Integrated Self-Interference Cancellation for Full-Duplex and Frequency-Division Duplexing Wireless Communication Systems

From wirelessly connected robots to car-to-car communications, and to smart cities, almost every aspect of our lives will benefit from future wireless communications. While promise an exciting future world, next-generation wireless communications impose requirements on the data rate, spectral efficiency, and latency (among others) that are higher than those for today's systems by several orders of magnitude. Full-duplex wireless, an emergent wireless communications paradigm, breaks the long-held assumption that it is impossible for a wireless device to transmit and receive simultaneously at the same frequency, and has the potential to immediately double network capacity at the physical (PHY) layer and offers many other benefits (such as reduced latency) at the higher layers. Recently, discrete-component-based demonstrations have established the feasibility of full-duplex wireless. However, the realization of integrated full duplex radios, compact radios that can fit into smartphones, is fraught with fundamental challenges. In addition, to unleash the full potential of full-duplex communication, a careful redesign of the PHY layer and the medium access control (MAC) layer using a cross-layer approach is required. The biggest challenge associated with full duplex wireless is the tremendous amount of transmitter self-interference right on top of the desired signal. In this dissertation, new self-interference-cancellation approaches at both system and circuit levels are presented, contributing towards the realization of full-duplex radios using integrated circuit technology. Specifically, these new approaches involve elimination of the noise and distortion of the cancellation circuitry, enhancing the integrated cancellation bandwidth, and performing joint radio frequency, analog, and digital cancellation to achieve cancellation with nearly one part-per-billion accuracy. In collaboration with researchers at higher layers of the stack, a cross-layer approach has been used in our full-duplex research and has allowed us to derive power allocation algorithms and to characterize rate-gain improvements for full-duplex wireless networks. To enable experimental characterization of full-duplex MAC layer algorithms, a cross-layered software-defined full-duplex radio testbed has been developed. In collaboration with researchers from the field of micro-electro-mechanical systems, we demonstrate a multi-band frequency-division duplexing system using a cavity-filter-based tunable duplexer and our integrated widely-tunable self-interference-cancelling receiver

