The Experts below are selected from a list of 32187 Experts worldwide ranked by ideXlab platform
Thomas J Brazil - One of the best experts on this subject based on the ideXlab platform.
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Nonlinear electrothermal gan hemt model applied to high efficiency power amplifier design
IEEE Transactions on Microwave Theory and Techniques, 2013Co-Authors: Justin B King, Thomas J BrazilAbstract:Gallium Nitride (GaN) high electron-mobility transistors (HEMTs) can operate at very high power-density levels, which may cause a significant temperature rise in the transistor channel. In addition, surface and substrate energy levels, or “traps,” can cause strong dispersion effects from pulsed I-V down to dc timescales. Such effects, for both simulation accuracy and Device reliability purposes, must be accounted for in any Nonlinear Device model. In this paper, a novel Nonlinear high-power GaN HEMT equivalent circuit electrothermal model is described. Features of the model include a Nonlinear thermal subnetwork that is capable of capturing the well-known inherent Nonlinear thermal resistance and capacitance of GaN material. Also included is a comprehensive dispersion model that can be extracted and modeled from simple measurements. The model can very accurately predict the pulsed I -V curves at different pulse widths and duty cycles from isothermal up to the safe-operating area limit. Large-signal one-tone, two-tone, and frequency sweep tests show excellent agreement with measurements. Finally, a continuous class-F amplifier is fabricated, and large-signal frequency sweeps are performed. Comparison between the measured and modeled amplifier metrics demonstrate that the model remains accurate over a 50% bandwidth under real-world conditions.
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a simplified broadband design methodology for linearized high efficiency continuous class f power amplifiers
IEEE Transactions on Microwave Theory and Techniques, 2012Co-Authors: Neal Tuffy, Lei Guan, Thomas J BrazilAbstract:This paper describes the design approach employed for achieving approximated continuous Class-F power amplifier (PA) modes over wide bandwidths. The importance of the Nonlinear Device capacitance for wave-shaping the continuous Class-F voltage and current waveforms is highlighted, thus reducing the Device sensitivity to second and third harmonic impedance terminations. By identifying the high-efficiency regions on the reactance plane for harmonic band placement, the design can be reduced to a fundamental matching problem. The distributed simplified real frequency technique synthesis algorithm can then be utilized to achieve wideband operation. Using a 10-W Cree GaN HEMT Device, greater than 70% efficiency has been measured over a 51% bandwidth from 1.45 to 2.45 GHz, with output powers of 11-16.8 W. The Nonlinear PA was then linearized using digital predistortion with 20-MHz long-term evolution and 40-MHz eight-carrier W-CDMA excitation signals, to attain adjacent channel power ratios below -53 and -49 dBc, respectively. To the best of the authors' knowledge, the measured results represent the best performance obtained from a broadband switch-mode PA, and the best linearized switch-mode performance using 20- and 40-MHz modulated signals.
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a simplified broadband design methodology for linearized high efficiency continuous class f power amplifiers
IEEE Transactions on Microwave Theory and Techniques, 2012Co-Authors: Neal Tuffy, Lei Guan, Anding Zhu, Thomas J BrazilAbstract:This paper describes the design approach employed for achieving approximated continuous Class-F power amplifier (PA) modes over wide bandwidths. The importance of the Nonlinear Device capacitance for wave-shaping the continuous Class-F voltage and current waveforms is highlighted, thus reducing the Device sensitivity to second and third harmonic impedance terminations. By identifying the high-efficiency regions on the reactance plane for harmonic band placement, the design can be reduced to a fundamental matching problem. The distributed simplified real frequency technique synthesis algorithm can then be utilized to achieve wideband operation. Using a 10-W Cree GaN HEMT Device, greater than 70% efficiency has been measured over a 51% bandwidth from 1.45 to 2.45 GHz, with output powers of 11-16.8 W. The Nonlinear PA was then linearized using digital predistortion with 20-MHz long-term evolution and 40-MHz eight-carrier W-CDMA excitation signals, to attain adjacent channel power ratios below -53 and -49 dBc, respectively. To the best of the authors' knowledge, the measured results represent the best performance obtained from a broadband switch-mode PA, and the best linearized switch-mode performance using 20- and 40-MHz modulated signals.
