Compact antenna concepts for mesoband HPM applications

High power microwave (HPM) systems often suffer from being large in volume and mass. Specifically the antennas for HPM systems tend to be very large, as the field levels must be kept below what is required for holdoff in air. The general utility of HPM systems could is enhanced when they are made low profile, increasing the number of platforms and applications for which they can be considered. In this paper we present our modeling and experimental work on electrically small antennas for HPM (or more appropriately HPEM, since we are working below the microwave band). We consider two concepts: a modified biconical helix antenna for use at frequencies below 50 MHz and an adapted magnetic EZ antenna for use in the UHF (500 MHz). In both cases, demonstrated performance at small sizes between ka = 0.4 and 0.5 is realized.