In this study, the physics-based device simulation tool Silvaco ATLAS is used to characterize the electrical properties of an AlGaN/GaN high electron mobility transistor （HEMT） with a U-type gate foot. The U-gate Al...In this study, the physics-based device simulation tool Silvaco ATLAS is used to characterize the electrical properties of an AlGaN/GaN high electron mobility transistor （HEMT） with a U-type gate foot. The U-gate AlGaN/GaN HEMT mainly features a gradually changed sidewall angle, which effectively mitigates the electric field in the channel, thus obtaining enhanced off-state breakdown characteristics. At the same time, only a small additional gate capacitance and decreased gate resistance ensure excellent RF characteristics for the U-gate device. U-gate AlGaN/GaN HEMTs are feasible through adjusting the etching conditions of an inductively coupled plasma system, without introducing any extra process steps. The simulation results are confirmed by experimental measurements. These features indicate that U-gate A1GaN/GaN HEMTs might be promising candidates for use in millimeter-wave power applications.展开更多
The instability of terahertz（THz）plasma waves in two-dimensional（2D）quantum electron gas in a nanometer field effect transistor（FET）with asymmetrical boundary conditions has been investigated.We analyze THz plas...The instability of terahertz（THz）plasma waves in two-dimensional（2D）quantum electron gas in a nanometer field effect transistor（FET）with asymmetrical boundary conditions has been investigated.We analyze THz plasma waves of two parts of the 2D quantum electron gas：gated and ungated regions.The results show that the radiation frequency and the increment（radiation power）in 2D ungated quantum electron gas are much higher than that in 2D gated quantum electron gas.The quantum effects always enhance the radiation power and enlarge the region of instability in both cases.This allows us to conclude that 2D quantum electron gas in the transistor channel is important for the emission and detection process and both gated and ungated parts take part in that process.展开更多
A novel matching method for simultaneous multi-target recognition is proposed by jointly considering target's prior scattering knowledge and the polarization parameters of radar echoes. The matching coefficients a...A novel matching method for simultaneous multi-target recognition is proposed by jointly considering target's prior scattering knowledge and the polarization parameters of radar echoes. The matching coefficients are calculated for the judgment. MATLAB simulations show that several targets can be accurately recognized simultaneously, and a high recognition probability can be achieved in Monte Carlo simulations. The total execution time can be remarkably reduced in the Field Programmable Gate Array (FPGA) implementation of the matching procedure.展开更多
GHz single-photon detector(SPD)is a crucial part in the practical high speed quantum key distribution(QKD)system.However,any imperfections in a practical QKD system may be exploited by an eavesdropper(Eve)to collect i...GHz single-photon detector(SPD)is a crucial part in the practical high speed quantum key distribution(QKD)system.However,any imperfections in a practical QKD system may be exploited by an eavesdropper(Eve)to collect information about the key without being discovered.The sine wave gating SPD(SG-SPD)based on InGaAs/InP avalanche photodiode,one kind of practical high speed SPD,may also contain loopholes.In this paper,we study the principle and characteristic of the SG-SPD and find out the filtering loophole of the SG-SPD for the first time.What is more,the proof-of-principle experiment shows that Eve could blind and control Bob's SG-SPD by exploiting this loophole.We believe that giving enough attention to this loophole can improve the practical security of the existing QKD system.GHz single-photon detector(SPD)is a crucial part in the practical high speed quantum key distribution(QKD)system.However,any imperfections in a practical QKD system may be exploited by an eavesdropper(Eve)to collect information about the key without being discovered.The sine wave gating SPD(SG-SPD)based on InGaAs/InP avalanche photodiode,one kind of practical high speed SPD,may also contain loopholes.In this paper,we study the principle and characteristic of the SG-SPD and find out the filtering loophole of the SG-SPD for the first time.What is more,the proof-of-principle experiment shows that Eve could blind and control Bob's SG-SPD by exploiting this loophole.We believe that giving enough attention to this loophole can improve the practical security of the existing QKD system.展开更多
All-optical XNOR and AND logic gates using four-wave mixing （FWM） and cross-gain modulation （XGM） in a single semiconductor optical amplifier （SOA） with improved dynamics are simultaneously realized. By numerica...All-optical XNOR and AND logic gates using four-wave mixing （FWM） and cross-gain modulation （XGM） in a single semiconductor optical amplifier （SOA） with improved dynamics are simultaneously realized. By numerical simulation, the effects of the input optical wave powers and injection current on the critical factors of the logic gate performances, such as the ON-OFF contrast ratio, the power-output level of the logic ＇1＇, and the difference between power outputs of the logic ＇1＇, are investigated in detail. In addition, the effect of the counter-propagating CW pump on the gain recovery is analysed.展开更多
A binary tree representation is designed in this paper for optimization of wave digital filter（WDF）implementation.To achieve this,an equivalent WDF model of the original circuit is converted into abinary tree repres...A binary tree representation is designed in this paper for optimization of wave digital filter（WDF）implementation.To achieve this,an equivalent WDF model of the original circuit is converted into abinary tree representation at first.This WDF binary tree can then be transformed to several topologies with the same implication,since the WDF adaptors have a symmetrical behavior on their ports.Because the WDF implementation is related to field programmable gate array（FPGA）resource usage and the cycle time of emulation,choosing aproper binary tree topology for WDF implementation can help balance the complexity and performance quality of an emulation system.Both WDF-FPGA emulation and HSpice simulation on the same circuit are tested.There is no significant difference between these two simulations.However,in terms of time consumption,the WDF-FPGA emulation has an advantage over the other.Our experiment also demonstrates that the optimized WDF-FPGA emulation has an acceptable accuracy and feasibility.展开更多
基金Project supported by the Major Program of the National Natural Science Foundation of China （Grant No. 60890191） and the National Key Basic Research Program of China （Grant No. 2010CB327503）.
