Experimental Characterization Of A Dual-Polarized Direction Finding Array For Vhf-Uhf Frequency Bands

The performance of passive DF system operating in the VHF-UHF band is hampered by the need to contain the array aperture to compact dimensions (especially when dealing with vehicular or mobile applications) and the unwanted effect of the structural component of the array. In particular, both metallic structures and cables which run near the antennas are a source of perturbation of antenna patterns (due to coupling effects) and compromise the cross-polarization purity. The characterization of the DF array becomes essential to assess the effectiveness of the array design and construction; characterization of DF arrays in the VHF-UHF band is not a trivial process due to the very large wavelengths involved, preventing the use of anechoic chambers. In this contribution, we present the experimental characterization procedure of a compact DF array for the 70-1300 MHz frequency band, solving the aforementioned issues. It comprises four different specialized subarrays enabling both dual-polarization operation and a maximum error in the estimate of the Angle of Arrival (AoA) well below 2 degrees RMS in the most of the frequency and angular interval of interest.