Mobile terminal and method of operating antenna thereof

1. A mobile terminal comprising:

a plurality of antennas;

a main ground;

at least one sub-ground separate from the main ground and positioned adjacent to a corresponding antenna among the plurality of antennas;

at least one switch configured to switch a connection of the main ground and the at least one sub-ground; and

a controller configured to sustain or move a resonance frequency of the corresponding antenna by controlling switching of the connection of the main ground and the at least one sub-ground,

wherein the plurality of antennas comprise:

a first antenna disposed at one side of a printed circuit board (PCB) including at least one electronic component and the main ground, the first antenna being a main antenna configured to transmit and receive a wireless signal,

a second antenna disposed at another side of the PCB, the second antenna being a sub-antenna configured to receive a wireless signal transmitted from a base station, and

a third antenna configured to receive a digital broadcasting signal; and

wherein:

the first antenna and the second antenna are formed as a diversity antenna for mobile communication,

at least one second sub-ground is positioned adjacent to the third antenna and separate from the main ground and the at least one sub-ground, and

at least one second switch is configured to switch a connection of the main ground and the at least one second sub-ground according to a control signal of the controller.

2. The mobile terminal of claim 1 , wherein:

the at least one sub-ground is positioned adjacent to the second antenna and separate from the main ground; and

the at least one switch is configured to switch a connection of one of the at least one sub-ground and the main ground according to a control signal of the controller.

3. The mobile terminal of claim 2 , further comprising the controller configured to activate the at least one switch to connect the main ground and the at least one sub-ground when the second antenna is not used.

4. The mobile terminal of claim 2 , further comprising the controller configured to deactivate the at least one switch to separate the main ground and the at least one sub-ground when use of the second antenna is requested.

5. The mobile terminal of claim 1 , further comprising the controller configured to activate the at least one switch to connect the main ground and the at least one sub-ground and activate the at least one second switch to connect the main ground and the at least one second sub-ground when a traffic channel is not formed.

6. The mobile terminal of claim 1 , further comprising the controller configured to activate the at least one switch to connect the main ground and the at least one sub-ground and deactivate the at least one second switch to separate the main ground and the at least one second sub-ground when a traffic channel is not formed.

7. The mobile terminal of claim 1 , further comprising the controller configured to deactivate the at least one switch to separate the main ground and the at least one sub-ground and activate the at least one second switch to connect the main ground and the at least one second sub-ground when a traffic channel is formed.

8. The mobile terminal of claim 7 , wherein the controller is configured to determine that the traffic channel is formed when a packet data communication channel is formed.

9. The mobile terminal of claim 1 , wherein the controller is configured to activate the at least one switch to connect the main ground and the at least one sub-ground and deactivate the at least one second switch to separate the main ground and the at least one second sub-ground when a reproduction of a digital broadcasting signal is requested.

10. A method of operating an antenna of a mobile terminal comprising a plurality of antennas, the method comprising:

communicating through at least one first antenna of the plurality of antennas, the at least one first antenna disposed at one side of a printed circuit board (PCB) including at least one electronic component and a main ground, the at least one first antenna being a main antenna configured to transmit and receive a wireless signal;

determining whether use of at least one second antenna of the plurality of antennas is requested, the at least one second antenna disposed at another side of the PCB, the at least one second antenna being a sub-antenna configured to receive a wireless signal transmitted from a base station;

moving or sustaining a resonance frequency of the at least one second antenna by controlling a first switch to switch a connection of a main ground and a first sub-ground based on the determination, the first sub-ground being separated from the main ground and positioned adjacent to the at least one second antenna; and

switching a connection of the main ground and a second sub-ground according to a control signal using a second switch, the second sub-ground being positioned adjacent to a third antenna for receiving a digital broadcasting signal and separate from the main ground and the first sub-ground,

wherein the at least one first antenna and the at least one second antenna are formed as a diversity antenna for mobile communication.

11. The method of claim 10 , wherein moving or sustaining the resonance frequency further comprises separating, when use of the at least one second antenna is requested, the main ground from the first sub-ground.

12. The method of claim 11 , wherein separating comprises deactivating the first switch to separate the main ground from the first sub-ground.

13. The method of claim 11 , further comprising:

in response to a reproduction of a digital broadcasting signal being requested on the at least one first antenna, connecting the main ground and the first sub-ground, and sustaining the connection of the main ground and the first sub-ground.

14. The method of claim 10 , wherein moving or sustaining the resonance frequency comprises connecting, when use of the at least one second antenna is not requested the main ground and the first sub-ground.

15. The method of claim 14 , wherein connecting comprises activating the first switch to connect the main ground and the first sub-ground.

16. The method of claim 10 , wherein determining comprises determining, when a traffic channel is formed, that use of the at least one second antenna of the plurality of antennas is requested.