Benjamin S Williams - One of the best experts on this subject based on the ideXlab platform.
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phase locking of a 2 7 thz quantum cascade laser to a microwave reference
Optics Letters, 2009Co-Authors: P Khosropanah, A M Baryshev, Wen Zhang, Willem Jellema, J N Hovenier, J R Gao, T M Klapwijk, D G Paveliev, Benjamin S WilliamsAbstract:We demonstrate the phase locking of a 2.7 THz metal–metal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice Nonlinear Device, of a signal at 182 GHz, which itself is generated by a multiplier chain (x12) from a microwave synthesizer at ~15 GHz. Both laser and reference radiations are coupled into a bolometer mixer, resulting in a beat signal, which is fed into a phase-lock loop. The spectral analysis of the beat signal confirms that the QCL is phase locked. This result opens the possibility to extend heterodyne interferometers into the far-infrared range.
Wen Zhang - One of the best experts on this subject based on the ideXlab platform.
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phase locking of a 2 7 thz quantum cascade laser to a microwave reference
Optics Letters, 2009Co-Authors: P Khosropanah, A M Baryshev, Wen Zhang, Willem Jellema, J N Hovenier, J R Gao, T M Klapwijk, D G Paveliev, Benjamin S WilliamsAbstract:We demonstrate the phase locking of a 2.7 THz metal–metal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice Nonlinear Device, of a signal at 182 GHz, which itself is generated by a multiplier chain (x12) from a microwave synthesizer at ~15 GHz. Both laser and reference radiations are coupled into a bolometer mixer, resulting in a beat signal, which is fed into a phase-lock loop. The spectral analysis of the beat signal confirms that the QCL is phase locked. This result opens the possibility to extend heterodyne interferometers into the far-infrared range.
D A Ritchie - One of the best experts on this subject based on the ideXlab platform.
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phase locking of a 2 7 thz quantum cascade laser to a mode locked erbium doped fibre laser
Nature Photonics, 2010Co-Authors: S Barbieri, Pierre Gellie, G Santarelli, Lu Ding, W Maineult, C Sirtori, R Colombelli, Harvey E Beere, D A RitchieAbstract:We demonstrate phase-locking of a 2.7-THz metalmetal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice Nonlinear Device, of a signal at 182 GHz, which itself is generated by a multiplier-chain (x2x3x2) from a microwave synthesizer at 15 GHz. Both laser and reference radiations are coupled into a hot electron bolometer mixer, resulting in a beat signal, which is fed into a phase-lock loop. Spectral analysis of the beat signal (see fig. 1) confirms that the QCL is phase locked. This result opens the possibility to extend heterodyne interferometers into the far-infrared range.
P Khosropanah - One of the best experts on this subject based on the ideXlab platform.
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phase locking of a 2 7 thz quantum cascade laser to a microwave reference
Optics Letters, 2009Co-Authors: P Khosropanah, A M Baryshev, Wen Zhang, Willem Jellema, J N Hovenier, J R Gao, T M Klapwijk, D G Paveliev, Benjamin S WilliamsAbstract:We demonstrate the phase locking of a 2.7 THz metal–metal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice Nonlinear Device, of a signal at 182 GHz, which itself is generated by a multiplier chain (x12) from a microwave synthesizer at ~15 GHz. Both laser and reference radiations are coupled into a bolometer mixer, resulting in a beat signal, which is fed into a phase-lock loop. The spectral analysis of the beat signal confirms that the QCL is phase locked. This result opens the possibility to extend heterodyne interferometers into the far-infrared range.
