The rail temperature rises when the linear eddy current brake of high-speed train is working, which may lead to a change of rail physical characteristics or an effect on train operations. Therefore, a study concerning...The rail temperature rises when the linear eddy current brake of high-speed train is working, which may lead to a change of rail physical characteristics or an effect on train operations. Therefore, a study concerning the characteristics of rail temperature rise caused by eddy current has its practical necessity. In the research, the working principle of a linear eddy current brake is introduced and its FEA model is established. According to the generation mechanism of eddy current, the theoretical formula of the internal energy which is produced by the eddy current is deduced and the thermal load on the rail is obtained. ANSYS is used to simulate the rail temperature changes under different conditions of thermal loads. The research result shows the main factors which contribute to the rising of rail temperature are the train speed, brake gap and exciting current. The rail temperature rises non-linearly with the in- crease of train speed. The rail temperature rise curve is more sensitive to the exciting current than the air gap. Moreover, the difference stimulated by temperature rising between rails of 60 kg/m and 75 kg/m is presented as well.展开更多
A high linearity current communicating passive mixer including the mixing cell and transimpedance amplifier(TIA) is introduced.It employs the resistor in the TIA to reduce the source voltage and the gate voltage of th...A high linearity current communicating passive mixer including the mixing cell and transimpedance amplifier(TIA) is introduced.It employs the resistor in the TIA to reduce the source voltage and the gate voltage of the mixing cell.The optimum linearity and the maximum symmetric switching operation are obtained at the same time.The mixer is implemented in a 0.25μm CMOS process.The test shows that it achieves an input third-order intercept point of 13.32 dBm,conversion gain of 5.52 dB,and a single sideband noise figure of 20 dB.展开更多
A high linearity current mode multiplier/divider （CMM/D） with a wide dynamic range is presented. The proposed CMM/D is based on the voltage-current characteristic of the diode, thus wide dynamic range is achieved. I...A high linearity current mode multiplier/divider （CMM/D） with a wide dynamic range is presented. The proposed CMM/D is based on the voltage-current characteristic of the diode, thus wide dynamic range is achieved. In addition, high linearity is achieved because high accuracy current mirrors are adopted and the output current is insensitive to the temperature and device parameters of the fabrication process. Furthermore, no extra bias current for all input signals is required and thus power saving is realized. With proper selection of establishing the input terminal, the proposed circuit can perform as a mulfifunction circuit to he operated as a multiplier/divider, without changing its topology. The proposed circuit is implemented in a 0.25μm BCD process and the chip area is 0.26 ~ 0.24 mm2. The simulation and measurement results show that the maximum static linearity error is 4-1.8% and the total harmonic distortion is 0.4% while the input current ranges from 0 to 200 μA.展开更多
基金project is supported by the Fundamental Research Funds for the Central Universities(No.2860219030)Foundation of State Key Laboratory of Traction Power,Southwest Jiaotong University(No. TPL1308)
文摘The rail temperature rises when the linear eddy current brake of high-speed train is working, which may lead to a change of rail physical characteristics or an effect on train operations. Therefore, a study concerning the characteristics of rail temperature rise caused by eddy current has its practical necessity. In the research, the working principle of a linear eddy current brake is introduced and its FEA model is established. According to the generation mechanism of eddy current, the theoretical formula of the internal energy which is produced by the eddy current is deduced and the thermal load on the rail is obtained. ANSYS is used to simulate the rail temperature changes under different conditions of thermal loads. The research result shows the main factors which contribute to the rising of rail temperature are the train speed, brake gap and exciting current. The rail temperature rises non-linearly with the in- crease of train speed. The rail temperature rise curve is more sensitive to the exciting current than the air gap. Moreover, the difference stimulated by temperature rising between rails of 60 kg/m and 75 kg/m is presented as well.
基金supported by the National High Technology R&D Program ofChina(No.2011AA040102)the National Science and Technology Major Project ofthe Ministry of Science and Technology of China(No.2009ZX01031-002-008-002)
文摘A high linearity current communicating passive mixer including the mixing cell and transimpedance amplifier(TIA) is introduced.It employs the resistor in the TIA to reduce the source voltage and the gate voltage of the mixing cell.The optimum linearity and the maximum symmetric switching operation are obtained at the same time.The mixer is implemented in a 0.25μm CMOS process.The test shows that it achieves an input third-order intercept point of 13.32 dBm,conversion gain of 5.52 dB,and a single sideband noise figure of 20 dB.
基金Project supported by the Important National S&T Special Project of China(Nos.2009ZX01031-003-003,51308020305)
文摘A high linearity current mode multiplier/divider （CMM/D） with a wide dynamic range is presented. The proposed CMM/D is based on the voltage-current characteristic of the diode, thus wide dynamic range is achieved. In addition, high linearity is achieved because high accuracy current mirrors are adopted and the output current is insensitive to the temperature and device parameters of the fabrication process. Furthermore, no extra bias current for all input signals is required and thus power saving is realized. With proper selection of establishing the input terminal, the proposed circuit can perform as a mulfifunction circuit to he operated as a multiplier/divider, without changing its topology. The proposed circuit is implemented in a 0.25μm BCD process and the chip area is 0.26 ~ 0.24 mm2. The simulation and measurement results show that the maximum static linearity error is 4-1.8% and the total harmonic distortion is 0.4% while the input current ranges from 0 to 200 μA.
