An Electrically Small Conical Folded Dipole Antenna for Use as a Compact, Self-Resonant Mesoband High-Power Microwave Source

Mesoband (MB) high-power microwave (HPM) sources use fast-risetime switches to trigger weak resonators in order to create a damped sinusoidal waveform. MB sources are more compact and less complicated than narrowband HPM sources, and they possess increased energy spectral density per pulse relative to ultrawideband HPM sources. In this paper we consider the design of a MB HPM system that operates at the low end of the VHF spectrum (below 50 MHz) that is based on a self-resonant, electrically small antenna (ESA). The ESA is based on a conical folded helix design. It is slowly charged up to high voltage, and it is then switched using a fast-rise time switch to convert the stored static energy into radiated electromagnetic fields. Here we show the design, modeling, and preliminary experimental results of the source operating as low as 38 MHz at an electrical size of ka = 0.43, where a is the radius of a sphere circumscribing the source. Experimental results are obtained in the far field for a charge voltage of 30 kV.