Millimeter wave antenna for limb sounding application

The millimeter wave antenna study (MMWA) carried out under the ESTEC contract focused on antenna optimizations for a microwave limb sounding instrument for the middle atmosphere (10 to 100 km) which exploits four frequency bands, from 63 GHz for pressure retrieval up to 205 GHz for ozone. Six elliptical beams with ±0.3° scanning capability within the elevation plane were shown to be compliant with a tight beam efficiency specification of 96% inside the efficiency cone, defined by its apex angle to be 2.5 times the half-power beamwidth. Constant half-power beamwidths are needed within the frequency range with a 0.1° value within the elevation plane and the highest value possible within the azimuth plane. The feasibility study showed that a 2.5 axial ratio was acceptable from the antenna design point of view, leading to a dual reflector antenna