One of the key building blocks in a direct-conversion receiver is the low noise amplifier (LNA), which needs to provide a sufficient gain with a low noise figure for the RF front-end. However, the wideband nature of the receiver imposes harsh requirements on the LNA. It is difficult to achieve desired performance goals over the wide frequency range without excessive power consumption. To deal with this problem, this thesis proposes a novel band-selective UWB LNA. Utilizing the frequency hopping property of the MB-OFDM system, the proposed method switches the operating frequency of the LNA in real time following the MB-OFDM's hopping pattern so that optimal gain and noise performance can be achieved in each frequency band. Unlike the conventional approach, this LNA does not need to cover the entire band simultaneously, thus excessive power consumption is avoided. Fabricated in a 0.18-mum CMOS process, the proposed LNA achieves a peak power gain of 16 dB and a minimum noise figure of 2.74 dB at a low power consumption of less than 12 mW. / Other challenges in direct-conversion MB-OFDM receivers include ultra-short band switching time and wide LO frequency range. The single-sideband (SSB) generation is an attractive method for a fast-hopping multi-band LO generator. However, it involves LO frequency synthesis in an open-loop architecture, and thus the spurious-tone performance becomes critical in maintaining the LO signal integrity. Since the accuracy of the SSB generation and the spurious-tone power are difficult to control in a high-frequency operation, a 4.5-GHz SSB upconverter system was fabricated in a standard 0.18-mum CMOS process to investigate its performance against process variation. Some precise quadrature signal generation circuits such as divider and polyphase filter are employed. Experimental results show that the fabricated SSB upconverter system achieves image rejection of higher than 48 dB and spurious-tone suppression of higher than 32 dB. / The use of an active downconversion mixer is an alternative to relax the LNA requirements for direct-conversion MB-OFDM UWB receivers. However, its linearity becomes a problem when the bandwidth is ultra wide. In this thesis, the static current bleeding technique is used in the UWB downconversion mixer to improve its linearity. By injecting a DC current to the RF transconductor for linearization, the mixer's transconductance is enhanced while the noise from the LO switches is not affected. As a result, the conversion gain increases and the noise figure improves. Fabricated in a 0.18-mum CMOS process, the UWB downconversion mixer achieves a peak conversion gain of 4.1 dB, a peak IIP3 of --2.5 dBm, and a minimum double-sideband (DSB) noise figure of 11.7 dB at a low power consumption of 6 mW. / Ultra-wideband (UWB) is a short-range, high-data-rate communication system for Wireless Personal Area Networks (WPAN) based on the IEEE 802.15.3a physical layer standard. The allocated frequency range is from 3.1 to 10.6 GHz, in which 14 bands are defined. The first band group, which is assigned to the mandatory Mode 1 devices, consists of three bands. In UWB systems, multi-band orthogonal frequency division multiplexing (MB-OFDM) is the dominant modulation scheme for its high spectral flexibility and its similarity in communication architecture with other existing wireless communication standards, such as IEEE 802.11a/b/g and WiMAX. For practical reasons, the direct-conversion architecture is widely considered the best architecture to implement an MB-OFDM UWB receiver, which has advantages of low power consumption and high integration level. Nevertheless, there are some performance limitations in direct-conversion MB-OFDM UWB receivers. In this thesis, some key building blocks in the RF front-end of the direct-conversion MB-OFDM UWB receivers for use in Mode 1 devices are investigated to overcome such limitations. / Tang, Siu Kei. / "May 2008." / Adviser: Pun Kong Pang. / Source: Dissertation Abstracts International, Volume: 70-03, Section: B, page: 1857. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (p. 161-169). