The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform
Mikhail A. Vorontsov - One of the best experts on this subject based on the ideXlab platform.
-
stochastic parallel gradient descent technique for high resolution wave front Phase Distortion correction
Journal of The Optical Society of America A-optics Image Science and Vision, 1998Co-Authors: Mikhail A. Vorontsov, V P SivokonAbstract:A new optimization technique, stochastic parallel-gradient descent, is applied for high-resolution adaptive wave-front correction. A performance criterion for parallel-perturbation-based algorithms is introduced and applied to optimize adaptive system architecture. We present numerical simulation results for an adaptive imaging system based on the stochastic parallel-perturbation technique, along with experimental results obtained for a white-light adaptive imaging system with 37 control channels. An adaptive system with a self-organized (adaptive) control channel hierarchy is introduced and analyzed.
-
High-resolution Phase Distortion compensation in adaptive interferometers
Adaptive Optical System Technologies, 1998Co-Authors: Michael K. Giles, Mikhail A. Vorontsov, Rensheng Dou, Viktor P. SivokonAbstract:High resolution adaptive Phase Distortion suppression was experimentally demonstrated for laser interferometers using a liquid crystal television as a Phase modulator and an opto-electronic feedback loop. The experiments were carried out for both amplitude division and rotational shear types of interferometers. The suggested iterative control algorithm is based solely on interference pattern information. The results of numerical simulations of a high resolution adaptive system based on rotational shear type interferometers show the system's potential for atmospheric turbulence Phase Distortion suppression.
-
High-resolution adaptive Phase Distortion suppression based solely on intensity information
Journal of the Optical Society of America A, 1998Co-Authors: Viktor P. Sivokon, Mikhail A. VorontsovAbstract:New control algorithms for an adaptive system with high-resolution piston-type wave-front corrector and optoelectronic feedback that do not require Phase information are introduced and analyzed. Numerical simulations of adaptive system performance in the presence of Phase Distortions described using several common Phase fluctuation spectrums demonstrate the effectiveness of this approach. An adaptive optical system having two separate feedback loops for compensation of large- and small-scale Phase Distortions is studied. Spatiotemporal instabilities that can occur in high-resolution adaptive systems were observed in numerical simulations.
-
Iterative technique for high-resolution Phase Distortion compensation in adaptive interferometers
Optical Engineering, 1997Co-Authors: Rensheng Dou, Mikhail A. Vorontsov, Viktor P. Sivokon, Michael K. GilesAbstract:High-resolution adaptive Phase Distortion suppression is ex- perimentally demonstrated for laser interferometers using a liquid crystal television as a Phase modulator and an optoelectronic feedback loop. The experiments are carried out for both amplitude division (Mach- Zehnder) and rotational shear types of interferometers. The suggested iterative control algorithm is based solely on interference pattern infor- mation. The results of numerical simulations of a high-resolution adap- tive system based on rotational shear type interferometers show the sys- tem's potential for atmospheric turbulence Phase Distortion suppression.
-
adaptive Phase Distortion correction based on parallel gradient descent optimization
Optics Letters, 1997Co-Authors: Mikhail A. Vorontsov, Gary W Carhart, Jennifer C RicklinAbstract:We describe an adaptive wave-front control technique based on a parallel stochastic perturbation method that can be applied to a general class of adaptive-optical system. The efficiency of this approach is analyzed numerically and experimentally by use of a white-light adaptive-imaging system with an extended source. To create and compensate for static Phase Distortions, we use 127-element liquid-crystal Phase modulators. Results demonstrate that adaptive wave-front correction by a parallel-perturbation technique can significantly improve image quality.
John H Booske - One of the best experts on this subject based on the ideXlab platform.
-
Mechanisms for Phase Distortion in a traveling wave tube.
Physical review. E Statistical nonlinear and soft matter physics, 2004Co-Authors: John G. Wohlbier, John H BooskeAbstract:We present a view of the physics of Phase Distortion in a traveling wave tube (TWT) based on unique insights afforded by the MUSE models of a TWT [IEEE Trans. Plasma Sci. 30, 1063 (2002)]]. The conclusion, supported by analytic theory and simulations, is that prior to gain compression Phase Distortion is due to harmonic frequencies in the electron beam and the resulting "intermodulation" frequency at the fundamental, and not the often cited "slowing down of electrons in the electron beam." We draw these conclusions based on MUSE simulations that allow explicit control of electron beam frequency content, an analytic solution to the S-MUSE model [IEEE Trans. Plasma Sci. 30, 1063 (2002)]] that reveals that Phase Distortion is due to the fact that the fundamental frequency is an intermodulation product of itself, and large signal LATTE [IEEE Trans. Plasma Sci. 30, 1063 (2002)]] simulations that are modified to remove the effect of the slowing down of electrons in the electron beam. As applications of the theory we compare S-MUSE simulations to an amplitude Phase model using the analytic Phase transfer curve, we study dependence of Phase Distortion on circuit dispersion and electron beam parameters at the second harmonic with large signal LATTE simulations for narrow and wide band TWT designs, and we consider the Phase Distortion theory in the context of TWT linearization.