文摘In this study, the physics-based device simulation tool Silvaco ATLAS is used to characterize the electrical properties of an AlGaN/GaN high electron mobility transistor （HEMT） with a U-type gate foot. The U-gate AlGaN/GaN HEMT mainly features a gradually changed sidewall angle, which effectively mitigates the electric field in the channel, thus obtaining enhanced off-state breakdown characteristics. At the same time, only a small additional gate capacitance and decreased gate resistance ensure excellent RF characteristics for the U-gate device. U-gate AlGaN/GaN HEMTs are feasible through adjusting the etching conditions of an inductively coupled plasma system, without introducing any extra process steps. The simulation results are confirmed by experimental measurements. These features indicate that U-gate A1GaN/GaN HEMTs might be promising candidates for use in millimeter-wave power applications.
基金supported by National Natural Science Foundation of China(No.10975114)
文摘The instability of terahertz（THz）plasma waves in two-dimensional（2D）quantum electron gas in a nanometer field effect transistor（FET）with asymmetrical boundary conditions has been investigated.We analyze THz plasma waves of two parts of the 2D quantum electron gas：gated and ungated regions.The results show that the radiation frequency and the increment（radiation power）in 2D ungated quantum electron gas are much higher than that in 2D gated quantum electron gas.The quantum effects always enhance the radiation power and enlarge the region of instability in both cases.This allows us to conclude that 2D quantum electron gas in the transistor channel is important for the emission and detection process and both gated and ungated parts take part in that process.
文摘A novel matching method for simultaneous multi-target recognition is proposed by jointly considering target's prior scattering knowledge and the polarization parameters of radar echoes. The matching coefficients are calculated for the judgment. MATLAB simulations show that several targets can be accurately recognized simultaneously, and a high recognition probability can be achieved in Monte Carlo simulations. The total execution time can be remarkably reduced in the Field Programmable Gate Array (FPGA) implementation of the matching procedure.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61605248 and 61505261)
文摘GHz single-photon detector(SPD)is a crucial part in the practical high speed quantum key distribution(QKD)system.However,any imperfections in a practical QKD system may be exploited by an eavesdropper(Eve)to collect information about the key without being discovered.The sine wave gating SPD(SG-SPD)based on InGaAs/InP avalanche photodiode,one kind of practical high speed SPD,may also contain loopholes.In this paper,we study the principle and characteristic of the SG-SPD and find out the filtering loophole of the SG-SPD for the first time.What is more,the proof-of-principle experiment shows that Eve could blind and control Bob's SG-SPD by exploiting this loophole.We believe that giving enough attention to this loophole can improve the practical security of the existing QKD system.GHz single-photon detector(SPD)is a crucial part in the practical high speed quantum key distribution(QKD)system.However,any imperfections in a practical QKD system may be exploited by an eavesdropper(Eve)to collect information about the key without being discovered.The sine wave gating SPD(SG-SPD)based on InGaAs/InP avalanche photodiode,one kind of practical high speed SPD,may also contain loopholes.In this paper,we study the principle and characteristic of the SG-SPD and find out the filtering loophole of the SG-SPD for the first time.What is more,the proof-of-principle experiment shows that Eve could blind and control Bob's SG-SPD by exploiting this loophole.We believe that giving enough attention to this loophole can improve the practical security of the existing QKD system.
基金Project supported by the National Natural Science Foundation of China （Grant No 60407001） and the National Science Foundation for Post-doctoral Scientists of China （Grant No 20060390246）.
文摘All-optical XNOR and AND logic gates using four-wave mixing （FWM） and cross-gain modulation （XGM） in a single semiconductor optical amplifier （SOA） with improved dynamics are simultaneously realized. By numerical simulation, the effects of the input optical wave powers and injection current on the critical factors of the logic gate performances, such as the ON-OFF contrast ratio, the power-output level of the logic ＇1＇, and the difference between power outputs of the logic ＇1＇, are investigated in detail. In addition, the effect of the counter-propagating CW pump on the gain recovery is analysed.
基金Supported by the National Natural Science Foundation of China(61271113)
文摘A binary tree representation is designed in this paper for optimization of wave digital filter（WDF）implementation.To achieve this,an equivalent WDF model of the original circuit is converted into abinary tree representation at first.This WDF binary tree can then be transformed to several topologies with the same implication,since the WDF adaptors have a symmetrical behavior on their ports.Because the WDF implementation is related to field programmable gate array（FPGA）resource usage and the cycle time of emulation,choosing aproper binary tree topology for WDF implementation can help balance the complexity and performance quality of an emulation system.Both WDF-FPGA emulation and HSpice simulation on the same circuit are tested.There is no significant difference between these two simulations.However,in terms of time consumption,the WDF-FPGA emulation has an advantage over the other.Our experiment also demonstrates that the optimized WDF-FPGA emulation has an acceptable accuracy and feasibility.
