, Space stations, etc. The systems have remarkably lightweight characteristics, less frequency dependent loss, and provide high-speed data transmission in a power-efficient way. Satellites and space stations are exposed to a higher level of radiation due to energetic particles in space. Fiber optical links mainly consist of integrated semiconductor devices. When integrated circuits are exposed to radiation such as in space applications, they are influenced by high-energy ionizing particles. This radiation causes malfunctioning of electronic devices and reduces their life span. It also generates transmission errors which are classified as single-event transients (SETs), single event upsets, and single event latch-up, and also causes total ionization dose effects. This thesis proposes a radiation tolerant (SET tolerant) optical receiver using triple modular redundancy (TMR) in which a conventional receiver is split into three identical sub-receivers in parallel. Majority voting is performed at the outputs after the received analog signal has been thresholded. To investigate the effectiveness of the proposed design, a conventional optical receiver is taken as a reference design, and its performance is compared with the proposed TMR-based radiation tolerant optical receiver. The proposed receiver uses an impedance scaling technique so that its overall power dissipation, gain, and bandwidth are the same as the reference design while providing SET tolerance. The proposed receiver removes SET errors with the limitation that only one subreceiver experiences a SET in a given unit interval. By applying the impedance scaling technique, the proposed receiver is robust to SET errors with no increase in overall power dissipation but at the sensitivity cost of 0.8 dB

Integrated Circuits and Systems for Millimeter-Wave Frequencies

In the first section of this thesis, mm-wave circuit- and system-level solutions for addition of multi-user service to conventional multi-antenna phased array architectures will be introduced. The proposed architecture will enhance the link capacity, co-channel user service and hardware cost compared to conventional solutions. Theory and design of the circuits and system are detailed and comprehensive measurement results are presented verifying the system-level functionality. First section is named A Millimeter-Wave Partially-Overlapped Beamforming-MIMO Receiver: Theory, Design, and Implementation. More specifically, this section presents an analysis and design of a partially-overlapped beamforming-MIMO architecture capable of achieving higher beamforming and spatial multiplexing gains with lower number of elements compared to conventional architectures. As a proof of concept, a 4-element beamforming-MIMO receiver (RX) covering 64-67 GHz frequency band enabling 2-stream concurrent reception is designed and measured. By partitioning the RX elements into two clusters and partially overlapping these clusters to create two 3-element beamformers, both phased-array (coherent beamforming) as well as MIMO (spatial multiplexing) features are simultaneously acquired. 6-bit phase shifters with 360° phase control and 5-bit VGAs with 11 dB range are designed to enable steering of the two RX clusters toward two arbitrary angular locations corresponding to two users. Fabricated in a 130-nm SiGe BiCMOS process, the RX achieves a 30.15 dB maximum direct conversion gain and a 9.8 dB minimum noise figure (NF) across 548 MHz IF bandwidth. S-parameter-based array factor measurements verify spatial filtering of the interference and spatial multiplexing in this RX chip.In the second section of this thesis, energy-efficient ultra-high speed transceiver architectures will be presented. Current high-speed transceivers rely on high-sampling-rate high-resolution power-hungry analog-to-digital converters or digital-to-analog converters at the interface of analog and digital circuitries. However, design of these backend data-converters are extremely power-hungry at very high speeds in a fully-integrated end-to-end scenario (i.e. RF-to-Bits, Bits-to-RF). Novel system-level architectures will be presented that obviate the need for such costly data converters and will significantly relax the complexity of digital signal-processing. The proposed architecture will result in orders of magnitude energy saving at ultra-high speeds. Theory, design, and measurement results of the highest-speed, highly energy-efficient fully-integrated end-to-end transceiver will be discussed in this section. Second section is named A Millimeter-Wave Energy-Efficient Direct-Demodulation Receiver: Theory, Design, and Implementation. More precisely, this section presents the theory, design, and implementation of an 8PSK direct-demodulation receiver based on a novel multi-phase RF-correlation concept. The output of this RF-to-bits receiver architecture is demodulated bits, obviating the need for power-hungry high-speed-resolution data converters. A single-channel 115-135-GHz receiver prototype was fabricated in a 55-nm SiGe BiCMOS process. A max conversion gain of 32 dB and a min noise figure (NF) of 10.3 dB was measured. A data-rate of 36 Gbps was wirelessly measured at 30 cm distance with the received 8PSK signal being directly demodulated on-chip at a bit-error-rate (BER) of 1e-6. The measured receiver sensitivity at this BER is -41.28 dBm. The prototype occupies 2.5 by 3.5 mm squared of die area including PADs and test circuits (2.5 mm squared active area) and consumes a total DC power of 200.25 mW

