Real-Time Dispersion Code Multiple Access (DCMA) for High-Speed Wireless Communications

We model, demonstrate and characterize Dispersion Code Multiple Access (DCMA) and hence show the applicability of this purely analog and real-time multiple access scheme to high-speed wireless communications. We first mathematically describe DCMA and show the appropriateness of Chebyshev dispersion coding in this technology. We next provide an experimental proof-of-concept in a 2 X 2 DCMA system. Finally,we statistically characterize DCMA in terms of bandwidth, dispersive group delay swing, system dimension and signal-to-noise ratio

Time-Reversal Routing for Dispersion Code Multiple Access (DCMA) Communications

We present the modeling and characterization of a time-reversal routing dispersion code multiple access (TR-DCMA) system. We show that this system maintains the low complexity advantage of DCMA transceivers while offering dynamic adaptivity for practial communication scenarios. We first derive the mathematical model and explain operation principles of the system, and then characterize its interference, signal to interference ratio, and bit error probability characteristics

Real-Time Electromagnetic Signal Processing: Principles and Illustrations

Real-time electromagnetic signal processing has recently appeared as a novel signal-processing paradigm to manipulate and control electromagnetic signals in real time directly in the analog domain. This has led to attractive alternatives to conventional digital techniques, which typically suffer from poor performances and high cost at microwave and millimeter wave frequencies. This novel paradigm is based on dispersion-engineered electromagnetic structures, and in this review chapter, two types of structures are presented and discussed in details: phasers and metasurfaces. While phasers are typically group delay engineered to manipulate and rearrange spectral components in the time domain, metasurfaces enhances these functionalities by providing spatial processing in addition to temporal processing. Two kinds of phasers are presented here: static and dynamic all-pass C-section phasers, and all-dielectric metasurface-based spatial phasers. Finally, two applications illustrating real-time signal processing are discussed: 2D beam scanning leaky-wave antenna for high-resolution spectrum analysis and a dispersion code multiple access (DCMA) system

Dispersion Based Real-Time Analog Signal Processing (R-ASP) and Application to Wireless Communications

RÉSUMÉ Nous sommes confrontés à une demande explosive de systèmes radio plus rapides, plus fiables et plus écoénergétiques, pour la communication sans fil 5G par exemple. On s’attend à ce que la capacité des données mobiles dépasse 1000 fois ce qu’elle est actuellement dans la prochaine décennie. Un tel volume de données nécessite un grand spectre de bande passante. Aux fréquences radio-fréquences (RF) faibles, le spectre est congestionné par des milliards d’appareils radio. Dans les hautes fréquences, le spectre de bande passante ultra large (UWB) est moins congestionné. Cependant, le traitement d’un tel signal UWB RF pose de grands défis au niveau du traitement du signal (DSP) numérique, qui est habituellement utilisé pour les basses fréquences et les bandes passantes étroites. Les problèmes dont souffre le DSP pour les signaux hautes fréquences sont la limitation de la vitesse, le coût élevé et la forte consommation d’énergie pour la conversion analogique / numérique (ADC). Par conséquent, une technique de traitement en temps réel et purement analogique est souhaitable. En optique, les gens ont traité des signaux RF UWB avec des approches photoniques hyperfréquences en temps réel, mais cela