Circularly polarized ground radiation antenna using planar metal loop

In this paper, a new type of compact mobile antenna that can generate circularly polarized wave is proposed. The antenna is composed of square-shaped ground plane, monopole type resonator and metal loop structure. Square-shaped ground has degenerate modes which are perpendicular. Resonant frequencies of degenerate modes are efficiently lowered by metal loop structure and are finely split by adjusting inductances inserted in the metal loops. Monopole type resonators are inserted to couple degenerate ground modes equally with feeding source. According to the measured results, the antenna has impedance bandwidth (reflection coefficient ≤ -6 dB) of 24%, axial ratio (AR) bandwidth (AR ≤ 6 dB) of 7.7% and average efficiency of 54% in the 2.4-2.5 GHz frequency band appropriate for Wi-Fi and Bluetooth.