Re-configurable built-in antenna for portable terminal

1. A re-reconfigurable built-in antenna of a portable terminal, the antenna comprising:

an antenna radiator having a feeding pad electrically connected to a feeding portion of a main board of the terminal and at least one ground pad disposed in a position different from that of the feeding pad for selectively establishing a direct electrical connection to a ground portion of the terminal; and

a switching element, commonly connected to the at least one ground pad of the antenna radiator, for selectively establishing an electrical connection to the ground portion by a switching operation,

wherein the antenna radiator changes an electrical length of the antenna radiator by using the selective electrical connection of the ground portion so as to have various operational frequency bands and radiation properties.

2. The antenna of claim 1 , wherein a position of each of the ground pads is selected by considering a space for installing the antenna radiator depending on a specific operational frequency band and radiation property of the antenna radiator.

3. The antenna of claim 1 , wherein the number of ground pads to be formed is 2 so that the two ground pads are respectively branched off from a pattern of the antenna radiator and are electrically connected to an output electrode of the switching element, and so that a common electrode is electrically connected to the ground portion.

4. The antenna of claim 1 , wherein the electrical length of the antenna radiator is changed in structure by branching off one ground pad from the antenna radiator and by turning on/off the ground pad by the switching element.

5. The antenna of claim 3 , wherein the antenna radiator operates as at least one of an Inverted-F Antenna (IFA), a loop-type antenna, and an Inverted-L Antenna (ILA) according to an operation of the switching element.

6. The antenna of claim 1 , wherein a matching circuit is provided in series or parallel to a ground line between the ground pad and the switching element or between the switching element and the ground portion.

7. The antenna of claim 6 , wherein the matching circuit is one or more combinations of a Capacitance (C), a Resistance (R), and a Reactance (L).

8. The antenna of claim 1 , wherein the switching element is at least one of a Single Pole Double Throw (SPDT), a Single Pole Single Throw (SPST), and a Single Pole Triple Throw (SP3T).

9. A multi-band portable terminal, the terminal comprising:

a main board;

an antenna radiator having a feeding pad electrically connected to a feeding portion of the main board and at least one ground pad disposed in a position different from that of the feeding pad for selectively establishing a direct electrical connection to a ground portion of the terminal;

a switching element, commonly connected to the at least one ground pad of the antenna radiator, for selectively establishing an electrical connection to the ground portion by a switching operation; and

a controller for controlling the switching element so that the antenna radiator has an electrical length corresponding to a frequency band used by the terminal.

10. The terminal of claim 9 , wherein a position of each of the ground pads is selected by considering a space for installing the antenna radiator depending on a specific operational frequency band and radiation property of the antenna radiator.

11. The terminal of claim 9 , wherein the electrical length of the antenna radiator is changed in structure by branching off one ground pad from the antenna radiator and by turning on/off the ground pad by the switching element.

12. The terminal of claim 10 , wherein the antenna radiator operates as at least one of an Inverted-F Antenna (IFA), a loop-type antenna, and an Inverted-L Antenna (ILA) according to an operation of the switching element.

13. The terminal of claim 9 , wherein the switching element is at least one of a Single Pole Double Throw (SPDT), a Single Pole Single Throw (SPST), and a Single Pole Triple Throw (SP3T).