We propose a novel ultrawideband (UWB) antenna designed specially for transient UWB radar applications. This work is a part of a new project concerning an optoelectronic UWB radar demonstrator with an array of four antennas. This project required the development of a new UWB antenna: the Valentine antenna. This antenna must be lighter and more compact in H-plane to allow the assembly of the array. This array must have a volume lower than 1 m . This antenna, which is composed of curved metallic strips, radiates ultrashort pulses in the frequency band 300 MHz -3 GHz with very low dispersion, a high gain and a low cross-polarization in the axial direction. The Valentine antenna must support 10 kV of peak voltage. This paper describes the Valentine antenna and its main radiation characteristics.
Systems emitting ultra-wideband high power microwave (HP/UWB) pulses are developed for military and civilian applications. HP/UWB pulses typically have durations on the order of nanoseconds, rise times of picoseconds and amplitudes around 100 kV m(-1). This article reviews current research on biological effects from HP/UWB exposure. The different references were classified according to endpoints (cardiovascular system, central nervous system, behavior, genotoxicity, teratology …). The article also reviews the aspects of mechanisms of interactions and tissue damage as well as the numerical work that has been done for studying HP/UWB pulse propagation and pulse energy deposition inside biological tissues. The mechanisms proposed are the molecular conformation change, the modification of chemical reaction rates, membrane excitation and breakdown and direct electrical forces on cells or cell constituents, and the energy deposition. As regards the penetration of biological matter and the deposited energy, mainly computations were published. They have shown that the EM field inside the biological matter is strongly modified compared to the incident EM field and that the energy absorption for HP/UWB pulses occurs in the same way as for continuous waves. However, the energy carried by a HP/UWB pulse is very low and the deposited energy is low. The number of published studies dealing with the biological effects is small and only a few pointed out slight effects. It should be further noted that the animal populations used in the studies were not always large, the statistical analyses not always relevant and the teams involved in this research rather limited in number.
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