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Besides colorless ONUs, we investigate potentially low cost, high speed vertical-cavity-surface-emitting lasers (VCSELs) for use in future access networks. VCSELs are attractive because they may meet the stringent size, power dissipation and cost constraints of access network components. We carry out experiments to demonstrate that up to 20 Gb/s direct modulation of long wavelength VCSEL is possible and evaluate their performance as high-speed transceivers. / In order to reduce the complexity and costs of ONU transceiver, we propose a scheme based on a nonreciprocal optical modulator and a linear loop mirror for receiving downstream and sending upstream data We show that the nonreciprocity of traveling wave electrodes can selectively impress signal modulation onto the reflected upstream signals only. Monolithic integrated transceivers may thus remodulate downstream signals for upstream data transmission without needing integrated optical circulators. The proposed ONU is thus compatible with monolithic integration. / In this thesis, we describe our research on photonic devices and subsystems for future access networks. Since optical network units (ONUs) are the most cost-sensitive parts, we first investigate the use of advanced modulation format in colorless ONU structure. We implement a scheme which uses dark return-to-zero (DRZ) for downstream transmission and remodulation of it using a differential-phase-shift-keying (DPSK) for upstream both at 10 Gb/s. We also experimentally demonstrate silicon microring based optical frequency discriminators for use in demodulating DPSK and differential-quadrature-phase-shift-keying (DQPSK) signals. We show that the scheme is robust to variations in bit-rates in contrast with conventional Mach-Zehnder delay interferometer scheme. / Internet traffic has undergone tremendous growth in the past decades and has already penetrated into the daily lives of the general population. Demand for new high bandwidth services is beginning to drive the deployment of optical fiber-based access networks to solve the so-called last mile bottleneck around the world. Passive optical networks (PON) are attractive because there are no active components in the transmission line, thus reducing operational and deployment costs. Time-division-multiplexing (TDM) used in currently deployed PON, in which the bandwidth is shared among the users by time domain multiplexing, does not fully utilize the bandwidth potential of optical fibers and will not be able to satisfy the bandwidth demand in access networks in the near future. Among the advanced multiplexing techniques, wavelength-division-multiplexing (WDM) PON is a good candidate technology for providing sustained bit-rates beyond 10 Gb/s in access networks. However, reduction of costs in WDM PON remains a key challenge for their practical deployment. / Wired and wireless hybrid optical access networks are also investigated. Radio-over-fiber is one low-cost approach to deliver broadband wireless services, in which radio signals at the carrier frequency are delivered over optical networks from a central office to remote antenna base stations. Generation of high frequency carrier and radio frequency fading are the main research challenges. We propose and demonstrate frequency upconversion based on frequency doubling and quadrupling. Novel wired and wireless hybrid subsystems that mitigate millimeter-wave signal distortion are also demonstrated. / Xu, Lin. / Adviser: H. K. Tsang. / Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Wong Chi Sang. / "August 2002." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

"Faster, higher, stronger"---the Olympic motto is being pursued and practised in the design of broadband wireless communication systems. Motivated by the huge demands for fast and reliable communications over wireless channels, broadband communication systems are required to provide faster (low-complexity) data processing, higher data throughput and stronger (lower error rate) performance. In practice, however, broadband communication systems must cope with critical performance-limiting challenges that include time- and frequency-selective fading channels, noise, inter-symbol interference (ISI), intercarrier interference (ICI) as well as power and bandwidth constraints. To address these challenges, this thesis investigates several physical layer aspects of broadband wireless communication systems. / Incorporating OFDM into multiple-input multiple-output (MIMO) system, MIMO-OFDM has been shown to provide larger channel capacity and greater diversity gain. However, current coding schemes for MIMO-OFDM are either space-time coded (STC) OFDM without the guarantee of full diversity gains or space-frequency coding (SFC) with a greater loss of data rate. Furthermore, most existing STC and SFC have focused on quasi-static fading which is not practical for broadband wireless communications. When multi-band OFDM (MB-OFDM) is applied to ultra-wide band (UWB) communications, a high diversity can be obtained, but in the expense of a much lower (close to half) data rate. To address the limitations of existing coding schemes for broadband wireless communication systems, this thesis: (i) proposes a space-time-frequency coding (STFC) that can achieve maximum diversity and maximum symbol rate transmission over MIMO block-fading channels; (ii) derives a high-rate full-diversity SFC from STFC tailored for frequency-selective fading