Experiments on Broadband EMP Radiation with an Axial Mode Helix Antenna

Abstract

To produce broadband electromagnetic pulse (EMP) radiation, we design and test a sub-ns pulse system which is utilized to drive an axial mode helix antenna. This sub-ns pulse system consists of a 10-stage Marx generator, an intermediate storage capacitor, an impedance transforming line, and can generate a high voltage of 570 kV with a rise time of 1-1.5 ns on a 300-Ω-resistance load. The diameter, pitch and turns of the helix antenna are 29 cm, 19.5 cm and 5, respectively, with a design frequency of 300 MHz. When the charging voltage of the Marx generator is 30 kV, the electric field of radiated EMP measured 3m from the source is 35 kV/m with a central frequency of 250 MHz. The relatively spectral bandwidth is 25%. The radiated EMP results are reproducible and the system will work in repetition mode if the available dc power is utilized.