On the Number of Degrees of Freedom in Dual-Polarized GNSS Adaptive Arrays

It is known that a dual-polarized adaptive array with N elements has a maximum of 2N-1 degrees of freedom for beamforming. For small global navigation satellite system (GNSS) adaptive arrays, we show that this maximum can be easily achieved if the interferer polarizations are random. For the case of right-hand circularly-polarized (RHCP) interferers however, we show that the maximum degrees of freedom can only be achieved if the element patterns are asymmetric in the principal E- and H-planes.