Rutkowski Adam, Kawalec Adam
Faculty of Electronics, Military University of Technology, ul. Gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland.
Sensors (Basel). 2020 Sep 11;20(18):5186. doi: 10.3390/s20185186.
Locating active radars in real environmental conditions is a very important and complex task. The efficiency of the direction finding (DF) of ground-based radars and other microwave emitters using unmanned aerial vehicles (UAV) is dependent on the parameters of applied devices for angle location of microwave emitters, and on the construction and modes of operation of the observed transmitting antenna systems. An additional factor having the influence on DF of the radar, when are used systems installed on the UAV, is the rotation of the antenna of a radar. The accuracy of estimation of direction of any microwave transmitter is determined by the terrain properties that surround the transmitter and the objects reflecting microwave signals. The exemplary shapes of the radar antenna patterns and the associated relationships with the probability of remotely detecting the radar and determining its bearings are described. The simulated patterns of the signals received at an emitter-locating device mounted on a UAV and the expected results of a monopulse DF based on these signals are presented. The novelty of this work is the analysis of the DF efficiency of radars in conditions where intense multi-path phenomena appear, and for various amplitudes and phases of the direct signal and multi-path signals that reach the UAV when assuming that so-called simple signals and linear frequency modulation (LFM) signals are transmitted by the radar. The primary focus is on multi-path phenomenon, which can make it difficult, but not entirely impossible, to detect activity and location of radar with a low-flying small UAV and using only monopulse techniques, that is, when only a single pulse emitted by a radar must be sufficient to DF of this radar. Direction of arrival (DOA) algorithms of signals in dense signal environment were not presented in the work, but relevant suggestions were made for the design of such algorithms.
在实际环境条件下定位有源雷达是一项非常重要且复杂的任务。使用无人机（UAV）对地面雷达和其他微波发射器进行测向（DF）的效率取决于用于微波发射器角度定位的应用设备参数，以及所观测发射天线系统的结构和运行模式。当使用安装在无人机上的系统时，影响雷达测向的另一个因素是雷达天线的旋转。任何微波发射器方向估计的准确性取决于发射器周围的地形特性以及反射微波信号的物体。描述了雷达天线方向图的典型形状以及与远程探测雷达并确定其方位概率的相关关系。给出了安装在无人机上的发射器定位设备接收到的信号模拟方向图以及基于这些信号的单脉冲测向预期结果。这项工作的新颖之处在于分析了在出现强烈多径现象的条件下，以及在假设雷达发射所谓简单信号和线性调频（LFM）信号时，到达无人机的直达信号和多径信号的各种幅度和相位情况下雷达的测向效率。主要关注点是多径现象，它可能会使使用低空小型无人机并仅采用单脉冲技术（即当雷达发射的单个脉冲必须足以对该雷达进行测向时）检测雷达的活动和位置变得困难，但并非完全不可能。本文未给出密集信号环境中信号的到达方向（DOA）算法，但对这类算法的设计提出了相关建议。
