Compact Tunable Coupled-fed Loop Antenna for Multi-band LTE/WWAN Operation in the Mobile Phone

A small-size reconfigurable coupled-fed loop antenna for multi-band LTE/WWAN mobile handset is presented. The antenna volume is 5 × 10 × 30 mm^3 only, while the protruded ground has a width of 30 mm for mounting electronic components. The proposed antenna is consisted of a loop strip and a driven strip. Through the driven strip capacitively coupled to the loop strip, the antenna can generate a quarter-wavelength loop resonant mode to form the antenna's lower band to cover the GSM850/900 bands (824~960 MHz). The simple driven strip is also an efficient radiator to excite a resonant mode for the antenna's upper band to cover the GSM1800/1900/WCDMA Band 1 bands (1710~2170 MHz). Moreover, when the chip inductor connected to the loop strip has been adjusted from 0 to 12 nH, the antenna's lower band can be shifted to lower frequency and cover the LTE Band 17 band (704~746 MHz). This tunable technique can allow the loop antenna to cover more operating bands without adding the antenna volume. Detailed operating principle and performances of the proposed antenna are discussed in the article.