Compact dual‐band circularly polarized filtering patch antenna using dispersive delay line

Abstract

A compact dual-band circularly polarized (CP) filtering patch antenna is proposed by adopting the dispersive delay line (DDL) in this article. The in-band and out-ofband phase differences of two orthogonal components are effectively controlled by the DDL to realize opposite polarization states. As perfect isolation is achieved between left-hand circular polarization and the righthand one in CP antenna, by controlling the parameters of DDL, four radiation nulls are presented simultaneously, and their locations are directly determined by the phase difference, thus obtains good filtering performance with compact structure. For demonstration, dualband CP patch antenna is designed at 2.4 and 5.8 GHz for WLAN applications based on DDL. The simulated and measured results of fabricated prototypes show good agreement. Good out-of-band rejection is observed in this design, which verifies the feasibility of the proposed CP filtering strategy.