Feasibility Study of Parabolic Reflector for Structured Radio Waves SAR in Small Satellites

The needs for disaster monitoring, infrastructure management, and climate change mitigation have motivated fast-paced advances in earth observation technologies. One example is the use of structured radio waves in synthetic aperture radar (SAR) technologies. These structured radio waves, including vortex electromagnetic waves that carry orbital angular momentum (OAM), are radio wave fields that can be arbitrarily controlled across all degrees of freedom, from spatial to temporal. By implementing these technologies on small satellites, the amount of information that can be gathered has the potential to dramatically increase. However, there are some challenges for practical use in earth observation; one major challenge is energy dissipation. We investigated the extent of the energy dissipation in the structured radio waves at X-band frequencies, and then, we estimated the diameter of a parabolic antenna and the noise equivalent sigma zero (NESZ) required for the structured radio waves SAR in small satellites. The results indicated that the small satellite, equipped with a 5-meter diameter parabolic reflector and an NESZ set to −15 dB, can accommodate up to a 20 dB gain reduction (approximately up to Mode 1 or 2) in the structured radio waves. Additionally, we confirmed the generation of structured radio waves using a parabolic antenna with a uniform circular array (UCA) as feeder.