In this paper,high-power LED with many integrated chips is used as thermal resistance analysis research object, and we do thermal resistance testing technology research on it. We put forward the thermocouple point con...In this paper,high-power LED with many integrated chips is used as thermal resistance analysis research object, and we do thermal resistance testing technology research on it. We put forward the thermocouple point contact test method. According to the principle that LED forward voltage changes with temperature,LED heat sink to surface temperature distribution is studied directly in the test,and then we analyze the thermal resistance of high-power LED with many integrated chips when its secondary packaging is introduced. This method makes the measurement of thermal resistance of LED more rapid and convenient. It provides an effective assessment method for the analysis of high power LED device design and engineering application.展开更多
The power and voltage levels of renewable energy resources is growing with the evolution of the power electronics and switching module technologies.For that,the need for the development of a compact and highly efficie...The power and voltage levels of renewable energy resources is growing with the evolution of the power electronics and switching module technologies.For that,the need for the development of a compact and highly efficient solid-state transformer is becoming a critical task in-order to integrate the current AC grid with the new renewable energy systems.The objective of this paper is to present the design,implementation,and testing of a compact multi-port solid-state transformer for microgrid integration applications.The proposed system has a four-port transformer and four converters connected to the ports.The transformer has four windings integrated on a single common core.Thus,it can integrate different renewable energy resources and energy storage systems.Each port has a rated power of 25 kW,and the switching frequency is pushed to 50 k Hz.The ports are chosen to represent a realistic industrial microgrid model consisting of grid,energy storage system,photovoltaic system,and load.The grid port is designed to operate at 4.16 k VAC corresponding to 7.2 kV DC bus voltage,while the other three ports operate at 500 VDC.Moreover,the grid,energy storage and photovoltaic ports are active ports with dual active bridge topologies,while the load port is a passive port with full bridge rectifier one.The proposed design is first validated with simulation results,and then the proposed transformer is implemented and tested.Experimental results show that the designed system is suitable for 4.16 k VAC medium voltage grid integration.展开更多
High power vertical cavity surface emitting lasers(VCSEKLs) with large aperture have been fabricated through improving passivation, lateral oxidation and heat dissipation techniques. Different from conventional three ...High power vertical cavity surface emitting lasers(VCSEKLs) with large aperture have been fabricated through improving passivation, lateral oxidation and heat dissipation techniques. Different from conventional three quantum well structures, a periodic gain active region with nine quantum wells was incorporated into the VCSEL structure, with which high efficiency and high power operation were expected. The nine quantum wells were divided into three groups with each of them located at the antinodes of the cavity to enhance the coupling between the optical field and the gain region. Large aperture and bottom-emitting configuration were used to improve the beam quality and the heat dissipation. A maximum output power of 1.4 W was demonstrated at CW operation for a 400 μm-diameter device. The lasing wavelength shifted to 995.5 nm with a FWHM of 2 nm at a current of 4.8 A due to the internal heating and the absence of active water cooling. A ring-shape far field pattern was induced by the non-homogeneous lateral current distribution in large diameter device. The light intensity at the center of the ring increased with increasing current. A symmetric round light spot at the center and single transverse mode operation with a divergence angle of 16° were observed with current beyond 4.8 A.展开更多
Catastrophic degradation of high power laser diodes is due to the generation of extended defects inside the active parts of the laser structure during the laser operation.The mechanism driving the degradation is stron...Catastrophic degradation of high power laser diodes is due to the generation of extended defects inside the active parts of the laser structure during the laser operation.The mechanism driving the degradation is strongly related to the existence of localized thermal stresses generated during the laser operation.These thermal stresses can overcome the yield strength of the materials forming the active part of the laser diode.Different factors contribute to reduce the laser power threshold for degradation.Among them the thermal transport across the laser structure constitutes a critical issue for the reliability of the device.展开更多