-
Mechanisms for Phase Distortion in a traveling wave tube.
Physical Review E, 2004Co-Authors: John G. Wohlbier, John H BooskeAbstract:We present a view of the physics of Phase Distortion in a traveling wave tube (TWT) based on unique insights afforded by the MUSE models of a TWT [J. W\"ohlbier, J. Booske, and I. Dobson, IEEE Trans. Plasma Sci. 30, 1063 (2002)]. The conclusion, supported by analytic theory and simulations, is that prior to gain compression Phase Distortion is due to harmonic frequencies in the electron beam and the resulting ``intermodulation'' frequency at the fundamental, and not the often cited ``slowing down of electrons in the electron beam.'' We draw these conclusions based on MUSE simulations that allow explicit control of electron beam frequency content, an analytic solution to the S-MUSE model [J. W\"ohlbier, J. Booske, and I. Dobson, IEEE Trans. Plasma Sci. 30, 1063 (2002)] that reveals that Phase Distortion is due to the fact that the fundamental frequency is an intermodulation product of itself, and large signal LATTE [J. W\"ohlbier, J. Booske, and I. Dobson, IEEE Trans. Plasma Sci. 30, 1063 (2002)] simulations that are modified to remove the effect of the slowing down of electrons in the electron beam. As applications of the theory we compare S-MUSE simulations to an amplitude Phase model using the analytic Phase transfer curve, we study dependence of Phase Distortion on circuit dispersion and electron beam parameters at the second harmonic with large signal LATTE simulations for narrow and wide band TWT designs, and we consider the Phase Distortion theory in the context of TWT linearization.
-
A new view of Phase Distortion in a traveling wave tube
4th IEEE International Conference on Vacuum Electronics 2003, 1Co-Authors: John G. Wohlbier, John H Booske, Ian DobsonAbstract:The paper deals about the Phase Distortion in a Traveling Wave Tube. It is based on unique insights afforded by the MUSE model of a TWT. The Phase Distortion on dc and harmonic frequencies is studied via MUSE simulations. An approximate analytic solution to the S-MUSE model reveals that Phase Distortion up to the 1 dB gain compression point is due to the fact that the fundamental frequency is an intermodulation product of itself. Simulations are also compared to the large signal code LATTE. The majority of the Phase Distortion prior to gain compression is not due to the average slowing down of electrons was been analysed.
John G. Wohlbier - One of the best experts on this subject based on the ideXlab platform.
-
Phase Distortion mechanisms in linear beam vacuum devices
IEEE Transactions on Plasma Science, 2005Co-Authors: John G. WohlbierAbstract:The mechanism for Phase Distortion in linear beam vacuum devices is identified in the simplest system that pertains to such devices, the force-free drifting electron beam. We show that the dominant cause of Phase Distortion in a force-free drifting beam is the inverse dependence of arrival time on velocity for an electron, i.e., the ``$1/u$ nonlinearity,'' and that a secondary cause of Phase Distortion is the nonlinearity of the velocity modulation. We claim that this is the mechanism for Phase Distortion in all linear beam vacuum devices, and provide evidence from a traveling wave tube calculation. Finally, we discuss the force-free drifting beam example in the context of the "self-intermodulation" description of Phase Distortion recently described in Refs. [J. W\"ohlbier and J. Booske, Phys. Rev. E, vol. 69, 2004, 066502], [J. W\"ohlbier and J. Booske, IEEE Trans. Elec. Devices, To appear.]
-
Mechanisms for Phase Distortion in a traveling wave tube.
Physical review. E Statistical nonlinear and soft matter physics, 2004Co-Authors: John G. Wohlbier, John H BooskeAbstract:We present a view of the physics of Phase Distortion in a traveling wave tube (TWT) based on unique insights afforded by the MUSE models of a TWT [IEEE Trans. Plasma Sci. 30, 1063 (2002)]]. The conclusion, supported by analytic theory and simulations, is that prior to gain compression Phase Distortion is due to harmonic frequencies in the electron beam and the resulting "intermodulation" frequency at the fundamental, and not the often cited "slowing down of electrons in the electron beam." We draw these conclusions based on MUSE simulations that allow explicit control of electron beam frequency content, an analytic solution to the S-MUSE model [IEEE Trans. Plasma Sci. 30, 1063 (2002)]] that reveals that Phase Distortion is due to the fact that the fundamental frequency is an intermodulation product of itself, and large signal LATTE [IEEE Trans. Plasma Sci. 30, 1063 (2002)]] simulations that are modified to remove the effect of the slowing down of electrons in the electron beam. As applications of the theory we compare S-MUSE simulations to an amplitude Phase model using the analytic Phase transfer curve, we study dependence of Phase Distortion on circuit dispersion and electron beam parameters at the second harmonic with large signal LATTE simulations for narrow and wide band TWT designs, and we consider the Phase Distortion theory in the context of TWT linearization.
