Antenna gain can be measured in a multipath site by moving the antenna under test away from the probe antenna at different distances, and by assessing a normalized transfer function as an average figure over the entire data set. In an earlier work, we provided a statistical explanation to the reduction of the multipath effects. Another possible explanation is based on the synthetic aperture principle, by assimilating the positions of the probe antenna to an antenna array. In this paper, we compare linear scanning to matrix scanning in order to draw optimal choice criteria for the grid of measuring positions. Measurements were performed on a Vivaldi antenna.
As shown in another paper , we have imagined and built radio modules for path loss models calibration, to be integrated on autonomous robotic platforms or drones . 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.
This paper aims to present a calibration optimization method for radar cross section measurement setup using time domain measurements. The proposed method requires a measurement of S21 parameter of a metallic plate with a known RCS at 13 different distances. A post processing technique reveals the correlations between the distances of measurements and time domain representations of S21 extracted parameter. Time-domain representation of S21 also depends on the wave propagation time on the antenna (Vivaldi and log-periodic) feeding line which inserts a delay. Time domain perspective clearly provides propagation delay data on antennas which are almost undetectable in frequency field. The principles of this method are provided together with experimental and simulation validations. At a distance of 22cm between antennas, mutual coupling influence affects every measurement set and is being reduced in post processing. This method also provides the impulse response of the whole measurement setup.
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  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.
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.
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.
The log-normal propagation model is usually applied for scenarios including a line-of-sight path. However, there are many
cases that do not include such a propagation path, e.g. indoor transmission and disaster situations, when radio waves have
to penetrate trough ruins. In this paper, we show that the log-normal model can also be applied for non line-of-sight
transmission. Both indoor scenario and trough-ruins scenario, are investigated.
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.
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).
In this paper, we propose an approach of optimization of meander line antennas by using genetic algorithm. Such antennas are used in RFID applications. As opposed to other approaches for meander antennas, we propose the use of only two optimization objectives, i.e. gain and size. As an example, we have optimized a single meander dipole antenna, resonating at 869 MHz.
In this paper we present a type of antipodal Vivaldi antenna design, which can be used for pulse radiation in UWB communication. The Vivaldi antenna is a special tapered slot antenna with planar structure which is easily to be integrated with transmitting elements and receiving elements to form a compact structure. When the permittivity is very large, the wavelength of slot mode is so short that the electromagnetic fields concentrate in the slot to form an effective and balanced transmission line. Due to its simple structure and small size the Vivaldi antennas are one of the most popular designs used in UWB applications. However, for a two-antenna radar system, there is a high mutual coupling between two such antennas due to open configuration. In this paper, we propose a new method for reducing this effect. The method was validated by simulating a system of two Vivaldi antennas in front of a standard target.