The semiconductor laser array with single-mode emission is presented in this paper.The 6-μm-wide ridge waveguides(RWGs)are fabricated to select the lateral mode.Thus the fundamental mode of laser array can be obtaine...The semiconductor laser array with single-mode emission is presented in this paper.The 6-μm-wide ridge waveguides(RWGs)are fabricated to select the lateral mode.Thus the fundamental mode of laser array can be obtained by the RWGs.And the maximum output power of single-mode emission can reach 36 W at an injection current of 43 A,after that,a kink will appear.The slow axis(SA)far-field divergence angle of the unit is 13.65.The beam quality factor M;of the units determined by the second-order moment(SOM)method,is 1.2.This single-mode emission laser array can be used for laser processing.展开更多
Objective The hippocampus is thought to be a vulnerable target of microwave exposure.The aim of the present study was to investigate whether 20-hydroxyecdysone(20E)acted as a fate regulator of adult rat hippocampal ne...Objective The hippocampus is thought to be a vulnerable target of microwave exposure.The aim of the present study was to investigate whether 20-hydroxyecdysone(20E)acted as a fate regulator of adult rat hippocampal neural stem cells(NSCs).Furthermore,we investigated if 20E attenuated high power microwave(HMP)radiation-induced learning and memory deficits.Methods Sixty male Sprague-Dawley rats were randomly divided into three groups:normal controls,radiation treated,and radiation+20E treated.Rats in the radiation and radiation+20E treatment groups were exposed to HPM radiation from a microwave emission system.The learning and memory abilities of the rats were assessed using the Morris water maze test.Primary adult rat hippocampal NSCs were isolated in vitro and cultured to evaluate their proliferation and differentiation.In addition,hematoxylin&eosin staining,western blotting,and immunofluorescence were used to detect changes in the rat brain and the proliferation and differentiation of the adult rat hippocampal NSCs after HPM radiation exposure.Results The results showed that 20E induced neuronal differentiation of adult hippocampal NSCs from HPM radiation-exposed rats via the Wnt3a/β-catenin signaling pathway in vitro.Furthermore,20E facilitated neurogenesis in the subgranular zone of the rat brain following HPM radiation exposure.Administration of 20E attenuated learning and memory deficits in HPM radiation-exposed rats and frizzled-related protein(FRZB)reduced the 20E-induced nuclear translocation ofβ-catenin,while FRZB treatment also reversed 20E-induced neuronal differentiation of NSCs in vitro.Conclusion These results suggested that 20E was a fate regulator of adult rat hippocampal NSCs,where it played a role in attenuating HPM radiation-induced learning and memory deficits.展开更多
An atomic-level controlled etching(ACE)technology is invstigated for the fabrication of recessed gate AlGaN/GaN high-electron-mobility transistors(HEMTs)with high power added efficiency.We compare the recessed gate HE...An atomic-level controlled etching(ACE)technology is invstigated for the fabrication of recessed gate AlGaN/GaN high-electron-mobility transistors(HEMTs)with high power added efficiency.We compare the recessed gate HEMTs with conventional etching(CE)based chlorine,Cl_(2)-only ACE and BCl^(3)/Cl_(2)ACE,respectively.The mixed radicals of BCl_(3)/Cl_(2)were used as the active reactants in the step of chemical modification.For ensuring precise and controllable etching depth and low etching damage,the kinetic energy of argon ions was accurately controlled.These argon ions were used precisely to remove the chemical modified surface atomic layer.Compared to the HEMTs with CE,the characteristics of devices fabricated by ACE are significantly improved,which benefits from significant reduction of etching damage.For BCl_(3)/Cl_(2)ACE recessed HEMTs,the load pull test at 17 GHz shows a high power added efficiency(PAE)of 59.8%with an output power density of 1.6 W/mm at Vd=10 V,and a peak PAE of 44.8%with an output power density of 3.2 W/mm at Vd=20 V in a continuous-wave mode.展开更多
We report on a research of the loading of ultracold sodium atoms in an optical dipole trap,generated by two beams from a high power fiber laser.The effects of optical trap light power on atomic number,temperature and ...We report on a research of the loading of ultracold sodium atoms in an optical dipole trap,generated by two beams from a high power fiber laser.The effects of optical trap light power on atomic number,temperature and phase space density are experimentally investigated.A simple theory is proposed and it is in good accordance with the experimental results of the loaded atomic numbers.In a general estimation,an optimal value for each beam with a power of 9 W from the fiber laser is achieved.Our results provide a further understanding of the loading process of optical dipole trap and laid the foundation for generation of a sodium Bose–Einstein condensation with an optical dipole trap.展开更多
This paper presents the concept of a Dielectric-lined Multiwave Cerenkov Generator producing high power millimeter waves, which has been investigated with a two and onehalf dimensional electromagnetic relativistic Par...This paper presents the concept of a Dielectric-lined Multiwave Cerenkov Generator producing high power millimeter waves, which has been investigated with a two and onehalf dimensional electromagnetic relativistic Particle-in-Cell (PIC) plasma simulation code. Themodified device can operate in a lower diode-voltage regime with much higher radiation efficiencyand slight downshift of operation frequency. There exist the optima for the permittivity of thedielectric liner and for the magnitude of the guiding magnetic field. The required intensity of theguiding field is reduced by the introduction of the liner. The enhanced propagation of the electronbeam is studied in the presence of the liner.展开更多
