# The UWB Radar Application in the Aviation Security Systems
## 2 Materials and Methods
### Localization of the Target by the Straight-Line Method for Two Independent Radar Sets
#### 2.1.1 Description of the Place of the Experiment and the Target Movement  
The movement of a person within the room behind a concrete obstacle is shown in Figure 1. The position of a moving person was determined by two independent UWB radar systems. Radar parameters are as follows [29]:  
**M-sequence UWB radar RS1**  
Radar clock frequency: 13 GHz; frequency bandwidth: 6.3 GHz; pulse response length in time: 4095 samples/315 ns; maximum range: 47 m; radiated power: 10 mW;  
**M-sequence UWB radar RS 2**  
Radar clock frequency: 4.5 GHz; frequency bandwidth: 2.25 GHz; pulse response length in time: 511 samples/114 ns; maximum range: 17 m; radiated power: 1 mW.  
The antenna system of the 1 st radar set (RS1), consisting of a transmitting antenna and two receiving antennas, was placed behind a 0.3 m thick wall. The transmitting antenna of the 1 st radar set RS1 (TxA) was placed at the beginning of the selected coordinate system  
Figure 1: Deployment of radar systems and movement of the target in the building.  
in the middle between the receiving antennas (RxA 1,2) placed symmetrically, at a distance of 0.175 m from the transmitter. The antenna system of the 2 nd RS2 radar set, consisting of a transmitting antenna and two receiving antennas, was placed behind the 0.43 m thick wall. The transmitting antenna of the 2 nd radar set RS2 (TxB) was placed at the height of 3.14 m behind the left wall rooms in the middle between the receiving antennas (RxB 1,2) placed symmetrically, at a distance of 0.43 m from the transmitter.  
We determined the position of a person who moved from the position P1 to positions P2, P3, P4, and from P4 to the position P1. To obtain trace estimation as a sequence TOA, the radar signal processing steps are described in [29]. We divided the experiment and signal processing of UWB radars into the following stages: placement of the radar on the walls of the room according to Figure 1; signal pre-processing, which includes synchronization setup, and deconvolution (see Section 2.1.2); target detection; target track estimate. In our paper, we describe the target track estimate in detail. The goal of localization is to determine the position of the target in a defined coordinate system by the usual method of locating targets, which consists [33] of the following steps. In the first step, an estimation of the distance between the target and a certain number of reference sensors is performed. Subsequently, using the distance estimation, the target position is estimated using the selected localization method. We used the principle of distance estimation to measure the time of arrival of the signal (Time of Arrival, TOA). TOA means the time interval between the transmission time and the signal reception time. The name is used for both One-Way Propagation Time (OWPT) and Round-Trip Propagation Time (RTPT) transmission [34]. In this case, the distance R between the target and the antenna is given by the product of half (1/2) of the signal propagation time and the signal propagation rate in the monitored environment. In our case, we used the bistatic configuration. Separate antennas for transmitting and receiving are at a certain distance from each other. The measurement makes it possible to construct an ellipse in 2D space (or an ellipsoid in 3D space) with focal points in the coordinates of the transmitting and receiving antennas. When locating a person, it is possible to determine their coordinates by finding the intersection of ellipsoids in 3D space. A condition for the functionality of TOA systems is the need for time synchronization between the target and the transmitting and receiving antennas in bidirectional RTPT transmission [34]. Since the transmitting antenna RS1 and the receiving antennas RxA 1,2 are close to each other, it is not a problem to ensure time synchronization between these antennas. Similar conclusions apply to the RS2, RxB 1,2 kit.