A new type of closed square ring decoupling structure is proposed in this letter, which can effectively reduce the coupling of antennas. The designed antenna is composed of two elliptical monopoles and a common ground loaded with a broadband parasitic decoupling structure. Considering the impedance matching, each antenna element is changed from the original rectangular microstrip feed to a tapered microstrip feed and etched a circular slot on the elliptical monopole patch. By comparison with the original antenna without any decoupling structure, through loading the broadband decoupling structure on the ground, the antenna isolation is improved by 10 dB in most frequency bands. Comparing simulation and measurement results, the antenna achieves better than 25 dB isolation over the whole operating band (3.3–12 GHz). By manufacturing and testing the antenna designed in this article, the excellent performance parameters obtained also prove that the antenna can be used in portable devices.