This paper proposed the high-frequency, multi-harmonic-controlled, Class-F power amplifier (PA) implemented with 0.5 μm GaN Hetrojunction Electron Mobility Transistor (HEMT). For PA design at high frequencies, parasi...This paper proposed the high-frequency, multi-harmonic-controlled, Class-F power amplifier (PA) implemented with 0.5 μm GaN Hetrojunction Electron Mobility Transistor (HEMT). For PA design at high frequencies, parasitics of a transistor significantly increase the difficulty of harmonic manipulation, compared to low-frequency cases. To overcome this issue, we propose a novel design methodology based on a band-reject, low-pass, output matching network, which is realized with passive components. This network provides optimal fundamental impedance and allows harmonic control up to the third order to enable an efficient Class-F behavior. The implemented PA exhibits performance at 2.5 GHz with a 50% PAE, 14 dB gain, and 10 W output power.展开更多
In medium voltage high power applications,multi-level current source converters(CSCs)are good candidate to increase system power region,reliability,and the quality of output waveforms.Compared with widely researched v...In medium voltage high power applications,multi-level current source converters(CSCs)are good candidate to increase system power region,reliability,and the quality of output waveforms.Compared with widely researched voltage source multi-level converters(MLCs),the current source MLCs have the advantages of inherent short-circuit protection,high power capability and high quality of output current waveforms.The main features of MLCs include reduced harmonics,lower switching frequency and reduced current stress on each device which is a particularly important for high power application with low voltage and high current requirements.This paper conducts a general review of the current research about MLCs in higher power medium voltage application.The different types of parallel structure based MLCs and the modulation methodologies will be introduced and compared.Specifically,the circuit analysis of the common-mode(CM)loop for parallel structures will be conducted,the common-mode voltage(CMV)and circulating current suppression methods developed on the base of multilevel modulations will be addressed.展开更多
The high power microwave(HPM) damage effect on the Al Ga As/In Ga As pseudomorphic high electron mobility transistor(p HEMT) is studied by simulation and experiments. Simulated results suggest that the HPM damage to p...The high power microwave(HPM) damage effect on the Al Ga As/In Ga As pseudomorphic high electron mobility transistor(p HEMT) is studied by simulation and experiments. Simulated results suggest that the HPM damage to p HEMT is due to device burn-out caused by the emerging current path and strong electric field beneath the gate. Besides, the results demonstrate that the damage power threshold decreases but the energy threshold slightly increases with the increase of pulse-width, indicating that HPM with longer pulse-width requires lower power density but more energy to cause the damage to p HEMT. The empirical formulas are proposed to describe the pulse-width dependence. Then the experimental data validate the pulse-width dependence and verify that the proposed formula P = 55τ-0.06 is capable of quickly and accurately estimating the HPM damage susceptibility of p HEMT. Finally the interior observation of damaged samples by scanning electron microscopy(SEM) illustrates that the failure mechanism of the HPM damage to p HEMT is indeed device burn-out and the location beneath the gate near the source side is most susceptible to burn-out, which is in accordance with the simulated results.展开更多
In this paper, we present the damage effect and mechanism of high power microwave(HPM) on Al GaAs/GaAs pseudomorphic high-electron-mobility transistor(p HEMT) of low-noise amplifier(LNA). A detailed investigation is c...In this paper, we present the damage effect and mechanism of high power microwave(HPM) on Al GaAs/GaAs pseudomorphic high-electron-mobility transistor(p HEMT) of low-noise amplifier(LNA). A detailed investigation is carried out by simulation and experiment study. A two-dimensional electro-thermal model of the typical GaAs p HEMT induced by HPM is established in this paper. The simulation result reveals that avalanche breakdown, intrinsic excitation, and thermal breakdown all contribute to damage process. Heat accumulation occurs during the positive half cycle and the cylinder under the gate near the source side is most susceptible to burn-out. Experiment is carried out by injecting high power microwave into GaAs p HEMT LNA samples. It is found that the damage to LNA is because of the burn-out at first stage p HEMT. The interiors of the damaged samples are observed by scanning electron microscopy(SEM) and energy dispersive spectrometer(EDS). Experimental results accord well with the simulation of our model.展开更多
In order to test the klystrons operated at a frequency of 3.7 GHz in a continuouswave(CW)mode,a type of water load to absorb its power up to 750 kW is presented.Thedistilled water sealed with an RF ceramic window is u...In order to test the klystrons operated at a frequency of 3.7 GHz in a continuouswave(CW)mode,a type of water load to absorb its power up to 750 kW is presented.Thedistilled water sealed with an RF ceramic window is used as the absorbent.At a frequency rangeof 70 MHz,the VSWR(Voltage Standing Wave Ratio)is below 1.2,and the rise in temperatureof water is about 30℃ at the highest power level.展开更多
