Tunable Circularly Polarized Ferrite-Based antennas for Passive Direction Finding

A tunable circularly polarized ferrite-based antenna array is proposed to estimate the direction of received signals without ambiguity using the applied magnetic bias to rotate the far-field phase pattern around the antenna boresight. The proposed structure can be implemented in a small area because of low coupling between antenna elements and it is capable of estimating the direction of arrival for signals coming from ±40° respect to the body coordinate of structure. This simple and compact direction finder structure is easy to fabricate and the proposed algorithm is frequency independent.