In the case of through-the-wall localization of moving targets by ultra wideband (UWB) radars, there are applications in which handheld sensors equipped only with one transmitting and two receiving antennas are applied. Sometimes, the radar using such a small antenna array is not able to localize the target with the required accuracy. With a view to improve through-the-wall target localization, cooperative positioning based on a fusion of data retrieved from two independent radar systems can be used. In this paper, the novel method of the cooperative localization referred to as joining intersections of the ellipses is introduced. This method is based on a geometrical interpretation of target localization where the target position is estimated using a properly created cluster of the ellipse intersections representing potential positions of the target. The performance of the proposed method is compared with the direct calculation method and two alternative methods of cooperative localization using data obtained by measurements with the M-sequence UWB radars. The direct calculation method is applied for the target localization by particular radar systems. As alternative methods of cooperative localization, the arithmetic average of the target coordinates estimated by two single independent UWB radars and the Taylor series method is considered.

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In the past period, great efforts have been made to develop methods for through an obstacle detection of human vital signs such as breathing or heart beating. For that purpose, ultra-wideband (UWB) radars operating in the frequency band DC-5 GHz can be used as a proper tool. The basic principle of respiratory motion detection consists in the identification of radar signal components possessing a significant power in the frequency band 0.2-0.7 Hz (frequency band of human respiratory rate) corresponding to a constant bistatic range between the target and radar. To tackle the task of detecting respiratory motion, a variety of methods have been developed. However, the problem of person localization based on his or her respiratory motion detection has not been studied deeply. In order to fill this gap, an approach for multiple person localization based on the detection of their respiratory motion will be introduced in this chapter.

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The person localization by ultra-wideband (UWB) sensors is a challenging field attracting researchers worldwide. Whereas the issue of the person localization in 2dimensional space (2D) has been discussed in many articles, only a few papers have been devoted to the people localization in 3-dimensional space (3D). Combining two 3D localization methods a new approach to the person localization in 3D can be obtained to fill this gap. The new 3D localization method introduced in this paper is referred to as the Taylor series based localization method (TSM). This method combines the 3D-2D method of object localization in 3D with the conventional method of Taylor series. The performance properties of the introduced TSM will be illustrated via the experimental scenario intent on the through-the-wall localization of a moving person by a multistatic UWB radar system. D. Kocur et al. Determining the Positions of the Moving Persons in 3D Space by UWB Sensors -46 -fine range resolution based on time-of-arrival (TOA) measurement [3], UWB sensors can provide object localization with high accuracy as well. Moreover, signals transmitted by UWB radars are extremely low-power. As results, they produce only low-level interference of narrowband communication infrastructure and thus they can more easily coexist with such communication systems. These and further unique properties of UWB sensors (comprehensively summarized, e.g. in [1]) have been the impetus in the last years for relatively extensive development of applications of UWB localization systems. Rescue and security operations, critical infrastructures monitoring [1], [4], [5], [6], senior monitoring within their dwellings [7], [8], baby monitoring (e.g. detection of sudden death syndrome), etc. are just a few examples of such applications. Moreover, due to the development of communication and sensor networks, smart-home, smart-cities, Internet of Things and low-cost UWB sensor systems, it is expected the growth of requests for contactless monitoring of people in the near future. Motivated by these findings we have focused our research on moving people monitoring (e.g. [9], [10], [11], [12], etc.) by means of UWB radars. In this area, great attention has been devoted to the localization of persons through a vertical wall in 2-dimensional (2D) and 3-dimensional space (3D) (e.g. [1], [13]) as well as through-the-floor localization of persons in 3D [10] or to the localization of persons situated behind a corner [14].

Ultra-wideband (UWB) radars are sensors allowing to track people in critical environments and situations. The results reached by single UWB sensors for such applications have shown that they are able to detect and track a person very well in a single person scenario. However, in multiple moving person scenarios, the ability of a single UWB sensor to detect several persons is usually significantly reduced. This is caused by a mutual shielding among people. In this paper, we will deal with the mutual shielding effect and its impacts, as well as with the methods of improving multiple moving person tracking by UWB radars. Firstly, we will provide a comprehensive description of the mutual shielding effect. Then, based on its analyses, we will state three complementary approaches created by the authors of this paper to reduce its impacts. They include an enhancement of the low-level echo of the targets, radar antenna array positioning at a convenient height, UWB sensor network application and, finally, their mutual combinations. The properties of those approaches will be demonstrated by two experimental measurements aimed at through wall tracking of two and three people, respectively. The results obtained in the experiments will illustrate the mutual shielding effect and the potential of the methods we have proposed to reduce its impacts.