adaptive antenna array
spatial signal processing
visibility zone of the radar
V.T. Ermolayev, A.G. Flaksman, I.V. Dushko, A.V. Panfilov
The earth's surface renders significant influence on shaping the visibility range of the radar. The return signal accepted by antenna array elements represents a superposition of a forward signal, and also set of signals, re-reflected from the earth's surface. In the case of an arbitrary relief and electrodynamic properties of the earth's surface for using the radar’s potentials to detect and track air targets it is ne-cessary to use adaptive methods of shaping the visibility range of the radar.
The adaptive signal processing in the antenna array consists in using on reception and on transmission weight vectors coinciding with amplitude-phase distribution of a return signal in elements of AA. The potential efficiency of adaptive methods of shaping a visibility range which is reached in the case of an ideal estimation of amplitude-phase distribution of a return signal in the elements of antenna array, that is at extreme major signal/noise ratios. It is accepted in this case to term processing optimum and its efficiency is extremely accessible (potential) for the adaptive processing.
The realization of spatial treatment in the AA assumes an amplitude and phase adjustment in each element of AA, not only on reception, but also on transmission. However frequently amplitude control on transmission conjugates to considerable technical difficulties. Quazioptimal processing therefore is of interest, which differs from optimum only by weight vector on transmission. The phases of weighting coefficients coincide with phases of a return signal in the elements of antenna array, and the amplitudes are set identical. Such processing can be used, for example, in the case of the solid-state transmitter application in the radar. Moreover, frequently it is convenient to be restricted to adaptive signal processing only on reception, and on transmission to use fixed directional coupler.
In the present work the adaptive methods of shaping visibility range of the radar with antenna array in the conditions of an arbitrary relief and electrodynamic properties of the earth's surface are offered. Present methods assume execution of two series operations: 1) maximum probable estimation of amplitude-phase distribution of a return signal in the elements of antenna array on the basis of final number of access of entering process; 2) using the obtained estimation as weight vectors of antenna array on reception and on transmission. The losses in a signal/noise ratio because of errors of estimating amplitude-phase distribution of a return signal in the elements of antenna array are explored. The results of simulation indicating sufficiently high efficiency of adaptive methods of shaping vision range are given.