TCM-Based Hepta-Band Antenna With Small Clearance for Metal-Rimmed Mobile Phone Applications

A hepta-band antenna with high efficiency, small clearance, and simple structure for metal-rimmed smartphones is proposed in this letter. The proposed antenna occupies only 71 × 5 mm
²
of the total clearance, and it is mainly composed of a system ground, a metal rim with two gaps, and two shorting strips. The theory of characteristic modes is used to analyze the entire structure. All resonant characteristic modes (CMs) in the target frequency are traced, and their characteristic current distributions are analyzed. By using an L-shaped capacitive exciter, three CMs are excited at the lower bands, and an inverted L-shaped branch is utilized for improving the impedance matching at higher bands. The measured 6 dB impedance bandwidths were 800-1000 and 1700-2780 MHz, respectively, and they can cover seven operating bands. The measured efficiencies were 62%-85.7% at the lower band and 66.9%-91% at the higher band.