The Experts below are selected from a list of 192 Experts worldwide ranked by ideXlab platform

Anders Larsson - One of the best experts on this subject based on the ideXlab platform.

  • Optimum Damping Level for High-Speed Large Signal VCSEL modulation
    2017
    Co-Authors: Emanuel P Haglund, Petter Westbergh, Johan S Gustavsson, Anders Larsson
    Abstract:

    The commercial optical interconnects used in datacenters and high performance computers have recently been pushed to data rates of 25-28 Gbps. Near future standards will require even higher data rates and further work to increase the speed is therefore necessary. Typically the 850 nm vertical-cavity surface-emitting laser (VCSEL) is employed as light source in such optical interconnects, due to its low-cost fabrication and excellent high-speed properties at low drive currents. Previously, we have shown that a reduction of the Damping of the VCSEL small signal modulation response can increase the modulation bandwidth (BW) and that there exists an Optimum Damping for maximum BW. This allowed us to demonstrate a record-high small signal modulation BW of 28 GHz and error-free [bit error rate (BER)

  • Optimum Damping level for high speed large signal vcsel modulation
    Optics and Photonics in Sweden 11-12 Nov. 2014, 2014
    Co-Authors: Emanuel P Haglund, Petter Westbergh, Johan S Gustavsson, Anders Larsson
    Abstract:

    The commercial optical interconnects used in datacenters and high performance computers have recently been pushed to data rates of 25-28 Gbps. Near future standards will require even higher data rates and further work to increase the speed is therefore necessary. Typically the 850 nm vertical-cavity surface-emitting laser (VCSEL) is employed as light source in such optical interconnects, due to its low-cost fabrication and excellent high-speed properties at low drive currents. Previously, we have shown that a reduction of the Damping of the VCSEL small signal modulation response can increase the modulation bandwidth (BW) and that there exists an Optimum Damping for maximum BW. This allowed us to demonstrate a record-high small signal modulation BW of 28 GHz and error-free [bit error rate (BER) <10^-12] transmission up to 57 Gbps. However, the Optimum Damping for maximum BW does not necessarily equate to the Damping that produces the highest quality eye and best receiver sensitivity under large signal modulation. Recently we showed that the Optimum Damping for large signal modulation is dependent on the data rate. The Damping (quantified by the K-factor) should be tuned to yield sufficiently fast rise time, high BW, and low timing jitter to produce a clear eye opening. At low data rates, the BW requirement is low and one can afford to use a low bias and a large Damping which results in a low timing jitter, whereas an increase of the bias and a reduction of the Damping is necessary at higher data rates to achieve sufficiently fast rise time and large BW to keep the eye open. This induces more timing jitter. The dependence of Optimum Damping on data rate was illustrated by BER measurements, which showed that the most damped VCSELs achieved the best receiver sensitivity at 10 Gbps, whereas a slightly less damped VCSEL achieved the best receiver sensitivity at 40 Gbps. Using a too low Damping will induce too much timing jitter yielding an unusable high BER.

Fook Hoong Choo - One of the best experts on this subject based on the ideXlab platform.

  • Exploring Inherent Damping Characteristic of LCL-Filters for Three-Phase Grid-Connected Voltage Source Inverters
    IEEE Transactions on Power Electronics, 2012
    Co-Authors: Yi Tang, Peng Wang, Fook Hoong Choo
    Abstract:

    This paper investigates the inherent Damping characteristic of LCL- filters for three-phase grid-connected voltage source inverters. Specifically, it is found that when the converter-side current is used for implementing the feedback control, there will be an inherent Damping term embedded in the control loop, which can neutralize the resonance introduced by LCL- filters. Theoretical analysis is then presented to suggest a general design guideline for choosing values of grid- and converter-side inductors, so that Optimum Damping can be naturally achieved by solely using converter current control, doing away with active Damping, passive Damping, or complex state observer. In cases where the design criterion is not fulfilled, the Damping information contained in the converter current is extracted by a second-order notch filter, and then processed by a compensation gain to tune the system Damping factor. The proposed compensation strategy requires no additional hardware and it will not cause an overmodulation problem due to its free of fundamental component. Both simulation and experimental results are finally provided to validate the theoretical findings developed in this paper.