High gain and bandwidth current-mode amplifiers : study and implementation

Doutoramento em Engenharia ElectrotécnicaEsta tese aborda o problema do projecto de amplificadores com grandes produtos de ganho por largura de banda. A aplicação final considerada consistiu no projecto de amplificadores adequados à recepção de sinais ópticos em sistemas de transmissão ópticos usando o espaço livre. Neste tipo de sistemas as maiores limitações de ganho e largura de banda surgem nos circuitos de entrada. O uso de detectores ópticos com grande área fotosensível é uma necessidade comum neste tipo de sistemas. Estes detectores apresentam grandes capacidades intrínsecas, o que em conjunto com a impedância de entrada apresentada pelo amplificador estabelece sérias restrições no produto do ganho pela largura de banda. As técnicas mais tradicionais para combater este problema recorrem ao uso de amplificadores com retroacção baseados em configurações de transimpedância. Estes amplificadores apresentam baixas impedâncias de entrada devido à acção da retroacção. Contudo, os amplificadores de transimpedância também apresentam uma relação directa entre o ganho e a impedância de entrada. Logo, diminuir a impedância de entrada implica diminuir o ganho. Esta tese propõe duas técnicas novas para combater os problemas referidos. A primeira técnica tem por base uma propriedade fundamental dos amplificadores com retroacção. Em geral, todos os circuitos electrónicos têm tempos de atraso associados, os amplificadores com retroacção não são uma excepção a esta regra. Os tempos de atraso são em geral reconhecidos como elementos instabilizadores neste tipos da amplificadores. Contudo, se usados judiciosamente, este tempos de atraso podem ser explorados como uma forma da aumentar a largura de banda em amplificadores com retroacção. Com base nestas ideias, esta tese apresenta o conceito geral de reatroacção com atraso, como um método de optimização de largura de banda em amplificadores com retroacção. O segundo método baseia-se na destruição da dualidade entre ganho e impedância de entrada existente nos amplificadores de transimpedância. O conceito de adaptação activa em modo de corrente é neste sentido uma forma adequada para separar o detector óptico da entrada do amplificador. De acordo com este conceito, emprega-se um elemento de adaptação em modo de corrente para isolar o detector óptico da entrada do amplificador. Desta forma as tradicionais limitações de ganho e largura de banda podem ser tratadas em separado. Esta tese defende o uso destas técnicas no desenho de amplificadores de transimpedância para sistemas de recepção de sinais ópticos em espaço livre.This thesis addresses the problem of achieving high gain-bandwidth products in amplifiers. The adopted framework consisted on the design of a free-space optical (FSO) front end amplifier able to amplify very small optical signals over large frequency bandwidths. The major gain-bandwidth limitations in FSO front end amplifiers arise due to the input circuitry. Usually, it is necessary to have large area optical detectors in order to maximize signal reception. These detectors have large intrinsic capacitances, which together with the amplifier input impedance poses a severe restriction on the gain-bandwidth product. Traditional techniques to combat this gain-bandwidth limitation resort to feedback amplifiers consisting on transimpedance configurations. These amplifiers have small input impedances due to the feedback action. Nevertheless, transimpedance amplifiers have a direct relation between gain and input impedance. Thus reducing the input impedance usually implies reducing the gain. This thesis advances two new methods suitable to combat the above mentioned problems. The first method is based on a fundamental property of feedback amplifiers. In general, all electronic circuits have associated time delays, and feedback amplifiers are not an exception to this rule. Time delays in feedback amplifiers have been recognized as destabilizing elements. Nevertheless, when used with appropriate care, these delays can be exploited as bandwidth enhancement elements. Based on these ideas, this thesis presents the general concept of delayed feedback, as a bandwidth optimization method suitable for feedback amplifiers. The second method is based on the idea of destroying the impedance-gain duality in transimpedance amplifiers. The concept of active current matching is in this sense a suitable method to detach the optical detector from the transimpedance amplifier input. According to this concept, a current matching device (CMD) is used to convey the signal current sensed by the optical detector, to the amplifier’s input. Using this concept the traditional gainbandwidth limitations can be treated in a separate fashion. This thesis advocates the usage of these techniques for the design of transimpedance amplifiers suited for FSO receiving systems

