Laurent Desrumaux

An Original Antenna for Transient High Power UWB Arrays: The Shark Antenna

A novel ultrawideband (UWB) antenna, called the Shark antenna, and designed especially for transient applications is proposed in this paper. A Shark antenna array is also conceived in order to obtain a high power UWB pulse radiation source through the frequency band [800 MHz-8 GHz]. For this application, the elementary antenna must be compact, non-dispersive, and the array must have a high transient front to back ratio. The geometry of the Shark antenna and its radiation characteristics are detailed. Moreover, an approach which evaluates the transient front to back ratio of a square array is presented.

A Transient UWB Antenna Array Used with Complex Impedance Surfaces

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.

AN INNOVATIVE RADAR IMAGING SYSTEM BASED ON THE CAPABILITY OF AN UWB ARRAY TO STEER SUCCESSIVELY IN DIFFERENT DIRECTIONS

An innovative radar imaging system, based on the capability of a flxed UWB array to radiate short pulses in difierent directions along time with the principle of electronic beam steering, is presented in this paper. To demonstrate its concept, the analysis presented in this paper is based on simulation results. As function of the use of either only one antenna or several antennas in reception, two radar imaging algorithms have been developed and are detailed in this paper. These algorithms permit to obtain an image of the analyzed scene thanks to the transient beam pattern of the array used in emission. Finally, with a same analyzed scene, these algorithms have been compared with the time reversal method and the back projection algorithm, in association with a SAR imaging system. The conditions of applicability of these methods are also discussed.

A pulsed power source to drive an innovative autonomous scanning UWB radiation system

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. However, a major difficulty with such a configuration is the minimization of the radiation source jitters, to obtain the best synchronization possible. A solution consists of using pulsed optoelectronic devices, operating in linear switching regime, which permits to bypass this difficulty and to obtain ultra-short electrical waveforms with small temporal jitters (2ps typically). Many applications such as transient radar cross section (RCS) measurements, UWB synthetic aperture radar (SAR) and high power UWB radiation source can be developed by using such systems. In this paper, the design of an innovative autonomous scanning radiation system will be approached. The first experimental results will be also presented. These results are essentially focused on the high voltage pulsed power source which is previously described. This source aims at driving the pulsed optoelectronic devices. It consists of a series-connected IGBTs component.

UWB impulse radiation source with integrated optoelectronic generator

The study presented in this article belongs within the context of a design of a new kind of short-range Ultra Wide-Band (UWB) Radar with an autonomous scanning capability. The generation of short pulses is performed with an optoelectronic device triggered by a laser flash and operating in linear switching mode. By adding as many optical systems as antennas, we create a transmitting array with increased radiated energy. Each of those elements are fed with bursts composed of UWB optogenerated pulses with a slightly different pulse repetition frequency allowing beam-scanning capability. This article presents in detail all the parts needed to implement the elementary radiation source and offers a mathematical method of calculation to trace back to the generated feeding signal.

ULTRAFAST AUTONOMOUS DETECTION AND SCANNING SYSTEM BASED ON OPTOELECTRONIC PULSE SWITCHING

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.