  • Exploring inherent Damping characteristic of LCL-filters for three-phase grid-connected voltage source inverters
    2010 IEEE Energy Conversion Congress and Exposition, 2010
    Co-Authors: Yi Tang, Peng Wang, Fook Hoong Choo
    Abstract:

    This paper investigates the inherent Damping characteristic of LCL-filters for three-phase grid-connected voltage source inverters (VSIs). Specifically, it is found that there is an inherent Damping term embedded in the feedback loop when converter current is used for implementing closed-loop control. This additional Damping term can indeed neutralize the resonance introduced by LCL-filters, and thus giving rise to a more stable system than that of grid current feedback control. In this case, only one set of current sensors is required to stabilize the system, doing away with passive Damping, active Damping or complex state observer. Theoretical analysis is then presented and lead to a general design guideline, which suggests a way of choosing the values of grid- and converter-side inductors, so that Optimum Damping can be naturally achieved by solely using converter current control. In the case when this design criterion is not fulfilled, a simple compensation method is also proposed to tune the Damping factor. Both simulation and experimental results are finally provided to validate the theoretical findings developed in this paper.

Emanuel P Haglund - One of the best experts on this subject based on the ideXlab platform.

  • Optimum Damping Level for High-Speed Large Signal VCSEL modulation
    2017
    Co-Authors: Emanuel P Haglund, Petter Westbergh, Johan S Gustavsson, Anders Larsson
    Abstract:

    The commercial optical interconnects used in datacenters and high performance computers have recently been pushed to data rates of 25-28 Gbps. Near future standards will require even higher data rates and further work to increase the speed is therefore necessary. Typically the 850 nm vertical-cavity surface-emitting laser (VCSEL) is employed as light source in such optical interconnects, due to its low-cost fabrication and excellent high-speed properties at low drive currents. Previously, we have shown that a reduction of the Damping of the VCSEL small signal modulation response can increase the modulation bandwidth (BW) and that there exists an Optimum Damping for maximum BW. This allowed us to demonstrate a record-high small signal modulation BW of 28 GHz and error-free [bit error rate (BER)

  • Optimum Damping level for high speed large signal vcsel modulation
    Optics and Photonics in Sweden 11-12 Nov. 2014, 2014
    Co-Authors: Emanuel P Haglund, Petter Westbergh, Johan S Gustavsson, Anders Larsson
    Abstract:

    The commercial optical interconnects used in datacenters and high performance computers have recently been pushed to data rates of 25-28 Gbps. Near future standards will require even higher data rates and further work to increase the speed is therefore necessary. Typically the 850 nm vertical-cavity surface-emitting laser (VCSEL) is employed as light source in such optical interconnects, due to its low-cost fabrication and excellent high-speed properties at low drive currents. Previously, we have shown that a reduction of the Damping of the VCSEL small signal modulation response can increase the modulation bandwidth (BW) and that there exists an Optimum Damping for maximum BW. This allowed us to demonstrate a record-high small signal modulation BW of 28 GHz and error-free [bit error rate (BER) <10^-12] transmission up to 57 Gbps. However, the Optimum Damping for maximum BW does not necessarily equate to the Damping that produces the highest quality eye and best receiver sensitivity under large signal modulation. Recently we showed that the Optimum Damping for large signal modulation is dependent on the data rate. The Damping (quantified by the K-factor) should be tuned to yield sufficiently fast rise time, high BW, and low timing jitter to produce a clear eye opening. At low data rates, the BW requirement is low and one can afford to use a low bias and a large Damping which results in a low timing jitter, whereas an increase of the bias and a reduction of the Damping is necessary at higher data rates to achieve sufficiently fast rise time and large BW to keep the eye open. This induces more timing jitter. The dependence of Optimum Damping on data rate was illustrated by BER measurements, which showed that the most damped VCSELs achieved the best receiver sensitivity at 10 Gbps, whereas a slightly less damped VCSEL achieved the best receiver sensitivity at 40 Gbps. Using a too low Damping will induce too much timing jitter yielding an unusable high BER.

Yi Tang - One of the best experts on this subject based on the ideXlab platform.

