I. Introduction
With the development of wireless communication, multiband antenna arrays are highly desired in many wireless applications, such as mobile [1]–[4] and satellite communications [5]–[7]. Although antenna arrays designed in separate radiation apertures meet the multiband requirement, large size and weight are inevitable due to low aperture utilization efficiency. However, the volumes in base station or satellite for installing antennas are very limited. To solve this problem, multiple antenna arrays operating in different frequency bands should be integrated with one radiation aperture, i.e., multiband aperture-shared antenna arrays [1]–[7], reducing the size and weight of the multiband antenna array.