The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Kin-lu Wong - One of the best experts on this subject based on the ideXlab platform.
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Analysis of a cylindrical-rectangular microstrip structure with an airgap
IEEE Transactions on Microwave Theory and Techniques, 1994Co-Authors: Kin-lu Wong, Yuan-tung ChengAbstract:The resonance problem of the cylindrical-rectangular microstrip structure with an airgap between the substrate layer and the ground conducting cylinder is studied by using a rigorous full-wave approach and a moment method calculation. The resonance condition is satisfied by complex resonant frequencies, which provide the information of resonant frequency and half-Power Bandwidth of the structure. Numerical results indicate that, with the increasing of the airgap thickness, the half-Power Bandwidth of the structure at the efficient radiating mode of HE/sub 0.1/ is considerably increased, which improves the narrow Bandwidth characteristics of microstrip structures. Details of the numerical results, including the results for the planar rectangular microstrip structure with an airgap, are presented and analyzed.
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Resonance in a spherical-circular microstrip structure with an airgap
IEEE Transactions on Microwave Theory and Techniques, 1993Co-Authors: Kin-lu Wong, Hong-twu ChenAbstract:The resonance problem of the spherical-circular microstrip structure with an airgap between the substrate layer and the ground conducting sphere is studied by using a rigorous Green's function formulation in the spectral domain and Galerkin's moment method calculation. Complex resonant frequencies are obtained in this study, which provide the resonant frequencies and half-Power Bandwidth of the structure. From the numerical results, it is found that with the increasing of the airgap thickness, the half-Power Bandwidth of the structure is considerably increased. This improves the low-Bandwidth characteristics of microstrip structures. Details of the numerical results are presented and discussed.
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Resonance in a Spherical-Circular Microstrip
1991Co-Authors: Kin-lu Wong, Hong-m ChenAbstract:ibstruct-The resonance problem of the spherical-circular microstrip structure with an airgap between the substrate layer and the ground conducting sphere is studied by using a rigorous Green's function formulat ion in the spectral domain and Galerkin's moment method calculation. Crmplex resonant frequencies are obtained in this study, which provide thv resonant frequencies and half-Power Bandwidth of the structure. Frm the numerical results, it is found that with the increasing of the airga 3 thickness, the half-Power Bandwidth of the structure is considerably inc reased. This improves the low-Bandwidth characteristics of microstrip structures. Details of the numerical results are presented and discussed.
Ozgur Oyman - One of the best experts on this subject based on the ideXlab platform.
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Power-Bandwidth Tradeoff in Multiuser Relay Channels with Opportunistic Scheduling
arXiv: Information Theory, 2008Co-Authors: Ozgur Oyman, Moe Z. WinAbstract:The goal of this paper is to understand the key merits of multihop relaying techniques jointly in terms of their energy efficiency and spectral efficiency advantages in the presence of multiuser diversity gains from opportunistic (i.e., channel-aware) scheduling and identify the regimes and conditions in which relay-assisted multiuser communication provides a clear advantage over direct multiuser communication. For this purpose, we use Shannon-theoretic tools to analyze the tradeoff between energy efficiency and spectral efficiency (known as the Power-Bandwidth tradeoff) over a fading multiuser relay channel with $K$ users in the asymptotic regime of large (but finite) number of users (i.e., dense network). Benefiting from the extreme-value theoretic results of \cite{Oyman_isit07}, we characterize the Power-Bandwidth tradeoff and the associated energy and spectral efficiency measures of the Bandwidth-limited high signal-to-noise ratio (SNR) and Power-limited low SNR regimes, and utilize them in investigating the large system behavior of the multiuser relay channel as a function of the number of users and physical channel SNRs. Our analysis results in very accurate closed-form formulas in the large (but finite) $K$ regime that quantify energy and spectral efficiency performance, and provides insights on the impact of multihop relaying and multiuser diversity techniques on the Power-Bandwidth tradeoff.
