Analysis of common-mode resonances in arrays of connected dipoles and possible solutions

A prototype array of dual polarized connected dipoles has been manufactured. The feed structure is composed by two orthogonal 8 times 8 elements for each polarization (128). The operational frequency ranges from 6 to 9 GHz (40% relative bandwidth). Preliminary measurements highlighted the presence of unpredicted common-mode resonances excited in the vertical feeding lines. An analysis of the common-mode excitation is carried out and exit strategies for a design of a resonance-free connected array are presented.