대역 외 방해신호에 내성을 가지는 광대역 수신기에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 전기·컴퓨터공학부, 2018. 2. 남상욱.In this thesis, a study of wideband receivers as one of the practical SDR receiver implementations is presented. The out-of-band interference signal (or blocker), which is the biggest problem of the wideband receiver is investigated, and have studied how to effectively remove it. As a result of reviewing previous studies, we have developed a wideband receiver based on the current-mode receiver structure and attempted to eliminate the blocker. The contents of the step-by-step research are as follows. First, attention was paid to the linearity of a low-noise transconductance amplifier (LNTA), which is the base block of current-mode receivers. In current-mode receivers, the LNTA should have a high transconductance (Gm) value to achieve a low noise figure, but a high Gm value results in low linearity. To solve this trade-off, we proposed a linearization method of transconductors. The proposed technique eliminates the third-order intermodulation distortion (IMD3) in a feed-forward manner using two paths. A transconductor having a transconductance of 2Gm is disposed in the main path, and an amplifier having a gain of ∛2 and a Gm-sized transconductor are located in the auxiliary path. This structure allows for some fundamental signal loss but cancel the IMD3 component at the output. As a result, the entire transconductor circuit can have high linearity due to the removed IMD3 component. We have designed a reconfigurable high-pass filter using a linearized transconductor and have demonstrated its performance. The fabricated circuit achieved a high input-referred third-order intercept point(IIP3) performance of 19.4 dBm. Then, a further improved linearized transconductor is designed. Since the linearized transconductors have a high noise figure due to the additional circuitry used for linearization, we have proposed a more suitable form for application to LNTA through noise figure analysis. The improved LNTA is designed to operate in low noise mode when there is no blocker, and can be switched to operate in high linearity mode when the blocker exists. We also applied noise cancelling techniques to the receiver to improve the noise figure performance of the wideband receiver circuit. A feedback path has been added to the current-mode receiver structure consisting of the LNTA, the mixer and the baseband transimpedance amplifier (TIA), and the noise signal can be detected using this path. This feedback path also maintains the input matching of the receiver to 50 Ω in a wide bandwidth. By adding an auxiliary path to the receiver, the in-band signal is amplified and the detected noise is removed from the baseband. The completed circuit exhibited wideband performance from 0.025 GHz to 2 GHz and IIP3 performance of -6.9 dBm in the high linearity mode. Finally, we designed a double noise-cancelling wideband receiver circuit by improving the performance of a wideband receiver with high immunity to blocker signals. In previous receivers, the LNTA was operated in two modes depending on the situation. In the improved receiver, the Gm ratio of the linearized LNTA was changed and the RF noise-cancelling technique was applied. The input matching and noise cancelling scheme introduced in the previous circuit was also applied and a wideband receiver circuit was designed to perform double noise-cancelling. As a result, the linearization and noise-cancellation of LNTA could be achieved at the same time, and the completed receiver circuit showed high IIP3 performance of 5 dBm with minimum noise figure of 1.4 dB. In conclusion, this thesis proposed a linearization technique for transconductor circuit and designed a wideband receiver based on current-mode receiver. The designed receiver circuit experimentally verified that it has low noise figure performance and high IIP3 performance and is tolerant to out-of-band blocker signals.Chapter 1. Introduction 1 1.1. Motivation of Wideband Receiver Architecture 2 1.2. Challenges in Designing Wideband Receiver 7 1.3. Prior Researches 13 1.3.1. N-Path Filter 14 1.3.2. Feed-Forward Blocker Filtering 16 1.3.3. Current-Mode Receiver 18 1.4. Research Objectives and Thesis Organization 22 Chapter 2. Transconductor Linearization Technique and Design of Tunable High-pass Filter 24 2.1. Transconductor Linearization Technique 27 2.2. Design of Tunable High-pass Filter 36 2.3. Measurement Results 41 2.4. Conclusions 46 Chapter 3. Wideband Noise-Cancelling Receiver Front-End Using Linearized Transconductor 47 3.1. Low-Noise Transconductance Amplifier Based on Linearized Transconductor 49 3.2. Wideband Noise-Cancelling Receiver Architecture 58 3.3. Measurement Results 64 3.4. Conclusions 70 Chapter 4. Blocker-Tolerant Wideband Double Noise-Cancelling Receiver Front-End 71 4.1. Linearized Noise-Cancelling Low-Noise Transconductance Amplifier 73 4.2. Wideband Double Noise-Cancelling Receiver Front-End 83 4.3. Measurement Results 90 4.4. Conclusions 97 Chapter 5. Conclusions 98 Bibliography 102 Abstract in Korean 112Docto

Modern digital flight control system design for VTOL aircraft

Methods for and results from the design and evaluation of a digital flight control system (DFCS) for a CH-47B helicopter are presented. The DFCS employed proportional-integral control logic to provide rapid, precise response to automatic or manual guidance commands while following conventional or spiral-descent approach paths. It contained altitude- and velocity-command modes, and it adapted to varying flight conditions through gain scheduling. Extensive use was made of linear systems analysis techniques. The DFCS was designed, using linear-optimal estimation and control theory, and the effects of gain scheduling are assessed by examination of closed-loop eigenvalues and time responses