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Power-Bandwidth tradeoff in multiuser relay channels with opportunistic scheduling
2008 46th Annual Allerton Conference on Communication Control and Computing, 2008Co-Authors: Ozgur Oyman, Moe Z. WinAbstract:The goal of this paper is to understand the key merits of multihop relaying techniques jointly in terms of their energy efficiency and spectral efficiency advantages in the presence of multiuser diversity gains from opportunistic (i.e., channel-aware) scheduling and identify the regimes and conditions in which relay-assisted multiuser communication provides a clear advantage over direct multiuser communication. For this purpose, we use Shannon-theoretic tools to analyze the tradeoff between energy efficiency and spectral efficiency (known as the Power-Bandwidth tradeoff) over a fading multiuser relay channel with K users in the asymptotic regime of large (but finite) number of users (i.e., dense network). Benefiting from the extreme-value theoretic results of [1], we characterize the Power-Bandwidth tradeoff and the associated energy and spectral efficiency measures of the Bandwidth-limited high signal-to-noise ratio (SNR) and Power-limited low SNR regimes, and utilize them in investigating the large system behavior of the multiuser relay channel as a function of the number of users and physical channel SNRs. Our analysis results in very accurate closed-form formulas in the large (but finite) K regime that quantify energy and spectral efficiency performance, and provides insights on the impact of multihop relaying and multiuser diversity techniques on the Power-Bandwidth tradeoff.
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Power Bandwidth tradeoff in dense multi antenna relay networks
arXiv: Information Theory, 2007Co-Authors: Ozgur Oyman, Arogyaswami PaulrajAbstract:We consider a dense fading multi-user network with multiple active multi-antenna source-destination pair terminals communicating simultaneously through a large common set of $K$ multi-antenna relay terminals in the full spatial multiplexing mode. We use Shannon-theoretic tools to analyze the tradeoff between energy efficiency and spectral efficiency (known as the Power- Bandwidth tradeoff) in meaningful asymptotic regimes of signal-to-noise ratio (SNR) and network size. We design linear distributed multi-antenna relay beamforming (LDMRB) schemes that exploit the spatial signature of multi-user interference and characterize their Power-Bandwidth tradeoff under a system wide Power constraint on source and relay transmissions. The impact of multiple users, multiple relays and multiple antennas on the key performance measures of the high and low SNR regimes is investigated in order to shed new light on the possible reduction in Power and Bandwidth requirements through the usage of such practical relay cooperation techniques. Our results indicate that point-to-point coded multi-user networks supported by distributed relay beamforming techniques yield enhanced energy efficiency and spectral efficiency, and with appropriate signaling and sufficient antenna degrees of freedom, can achieve asymptotically optimal Power-Bandwidth tradeoff with the best possible (i.e., as in the cutset bound) energy scaling of $K^{-1}$ and the best possible spectral efficiency slope at any SNR for large number of relay terminals.
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Power-Bandwidth Tradeoff in Dense Multi-Antenna Relay Networks
IEEE Transactions on Wireless Communications, 2007Co-Authors: Ozgur Oyman, Arogyaswami PaulrajAbstract:We consider a dense fading multi-user network with multiple active multi-antenna source-destination pair terminals communicating simultaneously through a large common set of K multi-antenna relay terminals in the full spatial multiplexing mode. We use Shannon-theoretic tools to analyze the tradeoff between energy efficiency and spectral efficiency (known as the Power-Bandwidth tradeoff) in meaningful asymptotic regimes of signal-to-noise ratio (SNR) and network size. We design linear distributed multi-antenna relay beamforming (LDMRB) schemes that exploit the spatial signature of multi-user interference and characterize their Power-Bandwidth tradeoff under a system-wide Power constraint on source and relay transmissions. The impact of multiple users, multiple relays and multiple antennas on the key performance measures of the high and low SNR regimes is investigated in order to shed new light on the possible reduction in Power and Bandwidth requirements through the usage of such practical relay cooperation techniques. Our results indicate that point-to-point coded multi-user networks supported by distributed relay beamforming techniques yield enhanced energy efficiency and spectral efficiency, and with appropriate signaling and sufficient antenna degrees of freedom, can achieve asymptotically optimal Power-Bandwidth tradeoff with the best possible (i.e., as in the cutset bound) energy scaling of K-1 and the best possible spectral efficiency slope at any SNR for large number of relay terminals. Furthermore, our results help to identify the role of interference cancellation capability at the relay terminals on realizing the optimal Power- Bandwidth tradeoff; and show how relaying schemes that do not attempt to mitigate multi-user interference, despite their optimal capacity scaling performance, could yield a poor Power- Bandwidth tradeoff.
