Mechanism and Elimination of Scan Blindness in a T-Printed Dipole Array

Abstract

In this article, the scan blindness in a T-printed dipole is analyzed, and an elimination strategy is proposed. First, the main cause of scan blindness is analyzed. The scan characteristics are obtained using an active element pattern (AEP) with an infinite rectangular lattice arrangement. Based on the propagation of a guided wave along the antenna row and the electric-field ( $E$ -field) distribution observed during simulations, an equivalent circuit model for a unit cell of the T-printed dipole is obtained. A quasi-transverse electromagnetic (TEM) guided wave is predicted using the dispersion relation curve obtained from the equivalent circuit, and it is proven that the calculated curve is in good agreement with the eigen mode simulations and measured trajectory of the scan blind angle, for different frequencies. Next, slits and stubs are introduced as parasitic structures to eliminate the scan blindness and improve the antenna scan range. To confirm the effects of these parasitic elements, a linear array simulation is performed, which confirms the suppression of a quasi-TEM guided wave. Analysis of the active reflection coefficient and dispersion diagram indicates that the scan characteristics have been improved by the addition of parasitics. Four types of array prototypes are fabricated and their measurements validate the scan blindness prediction and confirm the proposed mechanism of scan blindness and its improvements.