The Miniaturization of Multi-Band Planar Inverted-F Antenna

• Main Authors: Ya-Chung Yu, 游雅仲
• Other Authors: Jenn-Hwan Tarng
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/89464157417566971479

碩士 === 國立交通大學 === 電信工程系所 === 96 === For the multisystem applications, the antenna of a handset not only needs small size but also covers multi bands, which means that the antenna must have multi-resonating paths in a limitary size. Due to each radiating element of each frequency band is reduced such that the radiation efficiency is not good and the bandwidth is narrow. These critical parameters are trade-off one another, therefore, it is difficult to keep good performance in a compact antenna of multi-band. PIFA ( planar inverted-F antenna) is the popular type of antenna in the mobile phone market. PIFA can reduce effectively physical length of the antenna with a shorted pin which acts capacitance load and is near the feed. In conventional PIFA design, there are two popular techniques for the requirement of multi-band. Firstly, use parasitic element to increase the resonating modes, but this way would to increase the area of the antenna. Secondly, use the embedded U-shaped slits to create multi-resonating paths in main radiating element, but the radiating element is reduced, so the radiation efficiency is not good. In this paper, a novel miniaturization technique of multi-band PIFA is proposed, which makes the antenna to reuse the radiating element to radiate every frequency band. It not only reaches multi-band but also keeps good performances and small size. The modification is that the shorted pin acts short-circuit load and locates at the end of antenna instead of the function of the shorted pin in conventional PIFA. The proposed PIFA can be modeled by a half-wave transmission line impedance transformer (TILT) of short-circuited load form. For the requirement of multi-band, it adds parasitic folded branches to increase resonating current paths. Therefore, the antenna is equivalent to the parallel multi-TLITs. With changing resonate frequency, the parallel multi-TLIT is similar as a current switch to change the current path with the short-circuited load and radiate. The size of the proposed PIFA and the ground plane are 30mm×20mm×4mm and 30mm×43mm. The covered frequency bands included GSM900, DCS, PCS, UMTS, Bluetooth/WLAN, WiMAX, HiperLAN/2 bands, and an additional band (4600~4800MHz). Moreover, the antenna has a nearly omni-directional radiation pattern and a reasonable peak gain of 1dBi to 4.8dBi.