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non ergodic Power Bandwidth tradeoff in linear multi hop networks
International Symposium on Information Theory, 2006Co-Authors: Ozgur Oyman, Sumeet SandhuAbstract:The prior work on Power-Bandwidth tradeoff analysis in fading environments has assumed the ergodicity of the channel statistics along with infinite code block-lengths, which allow defining energy and spectral efficiency measures as a function of the Shannon capacity. We generalize the Power-Bandwidth tradeoff analysis framework to draw insights for a specific form communication under a non-ergodic fading model. In particular, we study the Power-Bandwidth tradeoff in a one-dimensional slow-fading multi-hop relay network. We characterize the impact of multi-hopping on the statistical properties of the end-to-end conditional mutual information (conditioned on the specific values of the channel fading parameters and therefore treated as a random variable) and on the energy and spectral efficiency measures computed from the conditional mutual information. Our non-ergodic Power-Bandwidth tradeoff analysis focuses on two asymptotic regimes: (i) Power-limited (low signal-to-noise ratio (SNR)) regime and (ii) Bandwidth-limited (high SNR) regime. In both regimes, we investigate the performance of open-loop (fixed-rate) and closed-loop (rate-adaptive) multi-hop relaying mechanisms in terms of their Power-band width tradeoffs and end-to-end outage probabilities. Interestingly, our analysis reveals the new notion of "multi-hop diversity" toward enhancing link reliability in diversity-limited fading environments
James A. Lott - One of the best experts on this subject based on the ideXlab platform.
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Power-Bandwidth-efficiency trade-offs of septuple VCSEL arrays
2020 IEEE Photonics Conference (IPC), 2020Co-Authors: Nasibeh Haghighi, Philip Moser, James A. LottAbstract:Compact groups of seven electrically-parallel, optically uncoupled, top-surface-emitting 980 nm vertical-single-cavity surface-emitting lasers arranged in a unique interconnected honeycomb pattern exhibit record concurrent combinations of large optical output Power (70 to 100 mW), wall plug efficiency, and small-signal modulation Bandwidth (15 to 21 GHz).
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Power-Bandwidth Trade-Offs of 25 Gbps Triple VCSEL Arrays
2019 IEEE Photonics Conference (IPC), 2019Co-Authors: Nasibeh Haghighi, Philip Moser, Sarah Cwalina, Martin Zorn, James A. LottAbstract:Compact groups of three electrically-parallel 980 nm oxide-confined vertical-single-cavity surface-emitting lasers via on-wafer probing exhibit record room temperature small-signal modulation Bandwidths of 20 to 25 GHz and corresponding large optical output Powers of 60 to 20 mW, respectively, and back-to-back 25 Gbps error-free data transmission.