impliquait une conversion électrique / optique coûteuse. Le traitement de signal analogique d’une onde radio en temps réel (R-ASP) est une alternative attrayante et moins exploitée. Le premier chapitre présente l’état de l’art de la technologie R-ASP ainsi que la contribution de la thèse. Le composant au coeur du traitement R-ASP s’appelle "phaseur", un composant qui fournit un retard de groupe spécifié � (!) à une onde radio. Un phaseur, en réponse à un signal d’excitation large bande, réorganise les composants spectraux dans le temps. La façon dont un phaseur réorganise le spectre dépend de la fonction de retard de groupe, � (!). Différentes applications R-ASP peuvent nécessiter des profils de retard de groupe différents. Le chapitre 2 introduit le concept de retard de groupe, présente différentes technologies phaseur, et présente une méthode pour augmenter la quantité de délai de groupe en utilisant des phaseurs réfléchissants passifs. Un phaseur passif et passe-tout (qui ne filtre aucune fréquence) affiche une perte qui est proportionnelle au retard de groupe, ce qui entraîne une distorsion du signal. Le chapitre trois présente une solution à ce problème, qui consiste en une mise en cascade d’un phaseur ayant du gain et un phaseur ayant des pertes.---------- ABSTRACT We are facing exploding demands for faster, more reliable, more energy-efficient radio systems, such as for instance 5G wireless communication. It is expected that for the next decade the mobile data capacity would exceed 1000 times higher than it is right now. Such high data volume requires large bandwidth spectrum resources. In low RF frequencies, the precious spectrum have been congested by zillions of radio devices. In high frequencies, such as millimeter wave, ultra wideband (UWB) spectrum is much easier available. However, processing UWB RF signal poses great difficulties on conventional digital signal processing (DSP) technique that has prevailed for low frequency and small bandwidth processing. For instance, DSP suffers limited speed, high cost and high power consumption for analog/digital conversion (ADC). Therefore, real-time and purely analog processing technique is desirable. In optics, people have been processing UWB RF signal with microwave photonics approaches, which is real-time, but involves expensive and lossy electrical/optical conversion. The direct radio Real-time Analog Signal Processing (R-ASP) is thus tractive but less exploited. Chapter 1 presents the advancements of R-ASP along with the contributions of the thesis. The core of R-ASP is “phaser”, which is a group delay engineered component that provides specified group delay function � (!). A phaser, in response to a wideband signal excitation, rearranges spectral components in time. The way a phaser arranges spectral components is controlled by the group delay function, � (!). Different R-ASP applications may require different group delay profiles. Chapter 2 introduces the concept of group delay engineering, different phaser technologies, and presents an R-ASP resolution (group delay swing) enhancement example using passive reflective phaser units. Passive phaser exhibits loss that is proportional to the group delay, i.e. imbalance amplitude, which typically results in undesired processing distortion. It is found that a phaser unit loaded with gain (G) and another loaded with equalized loss (L = 1/G) provide symmetric amplitudes (about 0 dB) and identical group delays. Cascading such gain and loss pair yields real all-pass amplitude. Moreover, the group delay can be tuned by the gain and loss. Chapter 3 introduces the gain-loss equalization concept, mathematically presents the device modeling, and experimentally demonstrated the prototype

