Equivalent circuit and scanning capabilities of long slot arrays with TEM parallel-feed excitation

A detailed analysis of phased arrays of long slots excited by transverse electromagnetic (TEM) fields, is presented. First, a previously developed model for infinite uniform arrays and infinitely-extended slots is reviewed. The explicit form established for the active admittance allows to derive a network representation of the array. The physical meaning of each component in the circuit is revealed, providing valuable insight on the radiation mechanism. Then, scan blindness phenomena in the principal planes are investigated to assess the scanning capabilities, with reference to arrays covered by a single dielectric slab. The frequency behavior of pattern nulls is presented. The onset of blind spots is heuristically linked to the array period and to the electrical thickness of the cover through parametric studies, in order to provide design criteria to achieve large scan ranges. A novel condition on the array period for the appearance of blind angles in H-plane is demonstrated.