channels; and (iii) proposes a high-rate high-diversity algebraic time-frequency coding (ATFC) for MB-OFDM system. / Orthogonal frequency division multiplexing (OFDM) is an effective technique to eliminate ISI in broadband wireless communications. This thesis studies the problem of training-based OFDM channel estimation and proposes a training method that minimizes the number of pilots employed to achieve a desired bit error rate (BER) performance. A clustered pilot pattern is further proposed to enhance the BER performance. Focusing on OFDM frequency synchronization, this thesis also proposes a clustered pilot tones placement and a novel pilot sequence design for carrier frequency offset (CFO) compensation. The analytical and simulation results show that the root mean square error (RMSE) of the CFO estimate can be greatly reduced. / Zhang Wei. / "July 2005." / Adviser: Pak-Chung Ching. / Source: Dissertation Abstracts International, Volume: 67-01, Section: B, page: 0461. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 126-143). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Ce travail de thèse porte sur la conception d’un « laboratoire-sur-fibre » original dédié à l’analyse moléculaire à distance, sans marquage et in vivo compatible dans l’avenir avec les examens endoscopiques et dédié à l’assistance aux diagnostiques. Notre approche est basée sur l’utilisation de faisceaux de fibres microstructurés. Lorsqu’ils sont correctement conçus et recouverts d’une couche d’or, ces assemblages de fibres présentent des propriétés plasmoniques intéressantes. Dans un premier temps, le modèle numérique utilisé pour atteindre une meilleure compréhension des phénomènes physiques impliqués dans l’optimisation de la sensibilité des capteurs est expliqué. Les simulations, basées sur l’optique géométrique, ont été utilisées pour optimiser la géométrie des pointes et l’épaisseur de la couche d’or dans le but d’améliorer les performances analytiques et permettre ainsi des détections d’interactions biochimiques. Le processus de fabrication des capteurs est ensuite expliqué depuis leur structuration par gravure chimique effectuée à l’ISM (Bordeaux) jusqu’à leur métallisation réalisée au CEA Grenoble. Une comparaison entre les comportements théoriques et expérimentaux et alors menée pour comprendre l’influence de l’hétérogénéité du dépôt d’or et des surfaces gravées sur la sensibilité optique. Ces propriétés optiques sont ensuite exploitées jusqu’à la preuve de concept d’analyses biochimiques déportées. Cette étape a été réalisée en deux temps : d’abord la sensibilité à l’indice local a été démontrée en détectant l’adsorption d’une couche organique auto-assemblée et ensuite un suivi de l’interaction spécifique entre deux brins d’ADN complémentaires a été effectué. Le manuscrit s’achève par une analyse des aspects plus complexes liés à la nature peu multimodale des fibres présentes dans le faisceau. La théorie des guides d’ondes est alors utilisée pour expliquer l’influence du caractère modal de la propagation de la lumière sur les réponses des fibres optiques. / This Ph.D. thesis focuses on the design of an original “lab-on-fiber” tool for remote, label-free in vivo molecular analysis that could be dedicated in the future to endoscopic diagnosis. Our approach is based on functionalized microstructured optical fiber bundles. When appropriately designed and covered by a gold layer, those fibers exhibit interesting plasmonic properties. First, the numerical model used to reach a better understanding of the physical phenomena involved in the optimization of the sensor’s sensitivity is explained. The simulations based on ray optics were then used to optimize the fiber tip geometry and gold coating thickness to enhance the analytical performances and ultimately allow biochemical detections. The fabrication process of the sensor is then explained going from the chemical etching done by the ISM team (Bordeaux) to the metallization of the tips performed at the CEA Grenoble. A comparison between theoretical and experimental behaviors is then conducted to assess the influence of the heterogeneity of both the gold deposit and the etched surfaces on the optical sensitivity. Afterwards, we take advantage of those optical properties to perform remote biochemical analysis. This was achieved in two steps: we first proved that our sensor was sensitive to local optical index variations by detecting the adsorption of a thin self-assembled organic layer and ultimately a specific interaction between two complementary DNA strands was monitored. The last part of this work tackles the more difficult aspects of the few-modes fibers composing the bundle. Waveguide theory is then used to explain the influence of the modal characteristics of light propagation on the optical fibers responses.

