1. Field of the Invention
The present invention relates to a portable wireless terminal. More particularly, the present invention relates to an antenna device equipped in a portable wireless terminal.
2. Description of the Related Art
As the electronic communication industry develops, portable wireless terminals are becoming lighter, slimmer, smaller, and more multi-functional. For example, a speaker device capable of realizing melodies of various harmonies is installed, and a color display device with millions of pixels is implemented. Also, in addition to a call function, a portable wireless terminal now typically provides a music listening function through a Moving Picture Experts Group (MPEG) Audio Layer 3 (MP3) Player (MP3P). Furthermore, the portable wireless terminal provides not only various game contents using the display device but also a function of receiving a radio signal, a Digital Multimedia Broadcasting (DMB) signal, etc.
In general, a portable wireless terminal uses an antenna that transmits and receives signals. If it is desired to provide the portable wireless terminal with greater radio wave transmission/reception, the antenna is designed to be large so as to have high directivity. In such a case, the spacing distances between other parts within the portable wireless terminal decrease in order to maintain the lightness and smallness of the portable wireless terminal. Therefore, it is difficult to secure the space for the larger antenna and improve the transmission/reception performance of the terminal. In addition, a Transmit (Tx) output of a designed antenna should not be allowed to exceed a reference value permitted in each country.
For example, an antenna for transmitting and receiving a signal in a Frequency Modulation (FM) frequency band may be implemented with a single antenna (e.g., an earphone connected to an external connector). In this case, a problem arises in that a Transmit (Tx) output of the antenna for transmitting and receiving the signal in the FM frequency band exceeds a reference value permitted in each country. FIG. 8 is a graph illustrating an antenna performance of a conventional antenna transmitting and receiving singles in the FM spectrum. FIG. 9 is a table illustrating an FM Tx output regulation specified by the USA and Europe. In a case where an earphone antenna is used, the Tx output is 98 dB which exceeds an output regulation specified by each country as shown in FIG. 9. Accordingly, a need exists for an antenna device that increases the reliability of communication while not exceeding output regulations of each country.