The CrN and Cr-Al-Si-N films were deposited on Si wafer and SUS 304 substrates by a hybrid coating system with high power impulse magnetron sputtering (HIPIMS) and a DC pulse sputtering using Cr and AlSi targets under...The CrN and Cr-Al-Si-N films were deposited on Si wafer and SUS 304 substrates by a hybrid coating system with high power impulse magnetron sputtering (HIPIMS) and a DC pulse sputtering using Cr and AlSi targets under N2/Ar atmosphere.By varying the sputtering current of the AlSi target in the range of 0-2.5 A,both the Al and Si contents in the films increased gradually from 0 to 19.1% and 11.1% (mole fraction),respectively.The influences of the AlSi cathode DC pulse current on the microstructure,phase constituents,mechanical properties,and oxidation behaviors of the Cr-Al-Si-N films were investigated systematically.The results indicate that the as-deposited Cr-Al-Si-N films possess the typical nanocomposite structure,namely the face centered cubic (Cr,Al)N nano-crystallites are embedded in the amorphous Si3N4 matrix.With increasing the Al and Si contents,the hardness of the film first increases from 20.8 GPa for the CrN film to the peak value of 29.4 GPa for the Cr0.23Al0.14Si0.07 N film,and then decreases gradually.In the meanwhile,the Cr0.23Al0.14Si0.07N film also possesses excellent high-temperature oxidation resistance that is much better than that of the CrN film at 900 or 1000 °C.展开更多
We observe the phenomenon of priority oscillation of the unexpected σ -polarization in high-power Nd:YVO 4 ring laser. The severe thermal lens of the σ -polarized lasing, compared with the π-polarized lasing, is th...We observe the phenomenon of priority oscillation of the unexpected σ -polarization in high-power Nd:YVO 4 ring laser. The severe thermal lens of the σ -polarized lasing, compared with the π-polarized lasing, is the only reason for the phenomenon. By designing a wedge Nd:YVO 4 crystal as the gain medium, the unexpected σ -polarization is completely suppressed in the entire range of pump powers, and the polarization stability of the expected π-polarized output is enhanced. With the output power increasing from threshold to the maximum power, no σ -polarization lasing is observed. As a result, 25.3 W of stable single-frequency laser output at 532 nm is experimentally demonstrated.展开更多
Proposed and demonstrated is a novel computer modeling method for high power light emitting diodes(LEDs). It contains geometrical structure and optical property of high power LED as well as LED dies definition with it...Proposed and demonstrated is a novel computer modeling method for high power light emitting diodes(LEDs). It contains geometrical structure and optical property of high power LED as well as LED dies definition with its spatial and angular distribution. Merits and non-merits of traditional modeling methods when applied to high power LEDs based on secondary optical design are discussed. Two commercial high power LEDs are simulated using the proposed computer modeling method. Correlation coefficient is proposed to compare and analyze the simulation results and manufacturing specifications. The source model is precisely demonstrated by obtaining above 99% in correlation coefficient with different surface incident angle intervals.展开更多
The experimental study of ultra-wideband (UWB) technology, its generation and on-line measurement are presented. An experimental repetitive UWB system is designed, manufactured, and tested. High-pressure spark gap swi...The experimental study of ultra-wideband (UWB) technology, its generation and on-line measurement are presented. An experimental repetitive UWB system is designed, manufactured, and tested. High-pressure spark gap switch and its components, as well as oil spark gap switch are studied experimentally on the system. Experimental results indicate that the system operates at a 200 pps repetitive rate with a stable performance. 100 MW peak power UWB pulses are obtained on the system. Fast-time response capacitive divider is designed and fabricated, allowing for an accurate measurement of the high power UWB signal. The main issues related to the design of the switch and the UWB signal online measurement are discussed.展开更多
基金Sponsored by the Heilongjiang Provincial Project(Grant No.12511121)the Harbin City Innovation Talent Project(Grant No.2011RFXXG019)the National Science and Technology Support Project(Grant No.2012BAH28F02)
文摘In this paper,high-power LED with many integrated chips is used as thermal resistance analysis research object, and we do thermal resistance testing technology research on it. We put forward the thermocouple point contact test method. According to the principle that LED forward voltage changes with temperature,LED heat sink to surface temperature distribution is studied directly in the test,and then we analyze the thermal resistance of high-power LED with many integrated chips when its secondary packaging is introduced. This method makes the measurement of thermal resistance of LED more rapid and convenient. It provides an effective assessment method for the analysis of high power LED device design and engineering application.
