An optimal beamforming algorithm for phased-array antennas used in multi-beam spaceborne radiometers

Strict requirements for future spaceborne ocean missions using multi-beam radiometers call for new antenna technologies, such as digital beamforming phased arrays. In this paper, we present an optimal beamforming algorithm for phased-array antenna systems designed to operate as focal plane arrays (FPA) in push-broom radiometers. This algorithm is formulated as an optimization procedure that maximizes the beam efficiency, while minimizing the side-lobe and cross-polarization power in the area of Earth, subject to a constraint on the beamformer dynamic range. The proposed algorithm is applied to a FPA feeding a torus reflector antenna (designed under the contract with the European Space Agency) and tested for multiple beams. The results demonstrate an improved performance in terms of the optimized beam characteristics, yielding much higher spatial and radiometric resolution as well as much closer distance to coast, as compared to the present-day systems.