Filtering Antenna Design in Metal-Bezel Smartphones With a Small Clearance for Interference Suppression

The increasing number of antennas and small antenna space in modern smartphones pose a potential risk of in-device coexistence (IDC) interference. In this article, the filtering antenna design applied in metal-bezel smartphones with a small clearance for IDC interference suppression is proposed. The proposed antenna consists of an medium-high band (MHB) antenna and a GPS L1/WiFi-2.4 antenna. Both the MHB antenna and the GPS L1/WiFi-2.4 antenna are composed of an inverted-F antenna (IFA) and a parasitic branch. Each IFA is shorted to the ground via a capacitor. Also, a neutralization line is linked between the MHB antenna and the GPS L1/WiFi-2.4 antenna. The parasitic branches and the grounding capacitors introduce radiation nulls to improve the isolations at the GPS L1 and the MHB band. The neutralization line improves the isolation at the WiFi-2.4 band. A fabricated prototype demonstrates that, by employing the parasitic branches, decoupling capacitors, and neutralization line, the high isolations of 25 and 30 dB at GPS L1 and WiFi-2.4 bands, respectively, are achieved. Also, the isolations across all the bands are over 20 dB. In addition, the average efficiencies are more than 40%. The proposed filtering antenna with high isolation demonstrates significant potential to reduce IDC interference for modern smartphones.