基金supported by the National Science Foundation under Grant No.1650470,GRAPES I/UCRC program。
文摘The power and voltage levels of renewable energy resources is growing with the evolution of the power electronics and switching module technologies.For that,the need for the development of a compact and highly efficient solid-state transformer is becoming a critical task in-order to integrate the current AC grid with the new renewable energy systems.The objective of this paper is to present the design,implementation,and testing of a compact multi-port solid-state transformer for microgrid integration applications.The proposed system has a four-port transformer and four converters connected to the ports.The transformer has four windings integrated on a single common core.Thus,it can integrate different renewable energy resources and energy storage systems.Each port has a rated power of 25 kW,and the switching frequency is pushed to 50 k Hz.The ports are chosen to represent a realistic industrial microgrid model consisting of grid,energy storage system,photovoltaic system,and load.The grid port is designed to operate at 4.16 k VAC corresponding to 7.2 kV DC bus voltage,while the other three ports operate at 500 VDC.Moreover,the grid,energy storage and photovoltaic ports are active ports with dual active bridge topologies,while the load port is a passive port with full bridge rectifier one.The proposed design is first validated with simulation results,and then the proposed transformer is implemented and tested.Experimental results show that the designed system is suitable for 4.16 k VAC medium voltage grid integration.
文摘High power vertical cavity surface emitting lasers(VCSEKLs) with large aperture have been fabricated through improving passivation, lateral oxidation and heat dissipation techniques. Different from conventional three quantum well structures, a periodic gain active region with nine quantum wells was incorporated into the VCSEL structure, with which high efficiency and high power operation were expected. The nine quantum wells were divided into three groups with each of them located at the antinodes of the cavity to enhance the coupling between the optical field and the gain region. Large aperture and bottom-emitting configuration were used to improve the beam quality and the heat dissipation. A maximum output power of 1.4 W was demonstrated at CW operation for a 400 μm-diameter device. The lasing wavelength shifted to 995.5 nm with a FWHM of 2 nm at a current of 4.8 A due to the internal heating and the absence of active water cooling. A ring-shape far field pattern was induced by the non-homogeneous lateral current distribution in large diameter device. The light intensity at the center of the ring increased with increasing current. A symmetric round light spot at the center and single transverse mode operation with a divergence angle of 16° were observed with current beyond 4.8 A.
基金funded by the Spanish Government(MAT-2010-20441-C02)
文摘Catastrophic degradation of high power laser diodes is due to the generation of extended defects inside the active parts of the laser structure during the laser operation.The mechanism driving the degradation is strongly related to the existence of localized thermal stresses generated during the laser operation.These thermal stresses can overcome the yield strength of the materials forming the active part of the laser diode.Different factors contribute to reduce the laser power threshold for degradation.Among them the thermal transport across the laser structure constitutes a critical issue for the reliability of the device.
