Multi-Band Folded Slot Antenna for Handset

In this paper, the multi-band small size handset antenna using slots is proposed and fabricated. It has the size of (WxLxH)40x18x7mm and support 5 bands of GSM 850 (824~894㎒), EGSM(880~960㎒), DCS1800 (1710~ 1880㎒), PCS1900(1850~1960㎒) and UMTS (1920 ~2170㎒). Generally, a slot antenna has the size of λ/2, but it is too long to be applied to handset in low frequency. Nevertheless, the reason to use slot structure for antenna here is that slot antenna has the characteristics which resonates in balance mode by itself. Three techniques are applied to reduce the slot length in low frequency band - Slot Center Feeding method using microstrip line, Substrate with 1mm thickness and er-4.4, Dumbbells shaped slot. Using all three methods, we can totally reduce the slot length about 45% off in comparison with that in air condition. In addition, the shape of slot antenna is folded to be suitable for the space of handset body. To make multi-band characteristics, Two slots and two different kinds of feeding methods are used ? Slot Center Feeding Method and Slot Offset Feeding Method, which enable us to tune the low and high frequency band independently.