A small-size reconfigurable loop antenna for mobile phone applications with a compact volume of 55 × 5 × 3 mm3 is proposed. In addition to the traditional three loop antenna modes, namely, 0.5-λ, 1-λ, and 1.5-λ modes, the proposed loop antenna also generates another 2-λ mode. To cover more operating bands with such compact antenna volume, the reconfigurable technique is therefore applied by inserting an RF switch at the end of the proposed antenna to improve bandwidth at the low band. By combining the four working states of RF switch, the proposed antenna can cover GSM850/900, DCS1800, PCS1900, UMTS2100, and LTE2300/2500 bands with low specific absorption rate and high efficiencies.
