Object coordinate determination by the impulse GPR with a Tx + 4Rx antenna system

Landmine contamination is a threat to the safety of human life and health and hinders economic activity in vast areas. The problem of humanitarian demining became especially important due to the war waged by the Russian Federation in Ukraine on February 24. According to experts, 300,000 square meters of the territory of Ukraine are currently mined. Cleaning such an area requires tremendous effort. To facilitate the detection and removal of mines, specialized equipment is being created. Partly it was reported at the 8th Mine Action Technology Workshop in Geneva, 2 - 4 November 2021. Several new methods were reported in the [1]. The authors of the international project G5731 [2], implemented within the framework of NATO’s “Science for Peace and Security Program”, are exploring the possibility of creating a team of robots capable of reliably identifying and locating mines and other explosive devices hidden in the ground [3]. One of the members of the robot team is the Jackal robotic platform [4], equipped with ultra-wideband pulse ground penetrating radar (GPR) designed to detect and determine the coordinates of objects located below the soil surface. In the previous multi-year project # G5014, in the framework of the NATO Science for Peace and Security Program: “Holographic and Impulse Subsurface Radar for Landmine and IED Detection” [5], we have shown that it is possible to calculate the coordinates of underground objects using an antenna system consisting of one radiating (Tx) and four receiving (Rx) antennas (1Tx + 4Rx) [6], (Fig. 1). To do this, it is sufficient to determine the time of flight (TOF) of the probing signal from the radiating antenna to the subsurface object and then back to each of the four receiving antennas. Therefore, a necessary and sufficient condition for the detection (and determination of the location) of the subsurface object is to obtain the results of measurements of all four TOFs by all four receiving channels. However, in the existing algorithm, the absence of the received signal even in one of the four receiving channels leads to the inability to calculate the coordinates of the target and, therefore, to miss the target, which reduces the probability of mines detection. The reason for the loss of signal in the receiving channel can be, for example, a long distance from the object to one of the receiving antennas, which reduces the amplitude of the received antenna signal below the sensitivity threshold of the receiver, or a strong interfering signal near radar and others. As a result, the signal reflected by the object may not be detected.