-
在引信位于云雾内部的场景中,目标为一块反射率0.3的朗伯体平板,位于云雾内部,与引信相向飞行,飞行速度为340 m/s,脱靶距离为5 m;云雾粒径范围为0.1~50 μm,能见度分为10 、30 、50 和80 m四档,以20 m/s的速度与目标同向移动;引信以60°倾角(探测光束与弹体之间的夹角)发射波长为1 550 nm的激光对目标进行探测,激光束在子午方向和弧矢方向的发散角均为5 mrad,激光发射与接收共用一套光学系统,孔径为25.4 mm,子午方向和弧矢方向的接收视场角均为21 mrad。仿真主要参数值如表1所示,仿真场景如图2所示。
Simulation parameters Value Simulation parameters Value Dip angle of fuze/(°) 60 Laser wavelength/nm 1 550 Laser divergence angle/mrad 5 Receiving field angle/mrad 21 Visibility of cloud and fog/m 10, 30 50, 80 Optical lens diameter/mm 25.4 Particle diameter of cloud and fog/μm 0.1–50 Speed of cloud and fog/m•s–1 20 Complex index of refraction 1.317–8.55×10–5i Target distance/m 5 Target reflectivity 0.3 Target speed/m•s–1 340 Table 1. Main parameters of model when the fuze is located cloud and fog
当云雾能见度分别为10 、30 、50 和80 m时,相干激光引信接收到的回波信号的时域波形与频域波形如图3所示。观察图3中的时域波形,当云雾能见度为10 m时,目标回波完全被云雾回波淹没,回波信号无法反映引信周围的目标与环境状态;当云雾能见度依次增大至30 、50 和80 m时,目标回波逐渐增强,回波信号呈现出双波峰特征,但是考虑到体目标也可能产生此类回波,因此引信依然无法根据回波信号进行准确判断。再观察图3中的频域波形,四种能见度条件下的回波信号在频域上均出现了两个清晰的点频信号:第一个点频信号位于13 MHz处,是由云雾回波形成的;第二个点频信号位于219 MHz处,显然是由目标回波形成的;目标回波与云雾回波在频域上差异明显,极易分辨。上述结果表明,在低能见度环境和低信噪比条件下,相干激光引信可以利用频域特征准确识别出目标和云雾。
-
在引信位于云雾外部的场景中,云雾边界距离引信5 m,目标脱靶距离为10 m,其余状态与引信位于云雾内部时的场景相同。仿真场景如图4所示。
图5为四种云雾能见度条件下,相干激光引信位于云雾外部时回波信号的时域波形和频域波形。图5中的结果与图2相比,引信回波信号的时域波形在时刻、幅度等方面均发生了变化,而频域波形只有信号幅度出现了一些变化,频点位置未发生改变。上述结果表明,引信、目标和云雾之间的位置关系,不会影响相干激光引信对目标和云雾的准确识别。
-
探测角度是指引信发射的激光束与目标飞行方向之间的夹角,其对引信回波的频域特征具有重要影响。当目标飞行速度为340 m/s时,目标回波频移与与探测角度的关系如图6所示,图中阴影区域为云雾移动速度20 m/s时的云雾回波频移范围。观察图6,当探测角度为0°或180°,即探测光束与目标飞行方向平行时,目标回波的频移量最大,为438.7 MHz;当探测角度为90°,即探测光束与目标飞行方向垂直时,目标回波的频移量最小,为0 Hz。当探测角度在86.6°~93.4°这一狭窄区间时,目标回波的频移落入云雾回波频移范围(0~25.8 MHz)内,即目标回波与云雾回波可能在频域发生混叠,导致引信无法准确区分目标与云雾;而在其他区间内,目标回波的频移均超过了云雾回波频移最大值,即目标回波与云雾回波在频域上区分明显,引信可准确识别出目标。上述结果表明,在绝大部分探测角度下,相干激光引信可利用频域特征区分出目标与云雾。
Study on echo characteristics of coherent laser fuze in cloud and fog
doi: 10.3788/IRLA202049.0403006
- Received Date: 2020-01-02
- Rev Recd Date: 2020-02-20
- Publish Date: 2020-04-24
-
Key words:
- coherent laser fuze /
- cloud and fog /
- echo characteristics /
- simulation
Abstract: 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.