Time-reversal routing for dispersion code multiple access (DCMA) communications

ABSTRACT: We present the modeling and characterization of a time-reversal routing dispersion code multiple access (TR-DCMA) system. We show that this system maintains the low complexity advantage of DCMA transceivers while offering dynamic adaptivity for practical communication scenarios. We first derive the mathematical model and explain operation principles of the system, and then characterize its interference, signal to interference ratio and bit error probability characteristics

Microwave Hilbert Transformer and its Applications in Real-time Analog Processing (RAP)

A microwave Hilbert transformer is introduced as a new component for Real-time Analog Processing (RAP). In contrast to its optical counterpart, that resort to optical fiber gratings, this Hilbert transformer is based on the combination of a branch-line coupler and a loop resonator. The transfer function of the transformer is derived using signal flow graphs, and two figures of merits are introduced to effectively characterize the device: the rotated phase and the transition bandwidth. Moreover, a detailed physical explanation of its physical operation is given, using both a steady-state regime perspective and a transient regime perspective. The microwave RAP Hilbert transformer is demonstrated experimentally, and demonstrated in three applications: edge detection, peak suppression and single sideband modulation

Towards Radio Analog Signal Processing

RÉSUMÉ La demande insatiable pour les services de radio et communication à large bande, stimule les fabricants à chercher des nouvelles façons d’augmenter la largeur de bande spectrale des systèmes. Traitement numérique du signal (DSP) comme la technologie la plus commune des radios d’aujourd’hui est souple, reproductible, compact, et fiable en basse fréquence. Cependant,le système digital est plage dynamique limitée, le largeur de bande du système DSP est limité par la fréquence d’échantillonnage. A haute fréquence, telles que la fréquence d’onde millimétrique, le système DSP a un manque de performance et une consommation de puissance excessive. En outre, la complexité et le coût de système augmente aux fréquences plus élevées. Contrairement à DSP, les systèmes traitement radio-analogique du signal (R-ASP) sont bonnes performances à haute fréquence. Les systèmes R-ASP manipulent des signaux à large bande, temporellement sous leur forme analogique d’origine. Donc, ils n’ont pas besoin des convertisseurs A/D et D/A, et des convertisseurs haut/bas, résultant complexité inférieure à vitesse plus élevée, ce qui peut offrir des solutions sans précédent dans le domaine de l’ingénierie de radio. Phaser comme une structure de délai dispersive (DDS) contrôlable est le noyau d’un système R-ASP. Les composantes des fréquences du signal dans le temps se différencient après avoir traversé un phaser. Cette caractéristique du phaser le rend pratique pour l’application radio analogique haute vitesse, comme renifleur de spectre, multiplexage par division de fréquence (FDM), et impulsion radio. Cette thèse par articles présente les concepts et les améliorations R-ASP, sur la base du phaser, comme une alternative potentielle au traitement basé sur DSP, pour l’application de radio haute fréquence et haute vitesse. Le premier Chapitre traite de la motivation R-ASP, contributions de la thèse et de l’organisation. Les concepts et les caractéristiques du phaser,les nouvelles techniques pour améliorer la dispersion des phasers ainsi que la performance du système R-ASP, en fonction des applications sont proposées dans le Chapitre 2. Les Chapitres 3 à 6 sont les articles qui introduisent des nouvelles applications du R-ASP. Dans le Chapitre 3, une nouvelle technique de loop afin d’améliorer la résolution du phaser est proposé. En plus des fréquence mètres et les discriminateurs de fréquence, cette technique peut facilement appliquer à divers autres systèmes en temps réel, tels que les transformateurs de Fourier en temps réel, convolveurs, corrélateurs, et les radars compressifs.----------ABSTRACT Insatiable demand for broadband radio and communication services spurs the manufacturers to seek new ways to increase the spectral bandwidth of the systems. Digital Signal Processing (DSP) as the most common technology of Today’s radios is flexible, reproducible, compact, and reliable at low spectral bandwidth. However, digital system is limited precision and dynamic range, the bandwidth of the DSP system is limited by sampling rate. At high frequency, such as millimeter-wave frequency, the DSP system is poor performance and power hungry. Moreover, the complexity and cost of the system increase at higher frequency. In contrast of DSP, Radio-Analog Signal Processing (R-ASP) systems have a good performance at high frequency. R-ASP systems manipulate broadband signals, temporally in their original analog form. So, They don’t need A/D and D/A, and up/down converters, resulting lower complexity at higher speed, which may offer unprecedented solutions in the major areas of radio engineering. Phaser as an engineerable dispersive delay structure (DDS) is the core of an R-ASP system. The component frequencies of the signal differentiate in time after passing through a phaser. This characteristic of the phaser makes it convenient for high speed analog radio application, such as frequency sniffer, frequency division multiplexing (FDM), and impulse radio. This paper based dissertation introduces R-ASP concepts and enhancements, based on the phaser, as a potential alternative to DSP-based processing, for high speed and high frequency radio applications. The first Chapter discusses R-ASP motivation, thesis contributions and organization. The concepts of the phaser and phaser characteristics, new techniques to enhance the dispersion of the phasers as well as performance of the R-ASP system, depending on the applications are proposed in Chapter 2. Chapters 3 to 6 are the articles that introduce new applications of ASP. In Chapter 3, a novel loop technique to enhance the resolution of the phaser is proposed. In addition to frequency meters and frequency discriminators, this technique may readily by applied to various other real-time systems, such as real-time Fourier transformers, convolvers, correlators, and compressive radars. The radio-analog signal processing system has a lot of applications in the impulse regime. However, UWB pulse generation is complex and high cost. This issue is addressed in Chapter 4, proposing a low-cost analog pulse compression technique for UWB pulse generation. In Chapter 5, a stepped group delay phaser is introduced for real-time spectrum sniffing application. The system listens to its radio environment through an antenna, and determines, in real time, the presence or absence of active channels in this environment

