Small Loop-type Mobile Antenna with Less Interference of Nearby Conductors for Wi-Fi Application

A small loop-type mobile antenna with less interference of nearby conductors for Wi-Fi application is proposed. The proposed antenna has a small volume of 8£4£3mm 3 to be easily implemented within mobile devices and a simple structure using chip capacitors without any extra matching network. In this paper, we place a LCD under the proposed antenna to discuss the efiects of conductors. The proposed antenna has less efiect to the LCD and radiates e-ciently over Wi-Fi band. The i6dB bandwidth was measured as 120MHz from 2.38 to 2.5GHz, and the measured antenna e-ciency is 50.2%. 1. INTRODUCTION Recently, the smart phone is widely used in our life to do many things such as social network services (SNS), a media player, a camera and web browser. For customer satisfaction, mobile device manufacturers tend to design a smart phone which has a large and high-resolution display, a sensitive touch panel and compact design. Because of these demands, an antenna which is applied in mobile devices is strongly required to reduce its size on the printed circuit board (PCB). To reduce the size of an antenna, various methods have been reported in several reports (1{4) such as suitably designing shorting structures of planar inverted-F antenna (PIFA) and using high permittivity. However, those methods were needed to test proposed antennas under the practical condition to guarantee its performances because the performance of an antenna can be afiected by changes in circumstances around the antenna, especially nearby conductors. In this paper, we proposed a small loop-type mobile antenna with less interference of nearby conductors for Wi-Fi application. To describe efiects of nearby conductors, we arranged a 45 £ 78 £ 1:75mm 3 liquid crystal display (LCD) under the ground plane as a nearby conductor. The resonant frequency and input impedance of an antenna are controlled by changing the values of chip capacitors without extra matching circuits around a clearance. The result shows a quite good afiordable bandwidth with suitable realized e-ciency over Wi-Fi band even though the proposed antenna is fully covered with the LCD. 2. ANTENNA DESIGN