Determination of locations of calibration earth stations for ground based beam forming in satellite systems

Abstract

With growing need for satellite based communication systems, there is increasing focus on the technological advancements that can reduce the cost and SWaP (Size, Weight, and Power) of a satellite payload without compromising the achieved bandwidth efficiency. In a recent technological development, the signal processing for payload antenna beamforming is moved to the ground. The resultant scheme, called Ground-Based Beam Forming or GBBF (i) provides for a significant simplification to the satellite payload design, (ii) allows for improved system performance, and (iii) results in better system flexibility. A critical requirement in the GBBF system is a real-time calibration of payload antenna array. In one scheme for GBBF calibration, several transceiver systems, called Calibration Earth Stations or CESs, are placed at strategic locations within the satellite antenna coverage. CES location determination is an important system design problem for GBBF system development, as an improper choice of locations of CESs can either result in more number of CESs than necessary (thereby increasing the system cost and the CES site maintenance concerns) and/or it can deteriorate the performance of GBBF calibration. This paper describes a solution to this problem. Two criteria that the chosen CES locations should attain are described. Determination of the requisite number of CESs and their locations is cast as a problem of multi-dimensional nonlinear optimization of the selected criteria. A solution based on the stochastic annealing method is developed and its results are presented. This approach has been successfully applied in the GBBF system development for a European GEO satellite system.