Synthesis and monolithic integration of analogue signal processing networks

Data traffic of future 5G telecommunication systems is projected to increase 10 000-fold compared to current rates. 5G fronthaul links are therefore expected to operate in the mm-wave spectrum with some preliminary International Telecommunication Union specifications set for the 71-76 and 81-86 GHz bands. Processing 5 GHz as a single contiguous band in real-time, using existing digital signal processing (DSP) systems, is exceedingly challenging. A similar challenge exists in radio astronomy, with the Square Kilometer Array project expecting data throughput rates of 15 Tbits/s at its completion. Speed improvements on existing state-of-the-art DSPs of 2-3 orders of magnitude are therefore required to meet future demands. One possible mitigating approach to processing wideband data in real-time is to replace some DSP blocks with analog signal processing (ASP) equivalents, since analogue devices outperform their digital counterparts in terms of cost, power consumption and the maximum attainable bandwidth. The fundamental building block of any ASP is an all-pass network of prescribed response, which can always be synthesized by cascaded first- and second-order all-pass sections (with two cascaded first-order sections being a special case of the latter). The monolithic integration of all-pass networks in commercial CMOS and BiCMOS technology nodes is a key consideration for commercial adaptation of ASPs, since it supports mass production at reduced costs and operating power requirements, making the ASP approach feasible. However, this integration has presented a number of yet unsolved challenges. Firstly, the state-of-the-art methods for synthesizing quasi-arbitrary group delay functions using all-pass elements lack a theoretical synthesis procedure that guarantees minimum-order networks. In this work an analytically-based solution to the synthesis problem is presented that produces an all-pass network with a response approximating the required group delay to within an arbitrary minimax error. This method is shown to work for any physical realization of second-order all-pass elements, is guaranteed to converge to a global optimum solution without any choice of seed values as an input, and allows synthesis of pre-defined networks described either analytically or numerically. Secondly, second-order all-pass networks are currently primarily implemented in off-chip planar media, which is unsuited for high volume production. Component sensitivity, process tolerances and on-chip parasitics often make proposed on-chip designs impractical. Consequently, to date, no measured results of a dispersive on-chip second-order all-pass network suitable for ASP applications (delay Q-value (QD) larger than 1) have been presented in either CMOS or BiCMOS technology nodes. In this work, the first ever on-chip CMOS second-order all-pass network is proposed with a measured QD-value larger than 1. Measurements indicate a post-tuning bandwidth of 280 MHz, peak-to-nominal delay variation of 10 ns, QD-value of 1.15 and magnitude variation of 3.1 dB. An active on-chip mm-wave second-order all-pass network is further demonstrated in a 130 nm SiGe BiCMOS technology node with a bandwidth of 40 GHz, peak-to-nominal delay of 62 ps, QD-value of 3.6 and a magnitude ripple of 1.4 dB. This is the first time that measurement results of a mm-wave bandwidth second-order all-pass network have been reported. This work therefore presents the first step to monolithically integrating ASP solutions to conventional DSP problems, thereby enabling ultra-wideband signal processing on-chip in commercial technology nodes.Thesis (PhD)--University of Pretoria, 2018.Square Kilometer Array (SKA) project - postgraduate scholarshipElectrical, Electronic and Computer EngineeringPhDUnrestricte

Bit-Error-Rate-Minimizing Channel Shortening Using Post-FEQ Diversity Combining and a Genetic Algorithm

In advanced wireline or wireless communication systems, i.e., DSL, IEEE 802.11a/g, HIPERLAN/2, etc., a cyclic prefix which is proportional to the channel impulse response is needed to append a multicarrier modulation (MCM) frame for operating the MCM accurately. This prefix is used to combat inter symbol interference (ISI). In some cases, the channel impulse response can be longer than the cyclic prefix (CP). One of the most useful techniques to mitigate this problem is reuse of a Channel Shortening Equalizer (CSE) as a linear preprocessor before the MCM receiver in order to shorten the effective channel length. Channel shortening filter design is a widely examined topic in the literature. Most channel shortening equalizer proposals depend on perfect channel state information (CSI). However, this information may not be available in all situations. In cases where channel state information is not needed, blind adaptive equalization techniques are appropriate. In wireline communication systems (such as DMT), the CSE design is based on maximizing the bit rate, but in wireless systems (OFDM), there is a fixed bit loading algorithm, and the performance metric is Bit Error Rate (BER) minimization. In this work, a CSE is developed for multicarrier and single-carrier cyclic prefixed (SCCP) systems which attempts to minimize the BER. To minimize the BER, a Genetic Algorithm (GA), which is an optimization method based on the principles of natural selection and genetics, is used. If the CSI is shorter than the CP, the equalization can be done by a frequency domain equalizer (FEQ), which is a bank of complex scalars. However, in the literature the adaptive FEQ design has not been well examined. The second phase of this thesis focuses on different types of algorithms for adapting the FEQ and modifying the FEQ architecture to obtain a lower BER. Simulation results show that this modified architecture yields a 20 dB improvement in BER