Design and full-wave analysis of conformal ultra-wideband radio direction finders

The design and full-wave analysis of radio direction finders (RDFs) for ultra-wideband direction-of-arrival estimation is addressed. Conformal elliptically shaped dipoles are selected as antenna sensors by virtue of their good input impedance matching property, performance robustness and conformability. In order to achieve a full angular scanning coverage in the azimuthal direction, a uniform circular direction finding array topology is adopted. The parasitic coupling between the array elements is analysed rigorously, and a dedicated calibration method is used to compensate for non-idealities of the system. In particular, a computationally efficient design procedure for radio direction finding structures is proposed. This procedure, based on a suitable iterative approach, can be usefully adopted to determine the optimal array geometry in terms of number of antenna sensors and volume occupation, while providing a good insight into the physical limitations of the system. By using the developed optimisation technique, a novel RDF operating in the frequency range between 250 MHz and 3.3 GHz is designed, and the relevant performance is thoroughly investigated in realistic operative scenarios. It has been found that the proposed system is rank-1 ambiguity-free, and can be used for tracking both narrow and wideband radio signals.