基金Project supported by the National Science and Technology Major Project of China(Grant Nos.2018YFB0504600and 2017YFB0405102)the Frontier Science Key Program of the President of the Chinese Academy of Sciences(Grant No.QYZDY-SSW-JSC006)+7 种基金the Pilot Project of the Chinese Academy of Sciences(Grant No.XDB43030302)the National Natural Science Foundation of China(Grant Nos.62090051,62090052,62090054,11874353,61935009,61934003,61904179,61727822,61805236,62004194,and 61991433)the Science and Technology Development Project of Jilin Province,China(Grant Nos.20200401062GX,202001069GX,20200501006GX,20200501007GX,20200501008GX,and 20190302042GX)the Key Research and Development Project of Guangdong Province,China(Grant No.2020B090922003)the Equipment Pre-researchChina(Grant No.2006ZYGG0304)the Special Scientific Research Project of the Academician Innovation Platform in Hainan Province,China(Grant No.YSPTZX202034)the Dawn Talent Training Program of CIOMP,China。
文摘The semiconductor laser array with single-mode emission is presented in this paper.The 6-μm-wide ridge waveguides(RWGs)are fabricated to select the lateral mode.Thus the fundamental mode of laser array can be obtained by the RWGs.And the maximum output power of single-mode emission can reach 36 W at an injection current of 43 A,after that,a kink will appear.The slow axis(SA)far-field divergence angle of the unit is 13.65.The beam quality factor M;of the units determined by the second-order moment(SOM)method,is 1.2.This single-mode emission laser array can be used for laser processing.
基金supported by grants from the National Natural Science Fund[NO.2015AA8092018A]the Natural Science Foundation of Chongqing municipality[NO.cstc2018jcyjAX0186]
文摘Objective The hippocampus is thought to be a vulnerable target of microwave exposure.The aim of the present study was to investigate whether 20-hydroxyecdysone(20E)acted as a fate regulator of adult rat hippocampal neural stem cells(NSCs).Furthermore,we investigated if 20E attenuated high power microwave(HMP)radiation-induced learning and memory deficits.Methods Sixty male Sprague-Dawley rats were randomly divided into three groups:normal controls,radiation treated,and radiation+20E treated.Rats in the radiation and radiation+20E treatment groups were exposed to HPM radiation from a microwave emission system.The learning and memory abilities of the rats were assessed using the Morris water maze test.Primary adult rat hippocampal NSCs were isolated in vitro and cultured to evaluate their proliferation and differentiation.In addition,hematoxylin&eosin staining,western blotting,and immunofluorescence were used to detect changes in the rat brain and the proliferation and differentiation of the adult rat hippocampal NSCs after HPM radiation exposure.Results The results showed that 20E induced neuronal differentiation of adult hippocampal NSCs from HPM radiation-exposed rats via the Wnt3a/β-catenin signaling pathway in vitro.Furthermore,20E facilitated neurogenesis in the subgranular zone of the rat brain following HPM radiation exposure.Administration of 20E attenuated learning and memory deficits in HPM radiation-exposed rats and frizzled-related protein(FRZB)reduced the 20E-induced nuclear translocation ofβ-catenin,while FRZB treatment also reversed 20E-induced neuronal differentiation of NSCs in vitro.Conclusion These results suggested that 20E was a fate regulator of adult rat hippocampal NSCs,where it played a role in attenuating HPM radiation-induced learning and memory deficits.
基金supported by the National Natural Science Foundation of China(Grant Nos.62090014,62188102,62104184,62104178,and 62104179)the Fundamental Research Funds for the Central Universities of China(Grant Nos.XJS201102,XJS211101,XJS211106,and ZDRC2002)。
文摘An atomic-level controlled etching(ACE)technology is invstigated for the fabrication of recessed gate AlGaN/GaN high-electron-mobility transistors(HEMTs)with high power added efficiency.We compare the recessed gate HEMTs with conventional etching(CE)based chlorine,Cl_(2)-only ACE and BCl^(3)/Cl_(2)ACE,respectively.The mixed radicals of BCl_(3)/Cl_(2)were used as the active reactants in the step of chemical modification.For ensuring precise and controllable etching depth and low etching damage,the kinetic energy of argon ions was accurately controlled.These argon ions were used precisely to remove the chemical modified surface atomic layer.Compared to the HEMTs with CE,the characteristics of devices fabricated by ACE are significantly improved,which benefits from significant reduction of etching damage.For BCl_(3)/Cl_(2)ACE recessed HEMTs,the load pull test at 17 GHz shows a high power added efficiency(PAE)of 59.8%with an output power density of 1.6 W/mm at Vd=10 V,and a peak PAE of 44.8%with an output power density of 3.2 W/mm at Vd=20 V in a continuous-wave mode.
基金Project supported by the National Key R&D Program of China(Grant No.2017YFA0304203)the National Natural Science Foundation of China(Grant Nos.61722507,61675121,61705123,62020106014,and 62011530047)+4 种基金the PCSIRT(Grant No.IRT-17R70)the 111 Project(Grant No.D18001)the Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi(OIT)the Applied Basic Research Project of Shanxi Province,China(Grant Nos.201801D221004,201901D211191,and 201901D211188)the Shanxi 1331 KSC.
