Keywords:VHF antenna; ground penetrating radar; low frequency antennas; antenna pattern; Open Area Test Site (OATS); Europa Clipper; Jupiter; drone; far-field measurement
Publisher:Pasadena, CA: Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2018
Citation:2018 IEEE Symposium on Electromagnetic Compatibility, Signal & Power Integrity, Long Beach, California, July 30 - August 3, 2018
Abstract:
This paper presents measurements and simulations of a linearly polarized VHF folded dipole operating at 60 MHz for NASA’s upcoming Europa Clipper mission. The spacecraft contains a ground penetrating radar, consisting of an array of four VHF antennas, that will characterize the surface of Jupiter’s icy moon Europa. Measured far-field radiation patterns and reflection coefficients above a 50×80m perfect ground plane are compared to predicted results using commercial software. Normalized Far-Field radiation pattern cuts are measured utilizing a biconical antenna and receiver mounted on a flying drone. Simulations of the radiation pattern show that the number of lobes increases with the distance of the antenna from the ground due to the ground-bounce phenomenon. In addition, the measured and simulated reflection coefficients stay unchanged for height above 2 meters, which matches the predicted calculation of the reactive-near field region of this antenna. However, the antenna electrical parameters are optimized for use on the spacecraft and become detuned in the presence of a ground plane. Simulated and measured return loss discrepancy less than 0.5 dB is presented. Radiation pattern comparisons show similar agreement when taking into account the effect of far-field measurement uncertainties.