Key Technology Research On Onboard Ground-based-beam-forming

Spacebased smart antenna has provided geostationary communication satellites with flexible multi-beam access and ability to cancel a particular direction interference. But as the complexity of the smart antenna getting higher, spacebased equipment has more difficulties to provide enough capacity for supporting multi-beam-forming operation. Ground-based-beam-forming has been successfully made up for the inadequacy of spacebased one. It is supposed to take the place of spacebased solution as mainstream. While, at the same time the transmission quality of array signal is higher, there needs to ensure the receiving signal at a lower distortion reaching the ground.Therefore in this paper, based on the research of ground based beam forming satellite system, key issues on the formation is investigated. The specific works are as follows:Firstly, this paper summarizes the Ka-band channel modeling methods briefly, and analyzes the space part and the ground part of the channel model. Then the space and ground part of channel model is given. The error performance under Ka-band is simulated, and the effect of channel fading and the influence of atmospheric dispersion is analyzed. The result shows that in a single channel, the effect of the differential group delay is equivalent to 1.13 degrees of phase.Secondly, this paper designs the Doppler and phase calibration link, and analyzes the causes in detail. Combined with the Ka band channel characteristics, simulations of Doppler and amplitude and phase calibration error and the residual error on RLS beam forming in different weather conditions are fulfilled. The results show that under the signal-to-noise ratio of 30 d B, 0.1d B amplitude error, phase error of 5 degree can be reached.Finally, this paper shows of the structure of the hybrid-beam-forming system by introducing the principle of matrix compression, then presents the methods to imply bandwidth compression. At the same time, the paper analyzes the influence of quantitative orders and transmission in noise channel. Results show that while the numbers of the array elements is greater than beam spots, compression can reduce feed link bandwidth, and will not lead to rapid deterioration in performance.Above all, this paper investigates the existing GBBF system, analyses the factors affecting the formation of ground based beamforming, and builds two complete links — channelized relay link and compression relay link, which will provide a reference for practical system design.