An oil peaking switch to drive a dipole antenna for wideband applications

When the load is an antenna, the High Pulsed Power (HPP) generators allow generating electromagnetic waves in the form of pulses for wideband or ultra wideband applications. In this case, the HPP generator is usually made up of a primary energy source loading a power-amplification system. A Marx generator or a Tesla transformer is classically used as a power-amplifier. Our structure uses an innovating very compact resonant transformer. This power amplification device is connected to a fast switch which forwards the energy from this source to the antenna. The antenna behavior is directly linked to the performances of the main element of this whole device: an oil peaking switch. The whole device is composed of a battery set, a DC/DC 300V-10kV converter which feeds four primary capacitors with a 1.2A current, four triggered spark gap switches, a resonant transformer with four primaries generating a few hundreds kV pulses, the oil peaking switch and the dipole antenna. The device must transmit waveforms with a wide frequency band. This paper presents first the preliminary studies on an oil switch used in a transmission line setup. Several oils are studied, tested and compared. First experimental tests aimed at determining the electrical breakdown field in oils and the rise-time for conditions close to our application. The switch characteristics (breakdown voltage, breakdown electric field, rise time, etc) are thus studied for various electrodes gap distances. These results and the influence of these previous parameters on the antenna performances (antenna factor, figure-of-merit, radiated field) are predicted by CST Microwave Studio and compared to measurements.