Fully-Integrated Magnetic-Free Nonreciprocal Components by Breaking Lorentz Reciprocity: from Physics to Applications

Reciprocity is a fundamental physical precept that governs wave propagation in a wide variety of physical domains. The various reciprocity theorems state that the response of a system remains unchanged if the excitation source and the measuring point are interchanged within a medium, and are closely related to the concept of time reversal symmetry in physics. Lorentz reciprocity is a fundamental characteristic of linear, time-invariant electronic and photonic structures with symmetric permittivity and permeability tensors. However, breaking reciprocity enables the realization of nonreciprocal components, such as isolators and circulators, which are critical to electronic, optical and acoustic systems, as well as new functionalities and devices based on novel wave propagation modes. Nonreciprocal components have traditionally relied on magnetic materials such as ferrites that lose reciprocity under the application of an external magnetic field through the Faraday Effect. The need for a magnetic bias limits the applicability of such approaches in small-form-factor Complementary Metal–Oxide–Semiconductor (CMOS)-compatible integrated devices. One of the main features of CMOS technology is the availability of high-speed transistor switches which can be turned ON and OFF, modulating the conductance of the medium. In this dissertation, a novel approach to break Lorentz reciprocity is presented based on staggered commutation in Linear Periodically-Time-Varying (LPTV) circuits. We have demonstrated the world’s first CMOS passive magnetic-free nonreciprocal circulator through spatio-temporal conductivity modulation. Since conductivity in semiconductors can be modulated over a wide range (CMOS transistor ON/OFF conductance ratio at Radio Frequency (RF)/millimeter-wave frequencies is as high as 103-105), commutated LPTV networks break reciprocity within a deeply sub-wavelength form-factor with low loss and high linearity. The resulting nonreciprocal components find application in antenna interfaces of wireless communication systems, connecting the Transmitter (TX) and the Receiver (RX) to a shared antenna. This is particularly important for full-duplex wireless, where the TX and the RX operate simultaneously at the same frequency band and need to be highly isolated in order to maintain receiver sensitivity. Multiple fully-integrated full-duplex receivers are demonstrated in this dissertation that best show the synergy between the physical concept and application-based implementations by using circuit techniques to benefit the system-level performance, such as TX-side linearity enhancement and co-design and co-optimization of the antenna interface and the RX and utilization of the multi-phase structure of our antenna interfaces for analog beamforming in multi-antenna systems. Finally, this dissertation discusses some of the fundamental limits of space-time modulated nonreciprocal structures, as well as new directions to build nonreciprocal components which can ideally be infinitesimal in size. A novel family of inductor-less nonreciprocal components including circulators and isolators have been demonstrated that achieve a wide tuning range in an infinitesimal form-factor. This family of devices combine reciprocal and nonreciprocal modes of operation, through the transfer properties of fundamental and harmonics of the system and enable a wide variety of functionalities

Bibliography of Lewis Research Center technical publications announced in 1984

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1984. All the publications were announced in the 1984 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

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