This paper presents an experimental wireless sensor network for monitoring underwater acoustic noises. Each sensor node consists of a floating platform anchored in the location of interest, powered by solar panel and storing excess electricity in Li-Ion batteries for uninterrupted operation. The communication between the sensor nodes and the central node (gateway) will be made by a radio link operating with the LoRa standard on the frequency of 433 MHz, a link that allows minimizing consumption and maximizing the distance between the sensor nodes and the central node (several km). The network implements the star topology. The sensors continuously monitor the sounds in the underwater environment and are triggered to store 5s of noise and then send it over the radio link to the gateway where it is stored locally on a server or sent to the cloud, in a database for further processing. The trigger level is configurable. Sound acquisition can also be started on demand, remotely.
This paper presents an experimental implementation of ground-based interferometric synthetic aperture radar based on the low cost USRP platform and a computer. The purpose of the proposed system is to measure small displacements of the monitored targets over a long time period. These types of measurements are particularly useful in the field of civil engineering and ecology. Common applications are landslide monitoring or bridge and building deformation analysis, as well as glacier movement monitoring. The system implements stepped-frequency radar operation with a maximum bandwidth of 1500 MHz (500 – 2000 MHz). As expected with all interferometric measurements, due to the cyclic nature of the phase shift, the displacement must be smaller than a certain fraction of the wavelength of operation; otherwise the result will be ambiguous. In our case the displacement must be smaller (in absolute value) than a quarter of the transmitted wavelength. Due to the fact that in a software-defined radio the frequency is user selectable in a very wide range, the system can be configured to adapt to the magnitude of the expected displacement.
An experimental implementation for a low-cost, software-defined Ground Penetrating Radar is presented in this paper. The proposed system uses a general purpose low-cost SDR platform with minimal external components. The SDR platform is USRP N200 equipped with WBX RF daughterboard. The only external additions are two off-the-shelf RF switches, an Arduino Uno microcontroller board, a fixed RF attenuator and two Vivaldi antennas. The system implements stepped-frequency radar operation with a bandwidth of 1500 MHz achieving a resolution of 10 cm in air. It works by sweeping this frequency band transmitting sine waves and storing the amplitudes and phases of the scattered waves. Then, this frequency-domain information is translated into time-domain by means of Inverse Fast Fourier Transform (IFFT). The time-domain responses are plotted in an A-scope image. Then, these images are combined to create the classic B-scope image used in ground penetrating radars. All of the above-mentioned assertions have been validated experimentally.
This paper presents a practical implementation of a software-defined ground-based synthetic aperture radar. The proposed system uses a PC, a general purpose low-cost SDR platform and a minimum number of external components. The SDR platform is a USRP N200 equipped with a WBX RF daughterboard. The only external components are two offthe- shelf RF switches, an Arduino Uno microcontroller board, a fixed RF attenuator and two Vivaldi antennas. The system implements stepped-frequency radar operation with a bandwidth of 1500 MHz (500 – 2000 MHz) achieving a resolution of 10 cm in air. The proposed system mimics the behavior of Vector Network Analyzers. It works by sweeping its operating frequency over the 1500 MHz frequency band and storing the amplitudes and phases of the scattered waves. These are assembled in a matrix, the so-called raw data matrix, which is processed using an implementation of the backprojection (BP) SAR algorithm to generate the bidimensional focused image. All of the above-mentioned assertions have been validated experimentally, proving the proposed system’s ability to generate high resolution images of the analyzed scene.
This paper presents an experimental implementation of continuous-wave interferometric radar based on low cost USRP platform and computer. The purpose of the proposed system is to measure small displacements of the monitored target over a long time period. These measurements are extremely useful in the field of civil engineering. Common applications are landslide monitoring or bridge and building deformation analysis. The proposed solution transmits a monochromatic radio wave towards the monitored target and measures the phase shift suffered by the reflected wave. The measured phase shift is stored in a file on the hard drive of the computer. After a certain period of time, spanning from minutes to years, specific to the application, with the system placed in the same position, a second phase shift measurement needs to be performed, storing a new result. The system then computes the difference between the two stored phase shifts and determines the displacement. As expected for all interferometric measurements, due to the cyclic nature of the phase shift, the displacement must be smaller than a certain fraction of the wavelength of operation; otherwise the result will be ambiguous. In our case the displacement must be smaller (in module) than a quarter of the transmitted wavelength. Due to the fact that in a software-defined radio the frequency is user selectable in a very wide range, the system can be configured to adapt to the magnitude of the expected displacement. All of the above-mentioned assertions have been validated experimentally.
This paper presents a practical implementation for low-cost, software-defined Ground Penetrating Radar. The proposed system uses solely a general purpose low-cost SDR platform, two antennas and a PC. The main advantage of this implementation compared to similar implementations in the literature is the absence of external components/circuits or custom-built RF boards. The SDR platform is USRP N200 equipped with WBX RF daughterboard. The only external additions are two Vivaldi antennas. The system implements chirp radar operation with a bandwidth of 40 MHz achieving a theoretical resolution of 375 cm in air. Because of the reduction of electromagnetic wave velocity in soil, the resolution improves significantly in practical situations where the wave travels through a high permittivity medium. The resulting system is capable to successfully discover large subterranean voids like caves or tunnels. The paper presents an experimental validation where the proposed system is employed to detect the presence of a tunnel.