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Power, Bandwidth, and Efficiency of Single VCSELs and Small VCSEL Arrays
IEEE Journal of Selected Topics in Quantum Electronics, 2019Co-Authors: Nasibeh Haghighi, Philip Moser, James A. LottAbstract:Single-emitter vertical-cavity surface-emitting lasers (VCSELs) and multiple-emitter VCSEL arrays designed for emission at 980 nm, and with large oxide aperture diameters ( φ ) from ∼10.5 to 33.5 μm and with φ of ∼7.5 μm that are configured in three-emitter and seven-emitter electrically parallel triangular and hexagonal arrays, respectively, have record Bandwidths and optical output Powers for VCSELs with such large cumulative emitting areas. We demonstrate room temperature (RT) maximum small-signal modulation Bandwidths ( f 3dBmax) of 26.6 to 18.6 GHz with corresponding continuous wave (CW) optical output Powers ( L ) of 16.2 and 47 mW for VCSELs with φ ∼13.5 and 33.5 μm, respectively. For parallel 980 nm triple and septuple arrays with φ ∼7.5 μm for each VCSEL, we demonstrate RT f 3dBmax of 25.5 and 24.8 GHz with corresponding CW L of 22.7 and 50.1 mW, respectively. We perform a comparative analysis of the RT results, which consist of standard static light output Power–current–voltage ( LIV ) characteristics to determine the typical VCSEL figures-of-merit including wall plug efficiency (WPE), LI slope efficiency, spectral emission versus current ( I ), and small-signal frequency response curves. We examine the tradeoffs in optical output Power, small-signal modulation Bandwidth, and WPE for the various VCSEL designs, and find that while the combination of f 3dBmax and L are record values for single VCSELs and VCSEL arrays, these parameters fall off as the cumulative VCSEL array area increases to emit higher overall optical Power.
A. Gusmao - One of the best experts on this subject based on the ideXlab platform.
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A class of signal processing algorithms for good Power/Bandwidth tradeoffs with OFDM transmission
2000 IEEE International Symposium on Information Theory (Cat. No.00CH37060), 1Co-Authors: Rui Dinis, A. GusmaoAbstract:This paper presents a wide class of signal processing algorithms which employs a nonlinear operation in the time domain and is capable of providing good Power/Bandwidth tradeoffs with OFDM transmission. A suitable analytical approach is proposed for efficiently evaluating the performance within this class of algorithms, and several performance results are shown and discussed in detail.
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ICC - Signal processing schemes for Power/Bandwidth efficient OFDM transmission with conventional or LINC transmitter structures
ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240), 1Co-Authors: Rui Dinis, A. GusmaoAbstract:This paper considers a wide class of digital signal processing schemes, previously proposed by the authors, which combines a nonlinear operation in the time domain and a linear operation in the frequency domain, so as to reduce the envelope fluctuations and allow good Power/Bandwidth tradeoffs with OFDM transmission; it also considers both conventional and two-branch, LINC (linear amplification with nonlinear components) transmitter structures. The paper uses the ideas behind that class so as to show that it includes "peak cancellation" schemes, such as that proposed by other authors, and also in order to derive signal processing schemes for LINC decomposition purposes, while keeping low out-of-band radiation levels. The paper addresses the statistical characterization of the frequency domain blocks effectively transmitted, so as to evaluate by analytical means, in a unified manner, either those peak cancellation schemes (to be used within a conventional transmitter structure) or the signal processing schemes to be employed within a LINC transmitter structure. A set of numerical results, which have been obtained with the help of this analytical method, is presented and discussed.
Hong-twu Chen - One of the best experts on this subject based on the ideXlab platform.
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Resonance in a spherical-circular microstrip structure with an airgap
IEEE Transactions on Microwave Theory and Techniques, 1993Co-Authors: Kin-lu Wong, Hong-twu ChenAbstract:The resonance problem of the spherical-circular microstrip structure with an airgap between the substrate layer and the ground conducting sphere is studied by using a rigorous Green's function formulation in the spectral domain and Galerkin's moment method calculation. Complex resonant frequencies are obtained in this study, which provide the resonant frequencies and half-Power Bandwidth of the structure. From the numerical results, it is found that with the increasing of the airgap thickness, the half-Power Bandwidth of the structure is considerably increased. This improves the low-Bandwidth characteristics of microstrip structures. Details of the numerical results are presented and discussed.