Electronically Agile beam Antennas are able to generate moving radiation patterns to perform Beam Forming and Beam Steering. Today, the design of such antennas is performed by the well-known Array Technique called AESA: Agile Electronically Scanned Array which presents some limitations. To overcome these limitations, a new approach is proposed in this paper called “ARMA” (Agile Radiating Matrix Antenna). This approach defines Agile Beam Radiating Surfaces that are sampled using rectangular functions instead of Dirac combs for the arrays. The intrinsic advantages are demonstrated and the ARMA-AESA comparison shows a larger accuracy of ARMA approach, which overcomes the limitations inherent in the array technique.

Cost-efficiency, environmental sustainability, and dimension reduction are important aspects in wideband antenna design. Geopolymers could be an eco-friendly and cost-efficient solution for this application. The objective of this work is to develop new geopolymer-based composites with tailored dielectric properties for applications in radar antennas. For this, different formulations based on three metakaolin and two alkaline solutions were tested. The influence of magnetite was studied by insertion of 1, 5 or 10 ​wt % of Fe3O4 in different formulations. Furthermore, the influence of humidity was also emphasized. Dielectric investigations between 2 and 3.3 ​GHz were performed. The results showed that the metakaolin type had no effect on the dielectric characteristics, whereas the nature of activation alkaline solution had a significant influence. Indeed, an increase in permittivity from 3.5 to 5.9 is evidenced by the change in the alkaline solution. The addition of magnetite up to 10 ​wt % had a little influence on the polycondensation reaction and lead to a slight increase in permittivity and permeability values. Furthermore, the permittivity and the loss tangent increase at high relative humidity level, but the phenomenon is reversible. It was also demonstrated that time had no effect on the permittivity values.

An original monostatic UWB FMCW radar architecture has been developed for GPR applications. The radiation system is composed of a single antenna associated with a double switching configuration to minimize the compactness of the antenna system while ensuring a sufficient dynamic range. Moreover, an analog correction technique has been developed to linearize a low-cost free-running UWB Voltage Controlled Oscillator (VCO) and to enable operating frequency selection. A functional demonstrator has been designed and associated measurements are proposed.

UAV-mounted GPR are a very attractive way to detect buried objects without ground contact. However, to be efficient, conventional GPR systems use a large bandwidth turned towards low frequencies for better penetration into the ground, the objective of this paper is to discuss possible solutions to reduce the system size and weight in the 0.3-1GHz frequency band by using single switched antenna. The proposed choices are supported by a complete simulation of the RF chain performed using gprMax and Advanced Design System.

In this paper, we present a new design of optoelectronic system for transient shaping with a selection of rejected frequencies. The generation of short pulses is performed by several optoelectronic devices triggered via a laser flash. Photoconductive Semiconductor Switches (PCSS) operating in linear switching mode have been used. By using the appropriate number of optoelectronic generators, we create a spectrum ranging from 300MHz to 3GHz, with rejected frequencies at 900MHz and 1.8GHz.

In this paper, a guidelines for designing a volumetric ultra-wideband (UWB) antenna is proposed. The methodology is applied for the design of various travelling waves antenna shapes. A comparative study between various design geometries leads to a particularly interesting antenna dimensions: The K antenna. We demonstrate the use of an appropriate dielectric material is an efficient way to reduce the antenna dimensions. Furthermore, the behavior of an antenna filled with resin intended for Ground Penetrating Radar is validated using the experimental results.

A cylindrical near field antenna measurement facility working in the time domain and combining Near Field to Far Field transformation is presented. A transient impulses generator of 3 GHz bandwidth is used as antenna feeder. The received signal is measured in time domain by an UWB sensor connected to a real time oscilloscope. Because this setup is based on outdoor measurement, it offers significant yields in installation and material cost.

The originality of the radiation source presented here is localized in its ultrafast speed and its autonomy of scanning a large spatial area. That behavior is obtained by means of a trigger mode of radiation perfectly controlled by a single optical source. The transmitter consists of a powerful picoseconds laser, an optical power divider and n optoelectronic ultra-wideband radiation sources which produce several electric pulse trains with a repetition rate slightly different one with each other. Each train is then addressed toward a single antenna. When transmitted the electromagnetic waves interact to produce an ultrafast orientation of the array emission lobe allowing scanning of large spatial field in less than 1μs.

Many studies were devoted to the analysis and the detection of electromagnetic attacks against critical electronic systems at the system or the component levels. Some attempts have been made to correlate effects scenarios with events logged by the kernel of the operating system (OS) of commercial-off-the-shelf computer running Windows. Due to the closed principle of the last OS, we decided to perform such an analysis on a computer running a Linux distribution in which a complete access to logs is available. It will be demonstrated that a computer running such an open OS allows detecting the perturbations induced by intentional electromagnetic interferences at different levels of the targeted computer.

Optoelectronic devices triggered by a laser flash and operating in linear switching regime, allow the generation of short pulses with small time jitters (2ps typically). An Ultra Wide Band antenna array combining as many of this photoswitches as antennas has the advantage to increase the radiation power on one hand and to offer the agility of the radiation beam on the other hand obtained by time delay of laser illumination. The increase of the peak power and the frequency band can be obtained by integrating the photoswitch in the antenna. An equivalent model of photoswitch can be created with the transient solver of CST Microwave Studio coupled within CST Design Studio. This article presents the integration of a photoswitch within the antenna and the improvement of radiation.

