The GIMLI: A Compact High-Power UWB Radiation Source

Abstract

This chapter presents the design and performances of a compact, general-purpose, high-power ultra-wideband (UWB) source named GIMLI. The system was designed for dual use, homeland security and military applications. It is powered by a compact, coaxial 12-stage Marx generator with a rise time lower than 25 ns and an operating voltage up to 360 kV. A fast monocycle pulse is sharpened using a pulse former (MPF). The shaper stage comprises a switching module including a peaking and a grounding multi-channel spark gap under a N₂ pressure of 6 MPa. The module is followed by a monopulse-to-monocycle converter based on a coaxial Blumlein pulse forming line. The bipolar signal measured at the output of the MPF has a duration shorter than 2 ns with a rise time of 250 ps. The peak-to-peak output voltage is 250 kV on a 50 Ω resistive load. Repetitive operation of the MPF has been experienced with a 200 Hz Tesla transformer developed by the CEA (Commissariat à l’Energie Atomique). Electromagnetic energy is focused by a dedicated antenna. The designed antenna is a TEM half-horn with two ridges which improve the low-frequency focusing. High-power radiation tests show that the field measured at a distance of 9 m from the TEM Horn-antenna is higher than 120 kV/m.