Innovative Multi-Feed-Per-Beam Reflector Antenna for Space-Borne Conical-Scan Radiometers

We present an antenna for use on conical-scan space-borne radiometers in C band and demonstrate that stringent radiometric requirements can be met. The antenna consists of a 5 m offset reflector fed by a focal plane array in a multi-feed-per-beam configuration, so far never used in ocean observation missions. We use distinct element beams and two optimization routines for obtaining element excitation amplitudes and phases, and with either routine, and in both x- and y-polarization, compliant beams, with footprint < 20 km, distance to coast < 20 km and accuracy < 0:25 K, are obtained. These results may pave the way for use of focal plane arrays with digital beamforming in future radiometric ocean observation missions

Multi-Beam Focal Plane Arrays with Digital Beamforming for High Precision Space-Borne Remote Sensing

The present-day ocean remote sensing instruments that operate at low microwave frequencies are limited in spatial resolution and do not allow for monitoring of the coastal waters.This is due the difficulties of employing a large reflector antenna on a satellite platform, and generating high-quality pencil beams at multiple frequencies. Recent advances in digital beamforming focal-plane-arrays (FPAs) have been exploited in the current work to overcome the above problems. A holistic design procedure for such novel multi-beam radiometers has been developed, where (i) the antenna system specifications are derived directly from the requirements to oceanographic surveys for future satellite missions; and (ii) the numbers of FPA elements/receivers are determined through a dedicated optimum beamforming procedure minimizing the distance to coast.This approach has been applied to synthesize FPAs for two alternative radiometer systems: a conical scanner with an off-set parabolic reflector, and stationary wide-scan torus reflector system; each operating at C, X and Ku bands. Numerical results predict excellent beam performance for both systems with as low as 0.14% total received power over the land

Focal Plane Array Breadboard For Advanced Multiple Beam Radiometer Antennas

The detailed design and RF analysis of a breadboard made by 35 x-polarized and 32 y-polarized Vivaldi antennas, placed 0.67 wavelength from each other and located above a finite ground plane, are described. The breadboard constitutes a representative part of the feed array illuminating a conical scan or push-broom antenna for next generation microwave radiometers for ocean observation. The analysis are done at 6.9 GHz including mutual coupling between the elements, and in two commercial software, i.e. CST and the MoM add-on to GRASP

Multibeam focal plane arrays with digital beamforming for high precision space-borne ocean remote sensing

The present-day ocean remote sensing instruments that operate at low microwave frequencies are limited in spatial resolution and do not allow for monitoring of the coastal waters. This is due to the difficulties of employing a large reflector antenna on a satellite platform, and generating high-quality pencil beams at multiple frequencies. Recent advances in digital beamforming focal-plane arrays (FPAs) have been exploited in this paper to overcome the above problems. A holistic design procedure for such novel multibeam radiometers has been developed, where: 1) the antenna system specifications are derived directly from the requirements to oceanographic surveys for future satellite missions and 2) the numbers of FPA elements/receivers are determined through a dedicated optimum beamforming procedure minimizing the distance to coast. This approach has been applied to synthesize FPAs for two alternative radiometer systems: a conical scanner with an offset parabolic reflector and a stationary wide-scan torus reflector system, each operating at C -, X-, and Ku-bands. Numerical results predict excellent beam performance for both systems with as low as 0.14% total received power over the land

Ultra-High Performance C & L-Band Radiometer System for Future Spaceborne Ocean Missions

A next-generation real-Aperture spaceborne radiometer system for high-quality ocean measurements is discussed. Instead of illuminating the antenna reflector by a classical feed array of horn antennas in a one-feed-per-beam configuration, a multi-feed-per-beam configuration is chosen. Each antenna beam is thus created by adding the outputs from many small antenna elements in the feed array, thus providing an antenna beam of unsurpassed quality. This solves the classical polarization purity and land/sea contamination issues. The concept requires many microwave receivers and fast analog-To-digital converters as well as fast digital signal processing onboard the satellite. This is discussed, and resource budgets, especially concerning power, are provided

Novel Multi-Beam Radiometers for Accurate Ocean Surveillance

Novel antenna architectures for real aperture multi-beam radiometers providing high resolution and high sensitivity for accurate sea surface temperature (SST) and ocean vector wind (OVW) measurements are investigated. On the basis of the radiometer requirements set for future SST/OVW missions, conical scanners and push-broom antennas are compared. The comparison will cover reflector optics and focal plane array configuration

Novel Multi-Beam Radiometers for Accurate Ocean Surveillance

Novel antenna architectures for real aperture multi-beam radiometers providing high resolution and high sensitivity for accurate sea surface temperature (SST) and ocean vector wind (OVW) measurements are investigated. On the basis of the radiometer requirements set for future SST/OVW missions, conical scanners and push-broom antennas are compared. The comparison will cover reflector optics and focal plane array configuration