ELECTROMAGNETIC WAVES EXCITATION BY A UNIPOLAR HIGHVOLTAGE PULSE IN A FERRITE COAXIAL LINE WITH A PERIODIC METAL STRUCTURE

Experimental data and results of numerical simulations are presented, concerning excitation of narrowband gigahertz-range wave trains in coaxial guiding structures that are partially filled with ferromagnetic material and may involve periodically arranged metal inserts. The experiments performed confirm the possibility of exciting weakly damped electromagnetic waves by feeding high voltage, unilateral electromagnetic pulses of short duration into the line. The coax line was of outer diameter 50.5 mm, filled with an isotropic dielectric (relative dielectric constant ε = 2.25) and a set of ferrite rings with ε=16 and saturated-state μ about 4 to 5. With a peak voltage of the primary pulse close to 160 kV and a magnetizing field of 17.5 kA/m, the parameters of the waves excited reached magnitudes as: frequency 1.89 to 2.1 GHz; bandwidth 16%; VHF power at the output about 20 MW.