RF Amplification and Filtering Techniques for Cellular Receivers

The usage of various wireless standards, such as Bluetooth, Wi-Fi, GPS, and 4G/5G cellular, has been continually increasing. In order to utilize the frequency bands efficiently and to support new communication standards with lower power consumption, lower occupied volume and at reduced costs, multimode transceivers, software defined radios (SDRs), cognitive radios, etc., have been actively investigated. Broadband behavior of a wireless receiver is typically defined by its front-end low-noise amplifier (LNA), whose design must consider trade-offs between input matching, noise figure (NF), gain, bandwidth, linearity, and voltage headroom in a given process technology. Moreover, monolithic RF wireless receivers have been trending toward high intermediatefrequency (IF) or superhetrodyne radios thanks to recent breakthroughs in silicon integration of band-pass channel-select filters. The main motivation is to avoid the common issues in the currently predominant zero/low-IF receivers, such as poor 2nd-order nonlinearity, sensitivity to 1/f (i.e. flicker) noise and time-variant dc offsets, especially in the fine CMOS technology. To avoid interferers and blockers at the susceptible image frequencies that the high-IF entails, band-pass filters (BPF) with high quality (Q) factor components for sharp transfer-function transition characteristics are now required. In addition, integrated low-pass filters (LPF) with strong rejection of out-of-band frequency components are essential building blocks in a variety of applications, such as telecommunications, video signal processing, anti-aliasing filtering, etc. Attention is drawn toward structures featuring low noise, small area, high in-/out-of-band linearity performance, and low-power consumption. This thesis comprises three main parts. In the first part (Chapters 2 and 3), we focus on the design and implementation of several innovative wideband low-noise (transconductance) amplifiers [LN(T)A] for wireless cellular applications. In the first design, we introduce new approaches to reduce the noise figure of the noise-cancellation LNAs without sacrificing the power consumption budget, which leads to NF of 2 dB without adding extra power consumption. The proposed LNAs also have the capability to be used in current-mode receivers, especially in discrete-time receivers, as in the form of low noise transconductance amplifier (LNTA). In the second design, two different two-fold noise cancellation approaches are proposed, which not only improve the noise performance of the design, but also achieve high linearity (IIP3=+4.25 dBm). The proposed LN(T)As are implemented in TSMC 28-nm LP CMOS technology to prove that they are suitable for applications such as sub-6 GHz 5G receivers. The second objective of this dissertation research is to invent a novel method of band-pass filtering, which leads to achieving very sharp and selective band-pass filtering with high linearity and low input referred (IRN) noise (Chapter 4). This technique improves the noise and linearity performance without adding extra clock phases. Hence, the duty cycle of the clock phases stays constant, despite the sophisticated improvements. Moreover, due to its sharp filtering, it can filter out high blockers of near channels and can increase the receiver’s blocker tolerance. With the same total capacitor size and clock duty cycle as in a 1st-order complex charge-sharing band-pass filter (CS BPF), the proposed design achieves 20 dB better out-of-band filtering compared to the prior-art 1st-order CS BPF and 10 dB better out-of-band filtering compared to the conventional 2nd-order C-CS BPF. Finally, the stop-band rejection of the discrete-time infinite-impulse response (IIR) lowpass filter is improved by applying a novel technique to enhance the anti-aliasing filtering (Chapter 5). The aim is to introduce a 4th-order charge rotating (CR) discrete-time (DT) LPF, which achieves the record of stop-band rejection of 120 dB by using a novel pseudolinear interpolation technique while keeping the sampling frequency and the capacitor values constant

