Wireless communication device and feed-in method thereof

1. A wireless communication device, comprising:

a slot antenna, comprising a first feed-in terminal and a second feed-in terminal, wherein the first feed-in terminal is different from the second feed-in terminal;

a radio-frequency (RF) signal processing module, for processing an RF signal transmitted or received by the slot antenna; and

an RF signal diplexer, coupled between the slot antenna and the RF signal processing module, for splitting up the RF signal into a first frequency component and a second frequency component during transmission, and synthesizing the first frequency component and the second frequency component into the RF signal during reception, the RF signal diplexer comprising:

a first feed-in network, coupled between the first feed-in terminal of the slot antenna and the RF signal processing module, for transmitting the first frequency component of the RF signal and attenuating the second frequency component of the RF signal; and

a second feed-in network, coupled between the second feed-in terminal of the slot antenna and the RF signal processing module, for attenuating the first frequency component of the RF signal and transmitting the second frequency component of the RF signal.

2. The wireless communication device of claim 1 , wherein the first feed-in network comprises:

a first transmission line, coupled to the first feed-in terminal of the slot antenna and the signal processing module, for transmitting the first frequency component of the RF signal and attenuating the second frequency component of the RF signal;

wherein a length of the first transmission line is equal to or greater than a quarter wavelength of the second frequency component.

3. The wireless communication device of claim 1 , wherein the second feed-in network comprises:

a second transmission line, coupled to the second feed-in terminal of the slot antenna and the signal processing module, for transmitting the second frequency component of the RF signal and attenuating the first frequency component of the RF signal; and

an open stub, shunted between the first transmission line and the slot antenna, for attenuating the first frequency component of the RF signal;

wherein a length of the first transmission line and a length of the open stub are equal to a quarter wavelength of the first frequency component.

4. The wireless communication device of claim 3 , wherein the first feed-in network further comprises:

an extending transmission line, cascaded between the open stub and the slot antenna, for extending the second transmission line, to compensate a distance from the second feed-in terminal of the slot antenna to the second feed-in network;

wherein a length of the extending transmission line is substantially equal to the quarter wavelength of the second frequency component.

5. The wireless communication device of claim 1 , wherein a first frequency of the second frequency component is substantially twice a frequency of the first frequency component.

6. The wireless communication device of claim 1 , wherein the slot antenna further comprises:

a substrate;

a first radiating element, formed on a first layer of the substrate, for transmitting and receiving the first frequency component of the RF signal;

a second radiating element, formed on the first layer of the substrate, for transmitting and receiving the second frequency component of the RF signal;

a connecting bridge, coupled between the first radiating element and the second radiating element, for connecting the first radiating element and the second radiating element;

a first feeding microstrip line, formed on a second layer of the substrate, for transmitting and receiving the first frequency component of the RF signal; and

a second feeding microstrip line, formed on a second layer of the substrate, for transmitting and receiving the second frequency component of the RF signal.

7. The wireless communication device of claim 6 , wherein the first radiating element and the second radiating element respectively comprise a first slot and a second slot formed along a first direction.

8. The wireless communication device of claim 7 , wherein the first feeding microstrip line and the second feeding microstrip line are formed along a second direction perpendicular to the first direction.

9. A feed-in method for a slot antenna comprising a first radiating element corresponding to a first frequency component of a radio-frequency (RF) signal and a second radiating element corresponding to a second frequency component of the RF signal, the feed-in method comprising:

adjusting a first feed-in network such that a first input impedance of the first feed-in network matches with the first radiating element and mismatches with the second radiating element, wherein the first input impedance of the first feed-in network mismatching with the second radiating element attenuates the second frequency component of the RF signal, and wherein the first radiating element is different from the second radiating element; and

adjusting a second feed-in network such that a second input impedance of the second feed-in network matches with the second radiating element and mismatches with the first radiating element, wherein the second input impedance of the second feed-in network mismatching with the first radiating element attenuates the first frequency component of the RF signal.

10. The feed-in method of claim 9 , wherein the step of adjusting the first feed-in network comprises:

cascading a transmission line to the slot antenna, for transmitting the first frequency component of the RF signal and attenuating the second frequency component of the RF signal.

11. The feed-in method of claim 9 , wherein the step of adjusting the second feed-in network comprises:

cascading a transmission line to the slot antenna, for transmitting the second frequency component of the RF signal; and

shunting an open stub between the transmission line and the slot antenna, for filtering out the first frequency component of the RF signal.

12. The feed-in method of claim 11 , wherein the step of adjusting the second feed-in network further comprises:

cascading an extending transmission line between the transmission line and the slot antenna, for compensating a distance from the second feed-in network to the slot antenna.