A Reconfigurable Antenna With One Slit and a Small Clearance for Nona-Band Metal-Bezel Mobile Phones

In this article, a reconfigurable antenna with one slit and a small ground clearance is proposed for nona-band metal-bezel mobile phones. The proposed antenna consists of a low-frequency band (LB) antenna and a middle- and high-frequency band and new radio (MHB&NR) antenna. The LB antenna is a monopole antenna with a lumped-element matching circuit and a switching circuit. The MHB&NR antenna consist of a monopole antenna with a lumped-element matching circuit, a parasitic branch, and a parasitic slot. The reconfigurable method, lumped-element matching method, multiple branches method, and multiple modes method are applied to cover nine bands with a small clearance of 0.5 mm. The effect of the switch on the antenna efficiency and its efficiency improvement is analyzed in detail. The working modes with its impedance matching are analyzed based on the S-parameters and the current distributions. A capacitor is applied to share the resonant branch of the LB antenna and the MHB&NR antenna with a single slit. A prototype shows that the measured −6-dB impedance bandwidths are 284 MHz (0.695–0.979 GHz), 1070 MHz (1.71–2.78 GHz), and 470 MHz (3.28–3.75 GHz), which can cover the 0.704–0.96 GHz (LB: LTE700, GSM850, and GSM900), 1.71–2.69 GHz (MHB: UMTS, GSM1800, GSM1900, LTE2300, and LTE2500), and 3.4–3.6 GHz (N78) bands. The measured efficiencies in the LB, MHB, and N78 bands are 33%–55%, 46%–62%, and 43%–53%, respectively. The proposed nona-band antenna with one slit and a small clearance of 0.5 mm is a promising candidate for modern metal-bezel mobile phones.