Light detection and ranging (LIDAR) based on time of flight (TOF) method is widely used in many fields related to distance measurement. LIDAR generally uses laser diode (LD) to emit the pulsed laser with high peak pow...Light detection and ranging (LIDAR) based on time of flight (TOF) method is widely used in many fields related to distance measurement. LIDAR generally uses laser diode (LD) to emit the pulsed laser with high peak power and short duration to ensure a large distance measurement range and eye safety. To achieve this goal, we propose a pulsed LD drive method producing the drive current with high peak and narrow pulse width. We analyze the key issues and related theories of the drive current generation based on this method and design an LD driver. A model of drive current generation is established and the influence of operating frequency on drive current is discussed. The LD driver is simulated by software and verified by experiments. The working frequency of the driver changes from 20 kHz to 100 kHz and the charging voltage is set at 130 V. The current produced by this driver has a duration of 8.8 ns and a peak of about 35 A, and the peak output optical power of the LD exceeds 75 W.展开更多
A communication system based on an ultraviolet(UV) laser at 266 nm is presented to improve the communication distance. The pulse frequency-shift keying(FSK) modulation scheme is studied and improved in order to reduce...A communication system based on an ultraviolet(UV) laser at 266 nm is presented to improve the communication distance. The pulse frequency-shift keying(FSK) modulation scheme is studied and improved in order to reduce the bit error rate(BER), and is put into practice on a field programmable gate array(FPGA). The mathematical models of the modulation and demodulation are established. A test platform is set up to measure the energy density and pulse response under different distances and receiver elevation angles. It is shown that the omnibearing communication can be realized, and the bit rate is limited to 12.5 Mbit/s. The BER is estimated to be less than 10-7 at distance of 300 m in line-of-sight(LOS) communication model and to be less than 10-6 at distance of 80 m in non-line-of-sight(NLOS) communication model.展开更多
In order to improve the measurement accuracy of weapons, ultra-wideband(UWB) inverse synthetic aperture radar(ISAR) imaging of high-speed moving targets in short-range is studied. In the scheme, because the positions ...In order to improve the measurement accuracy of weapons, ultra-wideband(UWB) inverse synthetic aperture radar(ISAR) imaging of high-speed moving targets in short-range is studied. In the scheme, because the positions of scatters vary with the radar line-of-sight(LOS) angle when the high-speed target is passing through the closest point of the approach, the concept of equivalent scattering point(ESP) is proposed. The Hough transform is employed to implement ESP motion parameter estimation,while the target translational motion is compensated by using the ESP time delay, and the angle spanned by the target is estimated by utilizing geometric relationship of ESP motion. Finally, the twodimensional image of the target is restructured by using the near field time-domain back-projection algorithm. Simulation results confirm that the proposed method is efficient.展开更多
This paper examines the effects of current and conductance noises in a minimal Hodgkin- Huxley type model of a cold receptor neuron. Current noise enters the membrane equation directly while conductance noise is propa...This paper examines the effects of current and conductance noises in a minimal Hodgkin- Huxley type model of a cold receptor neuron. Current noise enters the membrane equation directly while conductance noise is propagated through the activation variables. Compared with common used interspike interval method, ISI-distance is a simple complementary approach to measure the different effects of current and conductance noises. ISI-distance extracts information from the interspike intervals by evaluating the ratio of instantaneous firing rates, which is parameter-free, time scale-independent and easy to visualize. Simulation results show that the most significant differences between different noise implementations in a pacemaker-like tonic firing regime at the transition to chaotic burst discharges.展开更多
基金National Key Research and Development Plan(No.2017YFF0204800)Natural Science Foundation of Tianjin(No.17JCQNJC01100)+3 种基金National Natural Science Foundation of China(Nos.61501319,51775377,61505140)Young Elite Scientists Sponsorship Program by Cast of China(No.2016QNRC001)Open Project of Key Laboratory of Micro Opto-electro Mechanical System Technology(No.MOMST2015-7)Open Project from Photoelectric Information and Instrument-Engineering Research Center of Beijing,Tianjin University,Ministry of Education(No.GD2015007)
文摘Light detection and ranging (LIDAR) based on time of flight (TOF) method is widely used in many fields related to distance measurement. LIDAR generally uses laser diode (LD) to emit the pulsed laser with high peak power and short duration to ensure a large distance measurement range and eye safety. To achieve this goal, we propose a pulsed LD drive method producing the drive current with high peak and narrow pulse width. We analyze the key issues and related theories of the drive current generation based on this method and design an LD driver. A model of drive current generation is established and the influence of operating frequency on drive current is discussed. The LD driver is simulated by software and verified by experiments. The working frequency of the driver changes from 20 kHz to 100 kHz and the charging voltage is set at 130 V. The current produced by this driver has a duration of 8.8 ns and a peak of about 35 A, and the peak output optical power of the LD exceeds 75 W.
基金supported by the National Natural Science Foundation of China(No.11075226)the Natural Science Foundation of Chongqing(No.cstc2014jcyjA 90010)
文摘A communication system based on an ultraviolet(UV) laser at 266 nm is presented to improve the communication distance. The pulse frequency-shift keying(FSK) modulation scheme is studied and improved in order to reduce the bit error rate(BER), and is put into practice on a field programmable gate array(FPGA). The mathematical models of the modulation and demodulation are established. A test platform is set up to measure the energy density and pulse response under different distances and receiver elevation angles. It is shown that the omnibearing communication can be realized, and the bit rate is limited to 12.5 Mbit/s. The BER is estimated to be less than 10-7 at distance of 300 m in line-of-sight(LOS) communication model and to be less than 10-6 at distance of 80 m in non-line-of-sight(NLOS) communication model.
基金supported by the National Natural Science Foundation of China(61421001)
文摘In order to improve the measurement accuracy of weapons, ultra-wideband(UWB) inverse synthetic aperture radar(ISAR) imaging of high-speed moving targets in short-range is studied. In the scheme, because the positions of scatters vary with the radar line-of-sight(LOS) angle when the high-speed target is passing through the closest point of the approach, the concept of equivalent scattering point(ESP) is proposed. The Hough transform is employed to implement ESP motion parameter estimation,while the target translational motion is compensated by using the ESP time delay, and the angle spanned by the target is estimated by utilizing geometric relationship of ESP motion. Finally, the twodimensional image of the target is restructured by using the near field time-domain back-projection algorithm. Simulation results confirm that the proposed method is efficient.
文摘This paper examines the effects of current and conductance noises in a minimal Hodgkin- Huxley type model of a cold receptor neuron. Current noise enters the membrane equation directly while conductance noise is propagated through the activation variables. Compared with common used interspike interval method, ISI-distance is a simple complementary approach to measure the different effects of current and conductance noises. ISI-distance extracts information from the interspike intervals by evaluating the ratio of instantaneous firing rates, which is parameter-free, time scale-independent and easy to visualize. Simulation results show that the most significant differences between different noise implementations in a pacemaker-like tonic firing regime at the transition to chaotic burst discharges.
