Characterisation of the effects of thin radomes on antennas for space applications

For aperture type antennas in space applications, a thin radome in the mouth of the antenna is often employed. This radome is typically constructed of a layer of dielectric with a coating of paint on the exterior surface. Usually, the dielectric and paint can be made to be very thin as compared to the free space wavelength, and thus one anticipates that (for reasonably low loss material) the effect of the radome on the far-field is negligibly small. One must consider the antenna and radome interactions to properly account for the effects of the radome since the radome is typically in the near-field of the antenna. When the full interactions are taken into consideration, the loss can be considerably larger than the loss predicted by a simple plane wave transmission loss. For applications like scatterometer systems where the gain level in extended angular range is critical, or in systems for which the G/T level must be predicted accurately, the net radome loss can be significant. This radome loss is studied for a specific antenna geometry. It is shown that the loss in peak gain due to a radome is noticeably larger than that predicted by a plane wave analysis.<>