Design of high PRF ferrite-loaded pulse sharpening devices

Ultrawideband radar (UWB) systems require a pulse generator to drive the antenna. The required pulse repetition frequency (PRF) for UWB systems is typically 1-30 kHz. Pulse generators with thyratron or FET switching can meet the PRF requirement, but develop relatively slow output rise-times of 2-20ns. One approach is to combine such a high PRF pulse generator with a pulse-sharpening device. The Cardiff University group has produced a design of ferrite-loaded coaxial line pulse sharpener with a flowed water dielectric layer/coolant. The line is driven with a 10 kV, 2.5 ns input pulse at 0-30 kHz (or 60 kHz in burst mode), and produces a constant 8 kV, 150 ps rise-time output pulse. This order of PRF is thought to be a unique capability for any sub-ns rise-time, kV level pulser system. The structure of the line is outlined in comparison with a line based on small ferrites and a heatshrunk dielectric layer. The centre conductor contains a set of channels which provide an additional path for coolant flow. The centre conductor also provides mechanical support for the ferrite bead. The ferrite beads are a NiZn grade with high saturation (0.45 T) and low coercivity (50 A/m)