Conformal VHF Log-Periodic Balloon Antenna

A conformal log-periodic balloon antenna operating at a very high-frequency (VHF) band is presented in this communication. The antenna consists of eight conformal bowtie-dipole elements cross-fed by a parallel-strip transmission line and is then attached to the surface of a cylindrical balloon. After a detailed comparative analysis of the radiation performance of conformal strip dipole and bowtie dipole, a conformal log-periodic bowtie-dipole balloon antenna is designed. Simulated results show that its operating bandwidth ranges from 60 to 233 MHz with the voltage standing wave ratio (VSWR) less than 2 and a good end-fire radiation pattern of 5-dBi average gain. Measured results of a full-scale prototype fabricated with aluminum foils and a polyvinyl chloride balloon are in good agreement with simulated ones, which demonstrates the balloon antenna's potential applications in VHF communication systems.