An Antenna With a Stair-Like Ground Branch for Octa-Band Narrow-Frame Mobile Phone

An antenna with a small nonground portion (56 × 5 mm
²
) for 5.7 in octa-band mobile phones is presented in this letter. Owing to the stair-like ground branch, the width of the nonground portion is 5 mm (0.013 λg at frequency 0.8 GHz), and the area of ground clearance is only 280 mm
²
. By utilizing the space with a small value of the electric field, the antenna's size can be reduced without worsening the performance. The optimized structure can generate the high band that covers GSM1800, GSM1900, UMTS, LTE2300, and LTE2500 bands (1710-2690 MHz). Moreover, a double-resonant mode is generated in the low band for LTE700, GSM850, and GSM900 bands (704-960 MHz). A prototype is fabricated, and the measured -6 dB impedance bandwidths are 310 MHz (690-1000 MHz) and 1270 MHz (1680-2950 MHz). Meanwhile, the measured patterns, efficiencies, and gains are also obtained. This antenna is promising to utilize in the future.