文摘We report on a research of the loading of ultracold sodium atoms in an optical dipole trap,generated by two beams from a high power fiber laser.The effects of optical trap light power on atomic number,temperature and phase space density are experimentally investigated.A simple theory is proposed and it is in good accordance with the experimental results of the loaded atomic numbers.In a general estimation,an optimal value for each beam with a power of 9 W from the fiber laser is achieved.Our results provide a further understanding of the loading process of optical dipole trap and laid the foundation for generation of a sodium Bose–Einstein condensation with an optical dipole trap.
文摘This paper presents the concept of a Dielectric-lined Multiwave Cerenkov Generator producing high power millimeter waves, which has been investigated with a two and onehalf dimensional electromagnetic relativistic Particle-in-Cell (PIC) plasma simulation code. Themodified device can operate in a lower diode-voltage regime with much higher radiation efficiencyand slight downshift of operation frequency. There exist the optima for the permittivity of thedielectric liner and for the magnitude of the guiding magnetic field. The required intensity of theguiding field is reduced by the introduction of the liner. The enhanced propagation of the electronbeam is studied in the presence of the liner.
文摘This paper proposed the high-frequency, multi-harmonic-controlled, Class-F power amplifier (PA) implemented with 0.5 μm GaN Hetrojunction Electron Mobility Transistor (HEMT). For PA design at high frequencies, parasitics of a transistor significantly increase the difficulty of harmonic manipulation, compared to low-frequency cases. To overcome this issue, we propose a novel design methodology based on a band-reject, low-pass, output matching network, which is realized with passive components. This network provides optimal fundamental impedance and allows harmonic control up to the third order to enable an efficient Class-F behavior. The implemented PA exhibits performance at 2.5 GHz with a 50% PAE, 14 dB gain, and 10 W output power.
文摘In medium voltage high power applications,multi-level current source converters(CSCs)are good candidate to increase system power region,reliability,and the quality of output waveforms.Compared with widely researched voltage source multi-level converters(MLCs),the current source MLCs have the advantages of inherent short-circuit protection,high power capability and high quality of output current waveforms.The main features of MLCs include reduced harmonics,lower switching frequency and reduced current stress on each device which is a particularly important for high power application with low voltage and high current requirements.This paper conducts a general review of the current research about MLCs in higher power medium voltage application.The different types of parallel structure based MLCs and the modulation methodologies will be introduced and compared.Specifically,the circuit analysis of the common-mode(CM)loop for parallel structures will be conducted,the common-mode voltage(CMV)and circulating current suppression methods developed on the base of multilevel modulations will be addressed.
基金Project supported by the National Basic Research Program of China(Grant No.2014CB339900)the National Natural Science Foundation of China(Grant No.60776034)
文摘The high power microwave(HPM) damage effect on the Al Ga As/In Ga As pseudomorphic high electron mobility transistor(p HEMT) is studied by simulation and experiments. Simulated results suggest that the HPM damage to p HEMT is due to device burn-out caused by the emerging current path and strong electric field beneath the gate. Besides, the results demonstrate that the damage power threshold decreases but the energy threshold slightly increases with the increase of pulse-width, indicating that HPM with longer pulse-width requires lower power density but more energy to cause the damage to p HEMT. The empirical formulas are proposed to describe the pulse-width dependence. Then the experimental data validate the pulse-width dependence and verify that the proposed formula P = 55τ-0.06 is capable of quickly and accurately estimating the HPM damage susceptibility of p HEMT. Finally the interior observation of damaged samples by scanning electron microscopy(SEM) illustrates that the failure mechanism of the HPM damage to p HEMT is indeed device burn-out and the location beneath the gate near the source side is most susceptible to burn-out, which is in accordance with the simulated results.
