Broadband circularly polarized printed monopole antenna with protruded L-shaped and inverted L-shaped strips

A novel approach in the design of broadband circularly polarized antennas is presented in this article. The design uses a simple monopole structure with a triangular tapered feed. Right-/left-hand circular polarization (CP) is achieved by protruding L-shaped strip and inverted L-shaped strip along the left/right radiating edge of the monopole. It is proposed that the 3-dB axial ratio bandwidth (AR-BW) can be enhanced when the length of these strips is equal to (g)/4 at the center frequency of their respective CP bands. This principle is verified by fabricating the prototype on 1 mm thick FR4 substrate occupying a compact area of 0.19 (0) x 0.19 (0). From the measurement results, it is observed that the overlapped bandwidth (S-11-10 dB and AR3 dB) of the antenna is 129.04% (1.38-6.4 GHz) which covers all the major WLAN bands including the WiMAX. The proposed antenna has bi-directional radiation characteristics with a broadside gain of 3.49 dBic in the CP band.