However, they are well suited to parallel processing and now provide a very practical alternative due to recent advances in VLSI circuit technology. The direct-solution methods do not suffer from this problem, but tend to be suitable only more » for digital processing and are more expensive from the computational point of view. However, their rate of convergence is fundamentally limited and too slow for some applications. The closed-loop methods are very cost-effective and suitable in principle, for either analog or digital processing. These fall into the two main categories of closed-loop methods and direct-solution methods. Various approaches to the practical implementation of adaptive null steering are then discussed. The basic theory is first outlined in the context of sidelobe cancellation systems as well as general antenna arrays. « lessĪ brief theoretical review of adaptive null steering is presented. Relevant and useful reference material is also included in the form of appendices describing the relationship between different polarization representations and demonstrating the conditions under which Maxwell's equations can be considered to be scale-invariant. The model demonstrates dramatic performance improvement when the filter is used, showing that usable performance can be achieved even when the target depolarization is so severe that the cross-polarized signal is more than an order of magnitude stronger than the desired co-polarized signal. The benefit of the application of a polarization more » filter is demonstrated by modeling a monopulse radar system viewing a dihedral corner reflector.
Two kinds of polarization filters, suitable for linear polarization, are described for mitigating the effects of depolarization due to cross-polarization scattering. The mechanism through which man-made targets can introduce cross-polarization components into the scattered field is explained. The use of a shroud to reduce multipath interaction with nearby objects is also described. The polarimetric behavior of this type of antenna is examined.
The monopulse response of radar systems utilizing a short-focal-length offset-fed parabolic reflector can be compromised by depolarization of the signal by the target and by multipath scattering from nearby objects.
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