Direct Deterministic Nulling Techniques for Large Random Arrays Including Mutual Coupling

Effective approaches for interference nulling in large random planar arrays are presented. Starting from the well-known subtraction technique, it is shown that the suppression is only effective when the mutual coupling is taken into account. Moreover, for practical antennas with significant cross-polarization levels, additional efforts are required to null interference in both co- and cross-patterns. Alternative techniques are proposed to efficiently generate null patterns that are able to suppress interferers from the output of the beamformer of large arrays. In particular, a technique exploiting the polarization diversity of modern multiantenna systems is proposed to effectively suppress a large number of interferers while offering high sensitivity. Examples related to SKA1-LOW stations are presented to illustrate the performance of these techniques. Throughout these examples, the embedded element patterns obtained using fast full-wave simulation techniques are exploited to fully account for the effects of mutual coupling.