Controlling a contactless planar actuator with manipulator

An existing magnetically levitated planar actuator with manipulator has been studied and improved from a control point of view. This prototype consists of a magnetically levitated six-degree-of-freedom (6-DOF) planar actuator with moving magnets, with a 2-DOF manipulator on top of it. This system contains three different contactless technologies: contactless bearing and propulsion of the planar actuator, wireless powering of the manipulator, and wireless communication and control of the manipulator. The planar actuator (PA) consists of a Halbach magnet array, which is levitated and controlled in all six DOF’s above a stationary coil array. The PA is propelled in two horizontal translational DOF’s while the other four DOF’s are stabilized to accomplish a stiff bearing. Each active coil contributes to the production of forces and torques acting on the magnet array. Since the number of active coils is much larger than the number of DOF’s, the desired force production can be distributed over many coils. Therefore, a commutation algorithm has to be used to invert the mapping of the forces and torques exerted by the set of active coils as a function of the coil currents and the position and orientation of the translator. One method for linearization and decoupling of the forces and torques was developed in the past. The method is called direct wrench decoupling and guaranties minimal dissipation of energy. However, no constraints on the maximum current can be given. This study proposes two novel, norm-based commutation methods: l8-norm and clipped l2-norm based commutation. Both methods can put bounds on the maximum currents in the coils to prevent saturation of the current amplifiers. The first method focuses on minimization of the maximum current whereas the second method limits the peak current while it minimizes the power losses. Consequently, a higher acceleration of the translator can be achieved and/or less powerful (cheaper) current amplifiers can be utilized and/or fewer commutation errors arise. Only a long-stroke translational movement of the moving magnet planar actuators has been considered in the past. The possibility of a completely propelled and controlled rotation about the vertical axis instead of just stabilizing it for bearing has been analyzed in this thesis from a control point of view. Enhancing the planar actuator with a long-range rotation will increase its utility value and opens new application areas. Based on this investigation, a novel coil array with a triangular grid of rounded coils has been proposed for better controllability in any orientation of the PA. In addition, other coil and magnet topologies have been studied from a control point of view for their suitability for full rotation. The influence of different kinds of error-causes on the commutation precision has been studied. From this investigation, it has been found that the offsets of the measurement system have the highest influence on the precision of the commutation. Investigation of the convergence of the procedure for estimation and elimination of these offsets has been performed. Although it was not proven that the procedure could be applied on the whole workspace of the PA, the convergence has been shown at least for all the investigated points. From this investigation, convergence for any position in the workspace of the PA is expected. It was found that it is possible to use the procedure also with different topologies and with different commutations. A novel wireless link has been developed for the real-time control of a fast motion system. The wireless link communicates via infrared-light transceivers and the link has a delay and a packet-loss ratio almost indistinguishable from the wired connection for the bandwidth of the system up to several kilohertz. The clipped l2-norm based commutation method has been successfully tested on the experimental setup after improving the measurement system, the contactless energy transfer and the wireless communication. With a new, interferometer sensor system, a well-controlled PA with two long-stroke DOF’s has become available. Improved contactless energy transfer does not cause increased electromagnetic interference during switching between the primary coils any more and the wireless connection using the infrared link provides a reliable communication channel between the manipulator and the fixed world. Several control approaches have been tested on the experimental setup. Both, the classical PID control, Sliding-mode control and Iterative learning control have been implemented. Each controller brought better performance than the previous one. Also, a fourth-order trajectory and enhanced feedforward control helped to improve performance. Finally, the tracking errors, in comparison to the initial situation, were reduced by a factor 10 (and even more than by a factor 50 with deactivated contactless energy transfer) while the velocity and acceleration of the system were a factor 4 and 14, respectively, higher

Automatic Flight Control Systems

The history of flight control is inseparably linked to the history of aviation itself. Since the early days, the concept of automatic flight control systems has evolved from mechanical control systems to highly advanced automatic fly-by-wire flight control systems which can be found nowadays in military jets and civil airliners. Even today, many research efforts are made for the further development of these flight control systems in various aspects. Recent new developments in this field focus on a wealth of different aspects. This book focuses on a selection of key research areas, such as inertial navigation, control of unmanned aircraft and helicopters, trajectory control of an unmanned space re-entry vehicle, aeroservoelastic control, adaptive flight control, and fault tolerant flight control. This book consists of two major sections. The first section focuses on a literature review and some recent theoretical developments in flight control systems. The second section discusses some concepts of adaptive and fault-tolerant flight control systems. Each technique discussed in this book is illustrated by a relevant example

Fourth Aircraft Interior Noise Workshop

The fourth in a series of NASA/SAE Interior Noise Workshops was held on May 19 and 20, 1992. The theme of the workshop was new technology and applications for aircraft noise with emphasis on source noise prediction; cabin noise prediction; cabin noise control, including active and passive methods; and cabin interior noise procedures. This report is a compilation of the presentations made at the meeting which addressed the above issues

New Approaches in Automation and Robotics

The book New Approaches in Automation and Robotics offers in 22 chapters a collection of recent developments in automation, robotics as well as control theory. It is dedicated to researchers in science and industry, students, and practicing engineers, who wish to update and enhance their knowledge on modern methods and innovative applications. The authors and editor of this book wish to motivate people, especially under-graduate students, to get involved with the interesting field of robotics and mechatronics. We hope that the ideas and concepts presented in this book are useful for your own work and could contribute to problem solving in similar applications as well. It is clear, however, that the wide area of automation and robotics can only be highlighted at several spots but not completely covered by a single book

Proceedings of the Seventeenth Annual Conference on Manual Control

Manual control is considered, with concentration on perceptive/cognitive man-machine interaction and interface