A folded loop antenna with four resonant modes

A multimode loop antenna with compact volume for mobile applications is presented in this paper. The loop antenna consists of a loop strip with a length of about 0.5λ. The loop strip is meandered to save space and bent to generate three traditional resonant modes, the 0.5-λ, 1-λ and 1.5-λ modes, and an additional higher mode, the 2-λ mode. The additional 2-λ mode is generated by adjusting the distance between the feed point and shorting point of the loop strip. The 1-λ, 1.5-λ and 2-λ modes together form an upper band with a wide bandwidth of 1.71-2.69 GHz to cover the DCS1800, PCS1900, UMTS2100, LTE2300 and LTE2500 systems. By using a matching network at the loop input, the lower band generated by the 0.5-λ mode has a bandwidth of 0.76-1.09 GHz to cover the GSM850 and GSM900 systems.