Study On The Adaptive Array Antenna Based On The Mobile Communication Of Small Satellite

The land mobile Satellite communication systems have a favorable commercial andmilitary application perception. The special type small satellite(STSS) communicationsystems with high flexibility and low cost can be used for remote information collecting,holding, and transferring, remote commands delivering, and remote personnel managing.The special role the STSS communication systems act as can't be displaced by anyother communication systems. Because of the complex channel environment, thepropagation of the wave of the STSS communication system is essentially a kind ofpropagation via multi-path, so the signal enhancement techniques are necessary. Thereceiver with AAA (adaptive Array Antenna) can differentiate signals from each otherby their different spatial signature. Besides, the receiver can get diversity gain frommore than one element, so as to be helpful to improve the quality of communications.The SDMA (Spatial Divided Multi-Area) based on AAA can enhance the conventionalmulti-area techniques, e.g., TDMA, FDMA & CDMA, so the spectrum efficiency canbe improved and the capacitance of the communications system can be increased. Given the sampled data of each element, the signal processing of AAA consists ofthree parts: the determination of source number, the DOA (Direction of Arrival)multi-user detection and DBF (Digital Beamforming). They are not independent, butassociated with one another. Having read a lot of transactions in the area of interest, the author aims at thetechnologies on AAA based on STSS and makes efforts to study the problems below: (1) The author fully analyzed the large-scale fading, which is resulted by the pathlosses and the shadowing effects, and the small-scale fading because of the multi-patheffects. And the full-shadowing model, which is suitable for the channel of STSS, isadopted. (2) The author studies the DOA estimation performance of MUSIC algorithm in thescenario of correlated signals and uncorrelated signals, compares the performances ofMUSIC and that of the conventional methods, and gives the simulation results. (3) The author analyzes the characteristic of the peaks of MUSIC spectrum in thesense of numerical value, uses the signed gradient algorithm two times to extract thepeaks, and gives the matrix model of the process of peak searching. Based on theanalysis of the searching process of the peaks of the two dimensional MUSIC spectrum IIIwhich contains the information of azimuth and elevation of the signal of interest, theRecursive Grid Searching Algorithm is adopted to ensure the peaks being searchedfast ,effectively and reliably. (4) In order to solve the problem of simultaneous TT&C of multi-target, the authormakes use of the prior information of the spatial position of the small satellite of interestand designs the hardware structure of the tracking system with soften antenna based onthe theory of DBF, in which the gradient tracking algorithm is adopted for theengineering purpose; (5)The author studies the structure and performance of the Rake receiver. And thestructure of two dimensional Rake receiver, which combines the advantages of both theRake receiver and the AAA, is adopted. So the spatial-temporal smoothing algorithmcan be used to distinguish each DOA of different path of different user effectively, andthe DOA can be automatically grouped with the corresponding user. Compared with theFBSS method, the spatial-temporal smoothing method can achieve higher resolution.