Summary form only given. Ultra Wide Band (UWB) antenna arrays offer the possibility to generate a wide band signal in a sharp direction, which can drastically improve the detection sensitivity. With a configuration including as many antennas as generators, an UWB array presents the advantage of increasing the radiation power on one hand and offering the agility to the array on the other hand. Indeed, the application of time delays between the feeding pulses of the antennas permits to steer the radiated fields in each wanted direction and to realize a coherent sum of each initial power.

A novel method allowing the ultrafast scanning of an area thanks to an Ultra Wide Band (UWB) antenna array is proposed in this paper. This method is based on the use of asynchronous optical pulses trains with difierent repetition rates obtained in amplifled regenerative cavities. By means of optoelectronic switching, providing short powerful electrical pulses trains to an UWB antenna array, it is possible to spatially scan a large area in less than 1ms. The paper presents the principle of the transient beam steering and its potentialities to realize an ultrafast detection system.

This letter describes an innovative method of characterization of rubble on the frequency band [300MHz–3GHz]. Some simulations and measurements have been done to deduce the electromagnetic behavior through the rubble with specific dielectric properties and different configurations. The key of our characterizations method are presented, measurement and simulation results are illustrated and discussed.

This paper shows the development of a new measurement range working outdoor in Near-Field time-domain, and used to characterize ultra-wide band as well as narrow band antennas.

This paper proposes two studies on a Shark antenna array, working in the frequency band [800MHz - 8GHz], in a configuration including N generators and N antennas. The first study deals with the evaluation of the performances of the array from the analyze of the transient performances of the elementary system "generator + antenna". The second study concerns the comparison of two arrays having the same surface area, but a different number of antennas thanks to a scaling method on the dimensions of the elementary antenna.

The conception of a novel Ultra-Wideband (UWB) antenna array, designed especially for transient radar applications through the frequency band (300 MHz–3 GHz), is proposed in this paper. For these applications, the elementary antenna must be compact and nondispersive, and the array must be able to steer in two dimensions. The geometry of the elementary antenna and its radiation characteristics are presented. The array beam steering is analyzed and a technique making the increase of the transient front-to-back ratio possible is described.

This paper describes the outdoor transient measurement base using cylindrical coordinates system. This measurement base will be used for antenna's characterization, particularly in the determination of the electric far field of any type of radiating source.

This paper is dedicated to an original miniature antenna for transient Ultra Wide Band applications : the Shark antenna. This antenna is well matched from 800MHz up to 8GHz, has a sectoral transient radiation pattern, has a high transient front to back ratio, and is dedicated to be used in an array with an N generators / N antennas architecture. This paper presents the design and the characteristics of this antenna.

This paper aims at presenting the design and realisation of an autonomous, ultra wideband (UWB) radiation source consisting of a high gain broadband antenna driven by a subnanosecond pulsed power source.The high voltage pulse source is a single ten stage subnanosecond Marx generator which delivers pulses in the range of 250kV/1.5J, with a minimum 300ps rise-time, subnanosecond pulse duration at a maximum pulse repetition frequency of 350Hz. The main particularity of our system is to integrate the pulse forming device (a peaking stage and a crowbar switch), directly on the last stage of the Marx generator. This adjustment avoids the loss of output pulse amplitude due to a classical pulse forming line. The development of the Marx generator combined with its own pulse forming device is explained and discussed in the paper.Dedicated home made probes based on capacitive line divider are realized to measure both the temporal characteristics and the high voltage amplitude of the pulses delivered by the pulsed power source. These probes allow to observe voltage pulses without perturbation in any place of the circuit and to measure their main characteristics. Its 2.3GHz high cut off frequency and its sufficient division ratio permits to measure the rise-time, fall-time, pulse width and the amplitude of the output signal of the pulser. Calibration tests in the frequency and time domain are also performed and detailed in the paper.Another major factor in UWB radiation systems is the radiating element. The pulsed source is combined with a travelling wave antenna called Valentine antenna. Some mechanical modifications were made to improve the dielectric strength of this radiating element. A 3-D model of its structure, on a time domain electromagnetic software, was first performed to study the influence of these modifications on the main radiating characteristics of the antenna. Then, this antenna is tested with HV pulses in order to avoid any undesirable breakdown.Various tests on the whole source (battery-DC/DC converter-Marx generator-pulse forming device-antenna) were investigated in order to evaluate the figure-of-merit of our system. A novel method to measure high level electromagnetic fields, called MICHELSON method, is used. The incident field scattering on a target permits to move the field measurement toward a novel location, where a simple equipment can measure the scattered field without breakdown risk. The results obtained with this method are compared to ones measured with a classical derivative field sensor. Moreover, the high gain and capability of the Valentine antenna to radiate short pulses without dispersion allow achieving a high measured figure-of-merit. Finally in this paper, the maximum figure-of-merit obtained is 450kV with our compact source.