The source area of the Yellow River is located in the northeastern Tibetan Plateau, and is a high-elevation region with the annual mean temperature of-3.9℃. The ice-wedge pseudomorphs discovered in this region are re...The source area of the Yellow River is located in the northeastern Tibetan Plateau, and is a high-elevation region with the annual mean temperature of-3.9℃. The ice-wedge pseudomorphs discovered in this region are recognized as two types.One was found in sandy gravel beds of the second terrace of the Yellow River. This ice-wedge pseudomorph is characterized by higher ratio of breadth/depth, and are 1～1.4 m wide and about 1 m deep. The bottom border of the ice-wedge pseudomorph is round arc in section. Another discovered in the pedestal of the second terrace has lower ratio of width/depth, and is 0.3～1.0 m wide and 1～2 m deep. Its bottom border is sharp. Based on the TL dating, the former was formed at the middle Holocene (5.69±0.43 ka BP and 5.43±0.41 ka BP),that is, the Megathermal, and the latter was formed at the late Last Glacial Maximum (13.49± 1.43 ka BP).Additionally, the thawing-freezing folders discovered in the late Late Pleistocene proluvium are 39.83±3.84 ka BP in age. The study on the ice-wedge pseudomorphs showed that the air temperature was lowered by up to 6～7 ℃ in the source area of the Yellow River when the ice-wedge pseudomorphs and thawing-freezing folds developed.展开更多
The damage effect characteristics of GaAs pseudomorphic high electron mobility transistor(pHEMT)under the irradiation of C band high-power microwave(HPM)is investigated in this paper.Based on the theoretical analysis,...The damage effect characteristics of GaAs pseudomorphic high electron mobility transistor(pHEMT)under the irradiation of C band high-power microwave(HPM)is investigated in this paper.Based on the theoretical analysis,the thermoelectric coupling model is established,and the key damage parameters of the device under typical pulse conditions are predicted,including the damage location,damage power,etc.By the injection effect test and device microanatomy analysis through using scanning electron microscope(SEM)and energy dispersive spectrometer(EDS),it is concluded that the gate metal in the first stage of the device is the vulnerable to HPM damage,especially the side below the gate near the source.The damage power in the injection test is about 40 dBm and in good agreement with the simulation result.This work has a certain reference value for microwave damage assessment of pHEMT.展开更多
文章基于赝高电子迁移率晶体管(Pseudomorphic High Electron Mobility Transistor,PHEMT)工艺,设计一款Ka波段单刀四掷反射式开关芯片。为降低芯片插入损耗和提高隔离度,电路选取并联型反射式拓扑结构。同时,为提高工作带宽和减小芯片...文章基于赝高电子迁移率晶体管(Pseudomorphic High Electron Mobility Transistor,PHEMT)工艺,设计一款Ka波段单刀四掷反射式开关芯片。为降低芯片插入损耗和提高隔离度,电路选取并联型反射式拓扑结构。同时,为提高工作带宽和减小芯片面积,采用高低阻抗变换线替代50Ω传输线方式匹配阻抗。芯片采用0 V和-5 V电压控制支路开关的导通或关断。芯片尺寸为1.85 mm×1.55 mm。实测结果表明,在28~42 GHz工作频带范围内,输入输出回波损耗小于-10 dB,插入损耗小于3.2 dB,隔离度大于38 dB,实现了开关芯片低插损、高隔离度的优异性能。展开更多
基于GaAs PHEMT工艺,设计制作了6-18 GHz驱动放大器单片电路。电路采用三级放大器拓扑结构,＋5 V单电源供电。第一级采用负反馈电路结构,级间采用有耗匹配结构实现工作带宽。为了实现较高的工作效率,对输出级器件进行了负载牵引仿真,确...基于GaAs PHEMT工艺,设计制作了6-18 GHz驱动放大器单片电路。电路采用三级放大器拓扑结构,＋5 V单电源供电。第一级采用负反馈电路结构,级间采用有耗匹配结构实现工作带宽。为了实现较高的工作效率,对输出级器件进行了负载牵引仿真,确定了输出级器件的静态工作点和匹配结构。测试结果表明,在6-18 GHz,增益大于18 d B,输入输出回波损耗小于-10 d B,1 d B压缩点功率输出功率大于21 d Bm,饱和功率大于24 d Bm,功率附加效率大于25%,芯片尺寸为1.35 mm×1.00 mm。该电路具有频带宽、效率高、尺寸小等特点,可用于多种小型封装产品,具有广泛的应用前景。展开更多
基金the Ministry of Land and Resource of P.R.China the National Natural Science Foundation of China(No.40172062).
文摘The source area of the Yellow River is located in the northeastern Tibetan Plateau, and is a high-elevation region with the annual mean temperature of-3.9℃. The ice-wedge pseudomorphs discovered in this region are recognized as two types.One was found in sandy gravel beds of the second terrace of the Yellow River. This ice-wedge pseudomorph is characterized by higher ratio of breadth/depth, and are 1～1.4 m wide and about 1 m deep. The bottom border of the ice-wedge pseudomorph is round arc in section. Another discovered in the pedestal of the second terrace has lower ratio of width/depth, and is 0.3～1.0 m wide and 1～2 m deep. Its bottom border is sharp. Based on the TL dating, the former was formed at the middle Holocene (5.69±0.43 ka BP and 5.43±0.41 ka BP),that is, the Megathermal, and the latter was formed at the late Last Glacial Maximum (13.49± 1.43 ka BP).Additionally, the thawing-freezing folders discovered in the late Late Pleistocene proluvium are 39.83±3.84 ka BP in age. The study on the ice-wedge pseudomorphs showed that the air temperature was lowered by up to 6～7 ℃ in the source area of the Yellow River when the ice-wedge pseudomorphs and thawing-freezing folds developed.
基金Project supported by the Foundation Enhancement Planthe National Natural Science Foundation of China (Grant No. 61974116)
文摘The damage effect characteristics of GaAs pseudomorphic high electron mobility transistor(pHEMT)under the irradiation of C band high-power microwave(HPM)is investigated in this paper.Based on the theoretical analysis,the thermoelectric coupling model is established,and the key damage parameters of the device under typical pulse conditions are predicted,including the damage location,damage power,etc.By the injection effect test and device microanatomy analysis through using scanning electron microscope(SEM)and energy dispersive spectrometer(EDS),it is concluded that the gate metal in the first stage of the device is the vulnerable to HPM damage,especially the side below the gate near the source.The damage power in the injection test is about 40 dBm and in good agreement with the simulation result.This work has a certain reference value for microwave damage assessment of pHEMT.
文摘基于GaAs PHEMT工艺,设计制作了6-18 GHz驱动放大器单片电路。电路采用三级放大器拓扑结构,＋5 V单电源供电。第一级采用负反馈电路结构,级间采用有耗匹配结构实现工作带宽。为了实现较高的工作效率,对输出级器件进行了负载牵引仿真,确定了输出级器件的静态工作点和匹配结构。测试结果表明,在6-18 GHz,增益大于18 d B,输入输出回波损耗小于-10 d B,1 d B压缩点功率输出功率大于21 d Bm,饱和功率大于24 d Bm,功率附加效率大于25%,芯片尺寸为1.35 mm×1.00 mm。该电路具有频带宽、效率高、尺寸小等特点,可用于多种小型封装产品,具有广泛的应用前景。
