2022, 51(8): 20220453.
doi: 10.3788/IRLA20220453
2022, 51(8): 20220493.
doi: 10.3788/IRLA20220493
2022, 51(5): 20220276.
doi: 10.3788/IRLA20220276
2022, 51(3): 20210859.
doi: 10.3788/IRLA20210859
2022, 51(11): 20220660.
doi: 10.3788/IRLA20220660
2022, 51(10): 20220596.
doi: 10.3788/IRLA20220596
2021, 50(5): 20211025.
doi: 10.3788/IRLA20211025
With its unique time-frequency characteristics and integrated advantages, micro combs have gradually become the cornerstone of modern information system. Recently, all fiber microcavity combs made a progress. Researchers from the University of Electronic Science and Technology of China and Nanjing University realized the generation of laser, Kerr and Brillouin optical frequency combs by using ultra-high Q-value fiber Fabry Perot resonators. They demonstrate unique advantages such as low loss, dynamic tunability and ultrahigh stability, may play new potentials in timing-standard, communication, microwave and sensing applications for fiber systems.
2020, 49(4): 0404005.
doi: 10.3788/IRLA202049.0404005
Terahertz passive imaging technology has many unique advantages and has become an important research direction in the field of security inspection. In order to further improve the imaging performance and practicability of the terahertz passive imaging system, the performance of a terahertz passive imaging system based on opto-mechanical scanning developed by our laboratory was studied. By exploring the influence of different system parameters and experimental conditions including its imaging speed, distance and the status of detector on the performance of imaging system such as the image resolution and background noise, the optimized system parameters were obtained. At the same time, the performance of imaging system to detect the human body hiding the metal objects was explored. It was shown that the system was suitable for the security inspection of human body. The experimental results show that the imaging distance of the terahertz passive imaging system is within the range of 1.5–2.5 m in front of imager, that is, its depth of field is about 1 m. The imaging speed of system is 2–4 seconds per frame. Moreover, the operating level and gain of detector have a great impact on image sharpness and system noise. There exists an optimized operating state of detector. Under the optimized condition, the clear terahertz images can be achieved and the resolution of target was 1.5–2 cm. Our imaging system can clearly detect metal objects hidden under human body’s clothes and substances with strong absorption on terahertz waves.
2020, 49(4): 0403001.
doi: 10.3788.IRLA202049.0403001
Panoramic laser fuze usually calculates the optimal initiation time and initiation azimuth only based on single measured target direction and distance, the calculation accuracy is low. On the other hand, fuze can not distinguish the authenticity of targets, it is easy to cause "false alarm" or accidental bombing. Based on the working principle of the synchronous scanning panoramic pulse laser fuze, the direction, distances and position coordinates of multiple detection points were analyzed. The target velocity model based on multiple detection points were established, which can calculate the target speed and judge whether the target was true. The geometric center position of the target feature was solved, and the optimal initiation time and azimuth calculation model were established to obtain the maximum damage effectiveness of the warhead. The influence factors of the optimal initiation time and azimuth were analyzed. The research can provide a reference for the target identification and directional initiation of the panoramic laser fuze.
2020, 49(4): 0403002.
doi: 10.3788/IRLA202049.0403002
The laser fuze can realize omnidirectional detection of missile targets through the circumferential multi-channel layout, its active-rotational-narrow pulse detection method can obtain the information about missile-target distance, miss azimuth angle and target type. At the same time, due to the characteristics of narrow beam and no side lobes, the fuze initiation zone has a small distribution area. All of these factors provide an important technical approach for efficient fuze-warhead coordination. Based on the analysis of the influence factors of air-defense missile fuze-warhead coordination, a fuze-warhead system scheme with eight-channel circumferential laser fuze was designed, combined with missile-target distance, miss azimuth, and target type. The fuze-warhead coordination simulation results in conditions of typical encounter parameters indicate that, the kill probability of single missile could be obtained to a maximum of 10% with the laser fuze information. It is useful for optimal design.
2020, 49(4): 0403003.
doi: 10.3788/IRLA202049.0403003
Aiming at optimal detonation controlling of directional warhead fuze, detonation control simulation for dodecagon-detection laser fuze was presented. Based on dodecagon-detection model, the detonation orientation was controlled by discriminating target orientation. Combining with target vulnerability model, effect of delay time on damage was simulated and analyzed on different trajectories. The simulation results show that it is very important to match the parameters such as fuze delay time, miss distance and fragment fly scattering angle for high-speed small targets in air. When delay time is no more than 2 ms, the average damage probability, if miss distance is within 8 m, is more than 0.6, and is less than 0.5 if miss distance is over 10 m. The model can comprehensively analyze the damage effects with different delay time and miss distances.
2020, 49(4): 0403004.
doi: 10.3788/IRLA202049.0403004
Aerosol-interference is a serious interference source for active optical target-detection device (AOTD) when it is used in lower sky or super low sky. When AOTD in a vehicle passes through aerosol, it may be wrong armed, even give out execution signal before right time. In order to increase the ability in aerosol environment, how the AOTD worked and how the aerosol interfered the AOTD were analyzed. It also showed out the techniques of anti-aerosol-interference used in engineering. The general techniques for anti-aerosol-interference were settings of cut-off distance method, weaken methods by optical parts, optical field restraining method, cancellation by symmetric views, setting reference view field, body recognition method, composite with Ka detectors, decreasing the width of transmitted pulse, image recognition method et al. Among these methods, the multimode detection method was a valuable way. Effects of different anti-interference methods were listed, the results shows integrated application of all the methods can increase the ability of AOTD.
2020, 49(4): 0403005.
doi: 10.3788/IRLA202049.0403005
The detection ability of laser fuze is easily disturbed by smoke, which causes false alarm. In order to study on the backscattering characteristics of pulsed laser fuze in smoke, the relevant model based on Mie scattering theory and Monte Carlo method was established, and the backscattering signal in smoke was simulated using 905 nm pulsed laser. To verify the accuracy of the model, the actual peak voltage was compared with the simulated normalized intensity and correlation analysis was conducted. Then, the backscattering characteristics of the pulsed laser fuze under different smoke concentrations, length of pipes and distances were analyzed. Finally, the influence of different smoke environment was obtained. The results can provide support for the anti-smoke interference of the pulsed laser fuze.
2020, 49(4): 0403006.
doi: 10.3788/IRLA202049.0403006
In order to analyze the performance of coherent laser fuze under cloud and fog interference, the detection model of coherent laser fuze in cloud and fog was created based on Mie scattering theory and Monte Carlo method. Through simulation, the echoes of coherent laser fuze were obtained in various scenes. The time-domain and frequency-domain characteristics of echoes were analyzed, as well as the influence of cloud and fog visibility, detection position, and detection angle on echoes. The results show that the coherent laser fuze can accurately identify the target by using the frequency-domain characteristics, and is not easily affected by factors such as cloud and fog visibility, detection position, and detection angle. The results demonstrate the excellent detection performance of coherent laser fuze in cloud and fog.
2020, 49(4): 0403007.
doi: 10.3788/IRLA202049.0403007
In view of the problem that laser fuze is easily interfered by fog and smoke, a new laser fuze anti-interference method based on pulsed width modulation technique was proposed. The fog echo signal power of different pulse width was computed, and the variation of echo signal power under the influence of transmitted pulse duration was given. The echo signal power ratio in different fog and aerosols environment was analyzed by using different pulse width to detect. The experiment results show that by using different pulse width to detect, the ratio of backscattering power is usually more than 3. Therefore, this method can be used to improve anti-interference ability of laser fuze.
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