1. Field of the Invention
This invention relates to an antenna, more particularly to a dual band antenna.
2. Description of the Related Art
FIG. 1 illustrates a conventional dual band antenna 1 that operates both within the GSM 900 MHz bandwidth and the DCS 1800 bandwidth, that is mounted on a circuit board 100 of a mobile phone, and that includes a radiating element 10, feeding and grounding points 11, 12, and feeding and grounding lines 14, 15. The radiating element 10 is rectangular in shape, is spaced apart from and is disposed parallel to the circuit board 100, and has opposite first and second sides 101, 102 and opposite third and fourth sides 103, 104. The feeding point 11 is provided on the radiating element 10 proximate to a junction of the first and third sides 101, 103 of the radiating element 10. The radiating element 10 is formed with a slot 13 that extends from the fourth side 104 toward the feeding point 11. The grounding point 12 is provided on the radiating element 10 proximate to a junction of the second and third sides 102, 103 of the radiating element 10. The feeding line 14 connects electrically the feeding point 11 to the circuit board 100. The grounding line 15 connects electrically the grounding point 12 to the circuit board 100.
The aforementioned conventional antenna 1 is disadvantageous in that further reduction in size of the radiating element 10 is not feasible while maintaining operability within the GSM 900 MHz bandwidth and the DCS 1800 bandwidth.