Underwater digital communication and sonars rely on basic signal detection. The problem with underwater signal detection is that of the extremely expensive equipments. In this paper we propose both a low cost solution for signal detection, which practically consists in integrating and adapting the already existing equipments and methods for underwater noise analysis.
As shown in another paper [1], we have imagined and built radio modules for path loss models calibration, to be integrated on autonomous robotic platforms or drones [2]. Path loss models are very useful in disaster situations, helping to locate radio signal sources such as mobile phones, buried under collapsed buildings as a result of earthquakes, natural disasters, terrorism, war, etc.
KEYWORDS: Transceivers, Receivers, Analog electronics, Integrated circuits, Data modeling, Calibration, Signal detection, Amplifiers, Electronics, Robotics
For search and rescue scenarios [1,2], radio devices with precision comparable to laboratory instruments are needed. More than that, the modules have to be small enough to be integrated on autonomous robotic platforms [3] or drones, for search and rescue activities. Power consumption have to be small enough to sustain a reasonable time of autonomy. For this purpose, we have imagined two modules, a fixed frequency receiver and a wideband transceiver.
The paper is an exploratory research regarding the identification of some of the basic ideas used to conceive solutions of general-defined problems. In this way, there is firstly presented the set of ideas used to choose the type of model to be developed. The general problem solver and the related problems are also presented in the paper. In this case there is used a greedy approach which may lead to large run time values of the according software. To significantly decrease the computer time used to solve such a problem, there is also presented a method used to minimize the search space of the candidate solutions, in this case being used an intelligent solver, that is more effective than the greedy method. Two examples of models based on the previously presented general directions are also given. The first example presents an algorithm used to solve an equilibrium problem in ship strength problems. The second example is in electronic engineering. The ideas presented in the paper are important to identify the concepts employed to design modeling strategies and also for the development of the original software instruments structured as reusable libraries.
This work provides an experimental implementation of the cognitive software-defined Doppler radar based on the low cost USRP platform developed by Ettus Research. The proposed solution employs spectrum sensing in order to take advantage of the white spaces of the radio spectrum. The system continuously adapts its operating frequency according to environment changes, reducing the risk of interfering with other radio systems and acquiring a higher degree of immunity against jamming. The novelty of the proposed algorithm used for dynamically allocating the system’s operating frequency lies in its ability of covering a wide frequency bandwidth despite of the reduced instantaneous bandwidth of the low cost USRP platform employed in the experimental setup. Another related advantage of the proposed algorithm is the reduced computational power required for the real-time operation of the system. All of the above mentioned assertions have been validated experimentally.
In this paper we propose a new method for detection and localization of electric arcs by using two ultra-wide band (UWB) antennas together with data processing in the time-domain. The source of electric arcs is localized by computing an average on the inter-correlation functions of the signals received on two channels. By calculating the path length difference to the antennas, the direction of the electric arcs is then found. The novelty of the method consists in the spatial averaging in order to reduce the incertitude caused by the finite sampling rate.
Antenna gain is usually evaluated under far-field conditions. Furthermore, Friis transmission formula can solely be applied when antenna size can be neglected with respect to the distance between the measuring antenna and the antenna under test. In this paper, we show that by applying the distance averaging technique the far-field and antenna size constraints can be overcome. Our method was validated by measuring a monopole antenna and a Vivaldi antenna in an open area test site (OATS).
KEYWORDS: Robotics, Radio propagation, Buildings, Data modeling, Robotics, Data acquisition, Receivers, Non-line-of-sight propagation, Environmental sensing, Global Positioning System, Mobile devices
This paper deals with the use of autonomous robotic platforms able to locate radio signal sources such as mobile phones, buried under collapsed buildings as a result of earthquakes, natural disasters, terrorism, war, etc. This technique relies on averaging position data resulting from a propagation model implemented on the platform and the data acquired by robotic platforms at the disaster site. That allows us to calculate the approximate position of radio sources buried under the rubble. Based on measurements, a radio map of the disaster site is made, very useful for locating victims and for guiding specific rubble lifting machinery, by assuming that there is a victim next to a mobile device detected by the robotic platform; by knowing the approximate position, the lifting machinery does not risk to further hurt the victims. Moreover, by knowing the positions of the victims, the reaction time is decreased, and the chances of survival for the victims buried under the rubble, are obviously increased.
This paper presents an application of antenna arrays and MUSIC algorithm for estimating the location of an electric arc source. The proposed technique can be used to localize arc faults in photovoltaic arrays and their associated transformation stations. The technique was implemented and tested in the laboratory. For this purpose, an experimental setup consisting of 4 antennas, a digital storage oscilloscope with computer connectivity and a PC (Personal Computer) for data processing was built. The results proved that the proposed method is able to estimate the direction of the electric arc source with reasonable accuracy.
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