  • Exploring Inherent Damping Characteristic of LCL-Filters for Three-Phase Grid-Connected Voltage Source Inverters
    IEEE Transactions on Power Electronics, 2012
    Co-Authors: Yi Tang, Peng Wang, Fook Hoong Choo
    Abstract:

    This paper investigates the inherent Damping characteristic of LCL- filters for three-phase grid-connected voltage source inverters. Specifically, it is found that when the converter-side current is used for implementing the feedback control, there will be an inherent Damping term embedded in the control loop, which can neutralize the resonance introduced by LCL- filters. Theoretical analysis is then presented to suggest a general design guideline for choosing values of grid- and converter-side inductors, so that Optimum Damping can be naturally achieved by solely using converter current control, doing away with active Damping, passive Damping, or complex state observer. In cases where the design criterion is not fulfilled, the Damping information contained in the converter current is extracted by a second-order notch filter, and then processed by a compensation gain to tune the system Damping factor. The proposed compensation strategy requires no additional hardware and it will not cause an overmodulation problem due to its free of fundamental component. Both simulation and experimental results are finally provided to validate the theoretical findings developed in this paper.

  • Exploring inherent Damping characteristic of LCL-filters for three-phase grid-connected voltage source inverters
    2010 IEEE Energy Conversion Congress and Exposition, 2010
    Co-Authors: Yi Tang, Peng Wang, Fook Hoong Choo
    Abstract:

    This paper investigates the inherent Damping characteristic of LCL-filters for three-phase grid-connected voltage source inverters (VSIs). Specifically, it is found that there is an inherent Damping term embedded in the feedback loop when converter current is used for implementing closed-loop control. This additional Damping term can indeed neutralize the resonance introduced by LCL-filters, and thus giving rise to a more stable system than that of grid current feedback control. In this case, only one set of current sensors is required to stabilize the system, doing away with passive Damping, active Damping or complex state observer. Theoretical analysis is then presented and lead to a general design guideline, which suggests a way of choosing the values of grid- and converter-side inductors, so that Optimum Damping can be naturally achieved by solely using converter current control. In the case when this design criterion is not fulfilled, a simple compensation method is also proposed to tune the Damping factor. Both simulation and experimental results are finally provided to validate the theoretical findings developed in this paper.

R S Jangid - One of the best experts on this subject based on the ideXlab platform.

  • Optimum parameters of tuned mass damper for damped main system
    Structural Control & Health Monitoring, 2007
    Co-Authors: S V Bakre, R S Jangid
    Abstract:

    A tuned mass damper (TMD) is a device consisting of small damped spring–mass system attached to a vibrating main system in order to attenuate any undesirable vibrations. In this paper, Optimum parameters of TMD system attached to a viscously damped single degree-of-freedom main system are derived for various combinations of excitation and response parameters. The excitation applied to the main system consists of external force and base acceleration modelled as Gaussian white-noise random process. Using numerical searching technique, the Optimum Damping and tuning frequency ratio of the TMD are obtained for minimization of various mean square responses such as relative displacement, velocity of main mass and force transmitted to the support. The Optimum parameters of the TMD system and the corresponding response quantities are obtained for different Damping ratios of the main system and the mass ratios of the TMD system. Explicit formulae for damper Damping, tuning frequency and the corresponding minimized response are then derived using curve-fitting technique that can be conveniently used for applications in dynamical systems. The error in these expressions is found to be negligible and hence these expressions are convenient for use in damped single degree-of-freedom main system. The Optimum Damping ratio of the TMD is not much influenced by the Damping of the main system. However, the Optimum tuning frequency of TMD is significantly affected by the Damping of main system. Lastly, a comparison of the Optimum Damping and tuning frequency of the TMD under filtered white-noise and white-noise excitation is also made. Copyright © 2006 John Wiley & Sons, Ltd.

  • Optimum Damping in a non linear base isolation system
    Journal of Sound and Vibration, 1996
    Co-Authors: R S Jangid
    Abstract:

    Abstract Optimum isolation Damping for minimum acceleration of a base-isolated structure subjected to earthquake ground excitation is investigated. The stochastic model of theEl-Centro1940 earthquake, which preserves the non-stationary evolution of amplitude and frequency content of ground motion, is used as an earthquake excitation. The base isolated structure consists of a linear flexible shear type multi-storey building supported on a base isolation system. The resilient-friction base isolator (R-FBI) is considered as an isolation system. The non-stationary stochastic response of the system is obtained by the time dependent equivalent linearization technique as the force-deformation of the R-FBI system is non-linear. The Optimum Damping of the R-FBI system is obtained under important parametric variations; i.e., the coefficient of friction of the R-FBI system, the period and Damping of the superstructure; the effective period of base isolation. The criterion selected for optimality is the minimization of the top floor root mean square (r.m.s.) acceleration. It is shown that the above parameters have significant effects on Optimum isolation Damping.