基金supported by the National Basic Research Program of China(Grant No.2014CB339900)the Open Fund of Key Laboratory of Complex Electromagnetic Environment Science and TechnologyChina Academy of Engineering Physics(Grant No.2015-0214.XY.K)
文摘In this paper, we present the damage effect and mechanism of high power microwave(HPM) on Al GaAs/GaAs pseudomorphic high-electron-mobility transistor(p HEMT) of low-noise amplifier(LNA). A detailed investigation is carried out by simulation and experiment study. A two-dimensional electro-thermal model of the typical GaAs p HEMT induced by HPM is established in this paper. The simulation result reveals that avalanche breakdown, intrinsic excitation, and thermal breakdown all contribute to damage process. Heat accumulation occurs during the positive half cycle and the cylinder under the gate near the source side is most susceptible to burn-out. Experiment is carried out by injecting high power microwave into GaAs p HEMT LNA samples. It is found that the damage to LNA is because of the burn-out at first stage p HEMT. The interiors of the damaged samples are observed by scanning electron microscopy(SEM) and energy dispersive spectrometer(EDS). Experimental results accord well with the simulation of our model.
文摘In order to test the klystrons operated at a frequency of 3.7 GHz in a continuouswave(CW)mode,a type of water load to absorb its power up to 750 kW is presented.Thedistilled water sealed with an RF ceramic window is used as the absorbent.At a frequency rangeof 70 MHz,the VSWR(Voltage Standing Wave Ratio)is below 1.2,and the rise in temperatureof water is about 30℃ at the highest power level.
基金supported by a 2-Year Research Grant of Pusan National University,Korea
文摘The CrN and Cr-Al-Si-N films were deposited on Si wafer and SUS 304 substrates by a hybrid coating system with high power impulse magnetron sputtering (HIPIMS) and a DC pulse sputtering using Cr and AlSi targets under N2/Ar atmosphere.By varying the sputtering current of the AlSi target in the range of 0-2.5 A,both the Al and Si contents in the films increased gradually from 0 to 19.1% and 11.1% (mole fraction),respectively.The influences of the AlSi cathode DC pulse current on the microstructure,phase constituents,mechanical properties,and oxidation behaviors of the Cr-Al-Si-N films were investigated systematically.The results indicate that the as-deposited Cr-Al-Si-N films possess the typical nanocomposite structure,namely the face centered cubic (Cr,Al)N nano-crystallites are embedded in the amorphous Si3N4 matrix.With increasing the Al and Si contents,the hardness of the film first increases from 20.8 GPa for the CrN film to the peak value of 29.4 GPa for the Cr0.23Al0.14Si0.07 N film,and then decreases gradually.In the meanwhile,the Cr0.23Al0.14Si0.07N film also possesses excellent high-temperature oxidation resistance that is much better than that of the CrN film at 900 or 1000 °C.
基金supported by the National High Technology Research and Development Program of China(Grant No.2011AA030203)the National Basic Research Program of China(Grant No.2010CB923101)+1 种基金the National Natural Science Foundation of China(Grant No.61008001)the Natural Science Foundation of Shanxi Province,China(Grant No.2011021003-2)
文摘We observe the phenomenon of priority oscillation of the unexpected σ -polarization in high-power Nd:YVO 4 ring laser. The severe thermal lens of the σ -polarized lasing, compared with the π-polarized lasing, is the only reason for the phenomenon. By designing a wedge Nd:YVO 4 crystal as the gain medium, the unexpected σ -polarization is completely suppressed in the entire range of pump powers, and the polarization stability of the expected π-polarized output is enhanced. With the output power increasing from threshold to the maximum power, no σ -polarization lasing is observed. As a result, 25.3 W of stable single-frequency laser output at 532 nm is experimentally demonstrated.
基金The"863"Project of National Ministry of Science and Technology(2006AA03A175)
文摘Proposed and demonstrated is a novel computer modeling method for high power light emitting diodes(LEDs). It contains geometrical structure and optical property of high power LED as well as LED dies definition with its spatial and angular distribution. Merits and non-merits of traditional modeling methods when applied to high power LEDs based on secondary optical design are discussed. Two commercial high power LEDs are simulated using the proposed computer modeling method. Correlation coefficient is proposed to compare and analyze the simulation results and manufacturing specifications. The source model is precisely demonstrated by obtaining above 99% in correlation coefficient with different surface incident angle intervals.
文摘The experimental study of ultra-wideband (UWB) technology, its generation and on-line measurement are presented. An experimental repetitive UWB system is designed, manufactured, and tested. High-pressure spark gap switch and its components, as well as oil spark gap switch are studied experimentally on the system. Experimental results indicate that the system operates at a 200 pps repetitive rate with a stable performance. 100 MW peak power UWB pulses are obtained on the system. Fast-time response capacitive divider is designed and fabricated, allowing for an accurate measurement of the high power UWB signal. The main issues related to the design of the switch and the UWB signal online measurement are discussed.
