I. Introduction
Antenna arrays based on substrate integrated waveguides (SIWs) are becoming popular because they are low profile, compact, efficient, and low-cost designs at millimeter waves [1]. The millimeter wave band offers wider bandwidth with compact system components, which is most desirable for mobile and portable communication systems. However, SIW has a high Q-factor and it also exhibits low radiation efficiency for a planar antenna array [2]. A dielectric resonator antenna (DRA) is an excellent candidate to offer low loss when excited by an SIW [3]–[5].