-
Mechanisms for Phase Distortion in a traveling wave tube.
Physical Review E, 2004Co-Authors: John G. Wohlbier, John H BooskeAbstract:We present a view of the physics of Phase Distortion in a traveling wave tube (TWT) based on unique insights afforded by the MUSE models of a TWT [J. W\"ohlbier, J. Booske, and I. Dobson, IEEE Trans. Plasma Sci. 30, 1063 (2002)]. The conclusion, supported by analytic theory and simulations, is that prior to gain compression Phase Distortion is due to harmonic frequencies in the electron beam and the resulting ``intermodulation'' frequency at the fundamental, and not the often cited ``slowing down of electrons in the electron beam.'' We draw these conclusions based on MUSE simulations that allow explicit control of electron beam frequency content, an analytic solution to the S-MUSE model [J. W\"ohlbier, J. Booske, and I. Dobson, IEEE Trans. Plasma Sci. 30, 1063 (2002)] that reveals that Phase Distortion is due to the fact that the fundamental frequency is an intermodulation product of itself, and large signal LATTE [J. W\"ohlbier, J. Booske, and I. Dobson, IEEE Trans. Plasma Sci. 30, 1063 (2002)] simulations that are modified to remove the effect of the slowing down of electrons in the electron beam. As applications of the theory we compare S-MUSE simulations to an amplitude Phase model using the analytic Phase transfer curve, we study dependence of Phase Distortion on circuit dispersion and electron beam parameters at the second harmonic with large signal LATTE simulations for narrow and wide band TWT designs, and we consider the Phase Distortion theory in the context of TWT linearization.
-
A new view of Phase Distortion in a traveling wave tube
4th IEEE International Conference on Vacuum Electronics 2003, 1Co-Authors: John G. Wohlbier, John H Booske, Ian DobsonAbstract:The paper deals about the Phase Distortion in a Traveling Wave Tube. It is based on unique insights afforded by the MUSE model of a TWT. The Phase Distortion on dc and harmonic frequencies is studied via MUSE simulations. An approximate analytic solution to the S-MUSE model reveals that Phase Distortion up to the 1 dB gain compression point is due to the fact that the fundamental frequency is an intermodulation product of itself. Simulations are also compared to the large signal code LATTE. The majority of the Phase Distortion prior to gain compression is not due to the average slowing down of electrons was been analysed.
Huaixun Zhao - One of the best experts on this subject based on the ideXlab platform.
-
effects of hpa Phase Distortion on system performance
Computer Simulation, 2007Co-Authors: Bo Ai, Taotao Zhang, Zhixing Yang, Yong Wang, Huaixun ZhaoAbstract:There have been few papers discussing about the Phase Distortion of High Power Amplifier (HPA) in detail, and many literatures concerning about the HPA have considered the AM/PM Distortion of Solid State Power Amplifier (SSPA) as zero. The influence of AM/PM Distortion of HPA was deeply analyzed by evaluating BER, Total Degradation (TD) and Power Spectral Density (PSD) performances in wireless OFDM systems. Traveling Wave Tube Amplifier (TWTA) and Solid State Power Amplifier (SSPA) based HPA models are adopted for the computer simulations and analysis. Some useful and important conclusions are drawn to deal with Phase Distortion in the process of HPA preDistortion.
Bo Ai - One of the best experts on this subject based on the ideXlab platform.
-
effects of hpa Phase Distortion on system performance
Computer Simulation, 2007Co-Authors: Bo Ai, Taotao Zhang, Zhixing Yang, Yong Wang, Huaixun ZhaoAbstract:There have been few papers discussing about the Phase Distortion of High Power Amplifier (HPA) in detail, and many literatures concerning about the HPA have considered the AM/PM Distortion of Solid State Power Amplifier (SSPA) as zero. The influence of AM/PM Distortion of HPA was deeply analyzed by evaluating BER, Total Degradation (TD) and Power Spectral Density (PSD) performances in wireless OFDM systems. Traveling Wave Tube Amplifier (TWTA) and Solid State Power Amplifier (SSPA) based HPA models are adopted for the computer simulations and analysis. Some useful and important conclusions are drawn to deal with Phase Distortion in the process of HPA preDistortion.
