Eight-Band Antenna With A Small Ground Clearance for LTE Metal-Frame Mobile Phone Applications

This letter presents a compact eight-band monopole antenna whose size is 70 mm × 7 mm × 6 mm for LTE metal-frame mobile phones. The mainly radiating part of the proposed antenna is the metal frame. There are three gaps with the same size of 1 mm in the frame, and these gaps divide the antenna into two parts. Besides, a match circuit is used to enlarge the bandwidth and make the lower band matched. The advantage of the proposed antenna is that eight bands can be covered with a metal frame under the condition of only a 7 mm ground clearance. A prototype is manufactured and tested. The measured -6 dB impedance bandwidths are 375 MHz (0.675-1.05 GHz) and 1.2 GHz (1.6-2.8 GHz). The LTE700, GSM850, GSM900, GSM1800, GSM1900, UMTS, LTE2300, and LTE2500 bands are covered. The measured efficiencies are 52.7%-78.7% at the lower band and 45.6%-81% at the higher band. The measured gains are 0-2.1 dBi at the lower band and 1.6-3.6 dBi at the higher band.