A single-feed tri-band circularly polarized dual-annular slot antenna for wireless applications

A novel single-feed tri-band circularly polarized (CP) dual-annular slot antenna is presented. The antenna structure is composed of two nonconcentric annular slots fed by a novel inverted h-shaped microstrip line configuration. Compared to most of the previously reported tri-band CP antenna structures, the proposed antenna has low profile, compact in size, and easy to fabricate on the single-layer PCB. It is easy for the antenna to match all the three frequency bands by employing an h-shaped feeding line. The antenna also can provide a conical radiation pattern at the third band. A sample design of a tri-band CP antenna operated at 1.58, 2.42, and 3.0 GHz is realized. Details of the experimental results compared with simulated results are presented and discussed. The proposed compact tri-band CP antenna design is suitable for mounting onto the mobile communication devices and portable positioning systems.