Cecilia Cappellin

Application of the SWE-to-PWE antenna diagnostics technique to an offset reflector antenna

A new antenna diagnostics technique has been developed for the DTU-ESA Spherical Near-Field Antenna Test Facility, which is operated by the Technical University of Denmark (DTU) for the European Space Agency (ESA). The technique is based on the transformation of the spherical-wave expansion (SWE) of the radiated field, obtained from a spherical near-field measurement, to the plane-wave expansion (PWE). It allows an accurate reconstruction of the field in the extreme near-field region of the antenna under test (AUT), including the aperture field. The fundamental properties of the SWE-to-PWE transformation, as well as the influence of finite measurement accuracy, have been reported previously. We validate here the new antenna diagnostics technique through an experimental investigation of a commercially available offset reflector antenna, where a tilt of the feed horn and surface distortions were intentionally introduced. The effects of these errors were detected inthe antennas far-field pattern, and the accuracy and ability of the diagnostic technique to subsequently identify them were investigated. Real measurement data were employed for each test case.

On the Comparison of the Spherical Wave Expansion-to-Plane Wave Expansion and the Sources Reconstruction Method for Antenna Diangostics

A comparison between two recently developed methods for antenna diagnostics is presented. On one hand, the Spherical Wave Expansion-to-Plane Wave Expansion (SWE-PWE), based on the relationship between spherical and planar wave modes. On the other hand, the Sources Reconstruction Method (SRM), based on the application of the equivalence principle and the integral equations relating fields and sources. In order to compare the results provided by these methods, a reflector antenna has been measured and analyzed.

Advanced techniques for grating lobe reduction for large deployable mesh reflector antennas

Spaceborne deployable mesh reflectors are lightweight antennas made by a tensioned net supporting an RF reflecting mesh, which are deployed in orbit. The tensioned net is typically made by regular and periodic planar triangles that cause unwanted grating lobes in the pattern of the antenna. Here, we build on a recent study and propose an improved configuration using a so-called pentagonal arithmetic mesh of non-regular and non-periodic triangles and a shifted feed that modifies the reflector phase distribution and simultaneously provides excellent grating lobe reduction and lowered sidelobes. This configuration may pave the way for future space missions relying on large deployable mesh reflector antennas.