Analysis of Scan Blindness in a Linearly Polarized Tapered-Slot Phased Array in Triangular Lattice-Performance Improvement With Parasitic Notches

Various types of scan blindness are analyzed in a single-polarized tapered-slot phased array with triangular lattice arrangement, and a scan blindness removal strategy is proposed. In the presented analysis, two types of scan blindness are observed which have not been previously reported. First, a special case of parallel plate cavity resonance is demonstrated to cause scan blindness at a fixed frequency for E-plane scanning. Second, another cause for E-plane scan blindness is extended from previous observations, by including the fundamental mode of a half-mode open waveguide. This type of leaky-wave-induced scan blindness is limited to triangular lattices and can occur at lower frequencies compared to other types of leaky-wave blindness. In the second part of this paper, parasitic notches are proposed as an effective measure to significantly improve the E-plane scanning characteristics of the considered array by reducing the magnitude of the leaky modes. As a beneficial side-effect, these parasitic notches are also proven to improve the H-plane scanning characteristics by suppressing resonances within the stripline substrate cavity of the individual tapered-slot elements. Numerical simulations and measurements performed on a 169-element array prototype validate the analysis and confirm the effectiveness of the proposed concept for scan blindness suppression.