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The article concerns the estimation of land deformation in an area of copper mining using the Persistent Scatterer Interferometry (PSI) technique and C-band data coming from the Sentinel-1 satellite. The aim of the work is a comparison of two different PSI approaches exploiting passive corner reflectors deployed pairwise, oriented towards the satellites in ascending and descending orbits. The comparison was done in the line of sight geometry. In addition, a validation was carried out using GNSS measurements. The results achieved using the two PSI approaches are consistent and mutually coherent. They are also congruent with observations from GNSS stations. These results proves that the method proposed to identify pixels on multi-looked images is correct. In addition, the intermediary results on the corner reflectors shows that their responses, in terms of dispersion of amplitude and the coherence, is slightly different. This needs to be further studied.

This work examines how reflections from various reflective surfaces affect the reception of RF electromagnetic waves and how the latter impacts wireless power transmission. The frequency range used was 469.5 MHz to 773.5 MHz, and three reflective materials of almost 20% variation in the reflection coefficient were tested with a Yagi–Uda antenna at the receiving end. Additionally, the orientation of the antenna was changed in terms of elevation and azimuthal angles. The results were then assessed, and a conclusion was drawn.

This paper is focused on SAR interferometry for deformation monitoring, based on the use of passive and active reflectors. Such reflectors are needed in all cases where a sufficient response from the ground is not available. In particular, the paper describes the development of a low-cost active reflector. This development was carried out in an EU H2020 project called GIMS. The paper summarizes the key characteristics of the developed active reflector. The reflector was tested in two main experiments: the first one located in the campus of CTTC and the second one in a GIMS test site located in Slovenia. The experiments demonstrate the visibility of the active reflectors and provide the first results concerning the phase stability of such devices.

The future 5G networks are expected to use millimeter wave (mmWave) frequency bands to take advantage of the large unused spectrum. However, due to the high path loss at mmWave frequencies, coverage of mmWave signals can get severely reduced, especially for non-line-of-sight (NLOS) scenarios as mmWave signals are severely attenuated when going through obstructions. In this work, we study the use of passive metallic reflectors of different shapes/sizes to improve 28 GHz mmWave signal coverage for both indoor and outdoor NLOS scenarios. We quantify the gains that can be achieved in the link quality with metallic reflectors using measurements, analytical expressions, and ray tracing simulations. In particular, we provide an analytical model for the end-to-end received power in an NLOS scenario using reflectors of different shapes and sizes. For a given size of the flat metallic sheet reflector approaching to the size of the incident beam, we show that the reflected received power for the NLOS link is the same as line-of-sight (LOS) free space received power of the same link distance. Extensive results are provided to study the impact of environmental features and reflector characteristics on NLOS link quality.

The need to minimize bycatch of toothed whales (odontocetes) in gillnets has long been recognized, because they are often top predators and thus essential to ecosystem resilience. It is likely that a key to achieving this goal is the improvement of gillnet acoustic visibility, because these species use underwater sonar for orientation. Previous work on increasing gillnet detectability for echolocating animals by making the nets more recognizable has been based on trial and error, without understanding the fundamental acoustic properties of the tested modifications. Consequently, these studies have produced mixed and sometimes contradictory results. We systematically identified small, passive reflective objects that can improve the visibility of gillnets at a broad range of frequencies, i.e., for many odontocetes. We simulated the acoustic reflectivity of a wide range of materials in different shapes, sizes, and environmental conditions, with a focus on polymer materials. We verified the simulation results experimentally and calculated detection distances of the selected modifications. For example, if 8 mm acrylic glass spheres are attached to the net at intervals smaller than 0.5 m, the spheres have the same target strength (TS) at 130 kHz as the most recognizable part of a gillnet, the floatline. Modifications of the netting material itself, e.g., using barium sulfate additives, do not substantially increase the acoustic reflectivity of the net.

The article reviews the problem of landing on hard-to-reach and poorly developed territories, especially in the case of unmanned aerial vehicles. Various landing systems and approaches are analyzed, and their key advantages and disadvantages are summarized; afterwards, an approach with passive reflectors is considered. A formal definition is provided for the main factors relative to the accuracy analysis, and a model is presented. The way to improve the landing procedure, while simultaneously meeting various practical constraints, is analyzed; the results of numerical simulation are presented, followed by the detailed conclusion describing still remaining challenges and subjects for further research.

This paper presents the scheme of a software planing tool for single microcells of broadband radio access systems operating at millimeter waves, providing local multipoint distribution services (LMDS), particularly in urban or suburban areas. The aim of this planing tool is to provide operators with information, which supports the assessment of the profitability by calculating link budgets and the area coverage and by roughly estimating the maximum number of potential customers, i.e. the total number of households in a~certain area, as well as the number of customers (households) which will actually be covered from a site. A household is here considered as a single apartment or flat, thus a building usually consists of several households. This novel household-estimation model is able to estimate the number of households based only on the 3D-data of buildings, without using residential data. Besides the optimization of line-of-sight (LOS) coverage, also the possibility is considered to enhance the coverage into shadowed areas by using optimized reflectors as passive repeaters up to distances of 1 km from the base station, depending on the system margin and the rain climate zone. All calculations are based on 3D-databases of both, buildings and vegetation.

The use of radar in automotive applications such as adaptive cruise control is limited to detecting target vehicles directly in front of the host vehicle. Vehicles around a curve on a highway and cross-traffic vehicles at an intersection cannot be detected by current radar systems. This is primarily due to the limited beam width angle of the radar. This paper examines and evaluates the novel concept of using passive roadside reflectors (PRRs) to increase the utility of the radar system. PRRs on the shoulder and the median of a road are designed which would enable the radar system to pick up cross traffic at highway intersections. Both simulations and experiments demonstrate that this concept could be effectively used for cross-traffic distance measurement. A limitation of this technology is that cross traffic cannot be detected when the radar-equipped vehicle is close to the intersection, owing to the lateral offset of the radar from the location of the PRR. However, the system is still valuable for providing future warning of cross traffic at rural intersections. A number of options are explored for the use of PRRs to improve radar measurements on highway curves. These include the use of tangential flat-plate reflectors, skewed flat-plate reflectors, and convex reflectors. Algorithms for distance measurement with each of these options are derived and evaluated through simulations. The use of skewed flat-plate reflectors is also evaluated experimentally and found to work effectively. The effective range of the radar on highway curves could be doubled by the use of the developed system. [ABSTRACT FROM AUTHOR]