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This paper presents some recent developments in multiple beam antennas (MBAs) based on reflectarrays for communication satellites in K-and Ka-bands. The existing high throughput satellites commonly employ four reflector antennas to provide cellular coverage formed by multiple spot beams in a four color scheme. Reflectarray antennas are proposed as an attractive solution for the design of novel MBA configurations to produce multi-spot coverage with a smaller number of apertures than conventional MBA systems based on reflector technology. Single and dual reflectarray configurations have been considered for this purpose, exploiting the reflectarrays' ability to produce independent beams in different polarizations and frequencies.

Characterization of backscatter from complex or nonstationary targets, which is partially polarized, is considered first. The possibility of constructing the covariance matrix from coherency matrix measurements is investigated, and examples using practical polarization diversity radar data from meteorological targets are given. From examining the practical data, it is found that, for this type of target, reflection symmetry exists, thus giving indication about the physical properties of the medium. In particular, this shows that models, in which symmetrical distributions of both canting angle and shapes are assumed, are sufficient. Using the obtained matrix, propagation effects are examined under that assumption. Since the theory developed is amenable to implementation using a unique microwave circuit, results should have direct practical applications.

This contribution introduces a novel airborne system for subsurface sensing and imaging applications. The system consists of a Ground Penetrating Radar (GPR) mounted on an Unmanned Aerial Vehicle (UAV). Since the system does not need to be in contact with the soil, it is particularly useful for some Non-Destructive Testing (NDT) applications such as landmine detection or archeological surveys. An overview of the system and some of the first flight tests are shown in this contribution. The results of these flight tests prove the feasibility of the system to detect both metallic and dielectric targets. Furthermore, since the system includes a high-accuracy positioning system, measurements could be coherently combined to improve the radar image resolution.

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