Choy Man Ting. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 66-69). / Abstracts in English and Chinese. / Acknowledgments --- p.ii / Abstract --- p.v / Table of Contents --- p.vii / List of figures --- p.viii / Chapter Chapter 1 --- p.12 / Chapter 1.1 --- OBS Network Architecture --- p.3 / Chapter 1.2 --- Offset Time and Reservation Schemes --- p.5 / Chapter 1.3 --- Research Objectives --- p.7 / Chapter 1.4 --- Overview --- p.8 / Chapter Chapter 2 --- p.9 / Chapter 2.1 --- WDM crossbar architectures --- p.9 / Chapter 2.2 --- Switch Based on Optical Crossbars --- p.10 / Chapter 2.3 --- Switch Based on Wavelength Grating Routers --- p.11 / Chapter Chapter 3 --- p.14 / Chapter 3.1 --- Basics of Dual Shuffle Exchange Network --- p.14 / Chapter 3.2 --- Dual Shuffle-exchange Network --- p.16 / Chapter 3.3 --- Proposed Architecture based on DSN --- p.19 / Chapter 3.4 --- Analysis on blocking due to output contention --- p.20 / Chapter 3.5 --- Implementation issues on the 4x4 switching module --- p.23 / Chapter 3.6 --- Analysis: Non-blocking versus banyan --- p.25 / Chapter Chapter 4 --- p.30 / Chapter 4.1 --- First Scheme --- p.30 / Chapter 4.2 --- Simulation on the first scheme --- p.33 / Chapter 4.3 --- Second Scheme: Tunable wavelength converter --- p.37 / Chapter 4.4 --- Third Scheme: Route to specific wavelength port --- p.42 / Chapter 4.5 --- Analysis on blocking due to insufficient stages --- p.46 / Chapter Chapter 5 --- p.49 / Chapter 5.1 --- Delay analysis of DSN --- p.49 / Chapter 5.2 --- Vertical Expansion --- p.51 / Chapter 5.3 --- Simulation results on vertical expansion --- p.52 / Chapter 5.4 --- Building DSN with 8x8 MEMS switches --- p.54 / Chapter 5.5 --- Prove of the proposed Quarter shuffle network --- p.56 / Chapter 5.6 --- Comparison between Quarter shuffle and doubled links approaches --- p.58 / Chapter Chapter 6 --- p.64 / Conclusion --- p.64 / Bibliography --- p.66

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / by Louis Andrew Nagode. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaf 73. / by Oliver Chukwudi Ibe. / M.S.

This thesis presents a light scattering-based method for biomarker detection, which could potentially be used for the quantification of multiple biomarkers specific to B-cell malignancies. This method uses fabricated gold nanoparticle probes to amplify inelastic light scattering in a process referred to as surface-enhanced Raman scattering. These gold nanoparticle probes were conjugated to antibodies for specific and targeted molecular binding. The spectrum of the amplified inelastic light scattering was detected using a spectrometer and a detector. To detect the light scattering signal from the gold nanoparticle probes, several commercial Raman spectrometer instruments were evaluated. Initial results from these evaluations are presented in this thesis. After system evaluation, a custom Raman microscope system was designed, built, and tested. This system was used for the development of a surface-enhanced Raman spectroscopy-based immunoassay. The development of this assay confirms the successful design of gold nanoparticle probes for the specific targeting and detection of immunoglobulins. The immunoassay also shows promise for the simultaneous detection of multiple biomarkers specific to B-cell malignancies.

The current popularity of WLANs is a testament primarily to their convenience, cost efficiency and ease of integration. Even now the demand for high data rate wireless communications has increased fourfold as consumers demand better multimedia communications over the wireless medium. The next generation of high speed WLANs is expected to meet this increased demand for capacity coupled with high performance and spectral efficiency. The current generation of WLANs utilizes Orthogonal Frequency Division Multiplexing (OFDM) modulation. The next generation of WLAN standards can be made possible either by developing a different modulation technique or combining legacy OFDM with Multiple Input Multiple Output (MIMO) systems to create MIMO-OFDM systems. This dissertation presents two different basis technologies for the next generation of high speed WLANs: OWSS and MIMO-STC-OFDM. OWSS, or Orthogonal Wavelet Division Multiplexed - Spread Spectrum is a new class of wavelet pulses and a corresponding signaling system which has significant advantages over current signaling schemes like OFDM. In this dissertation, CSMA/CA is proposed as the protocol for full data rate multiplexing at the MAC layer for OWSS. The excellent spectral characteristics of the OWSS signal is also studied and simulations show that passband spectrum enjoys a 30-40% bandwidth advantage over OFDM. A novel pre-distortion scheme was developed to compensate for the passband PA non-linearity. Finally for OWSS, the fundamental limits of its system performance were also explored using a multi-level matrix formulation. Simulation results on a 108 Mbps OWSS WLAN system demonstrate the excellent effectiveness of this theory and prove that OWSS is capable of excellent performance and high spectral efficiency in multipath channels. This dissertation also presents a novel MIMO-STC-OFDM system which targets data rates in excess of 100 Mbps and at the same time achieve both high spectral efficiency and high performance. Simulation results validate the superior performance of the new system over multipath channels. Finally as channel equalization is critical in MIMO systems, a highly efficient time domain channel estimation formulation for this new system is also presented. In summary, both OWSS and MIMO-STC-OFDM appear to be excellent candidate technologies for next generation of high speed WLANs.