Dual band antenna

A dual band antenna has a ground portion, a first radiating conductor spaced from one side of the ground portion, a second radiating conductor connected between one end of the first radiating conductor and the ground portion, a third radiating conductor connected on the other end of the first radiating conductor, a fourth radiating conductor extended from the third radiating conductor, a parasitic element arranged to close to the second radiating conductor and connected to the ground portion and a feeding cable connected to the free end of the third radiating conductor. When the dual band antenna operates, the first, second and third radiating conductors obtain a first wireless location area network bandwidth covering 2.4 GHz to 2.5 GHz, and the third radiating conductor, the fourth radiating conductor and the parasitic element obtain a second wireless location area network bandwidth covering 4.9 GHz to 5.87 GHz.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a dual band antenna, and particularly to a dual band antenna capable of operating at wireless location area network bandwidth.

2. The Related Art

Rapid innovation and development upon wireless communication technology have made mobile communication products as one of the mainstream products nowadays. These mobile communication products include mobile phones, PDAs, notebooks, etc. For sharing resources and transmitting data, the mobile communication products can couple with proper communication modules for linking by wiring or wirelessly with a Local Area Network (LAN) to transmit and receive e-mail and to receive instant information such as news, stocks quotations, and so on.

In recent years, Wireless Local Area Network (WLAN) mobile communication products under IEEE 802.11a/b/g standards, such as WLAN cards for computers are gaining popularity in wireless communication market. Wherein, IEEE 802.11b/g standard is suitable for working at 2.4 GHz frequency band covering 2.412 GHz to 2.462 GHz, while IEEE 802.11a standard is suitable for working at 5 GHz frequency band covering 4.9 GHz to 5.87 GHz. Many of the WLAN mobile communication products want to be use under both IEEE 802.11a and IEEE 802.11b/g standard benefit from antennas.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a dual band antenna having a ground portion, a first radiating conductor, a second radiating conductor, a third radiating conductor, a fourth radiating conductor, a parasitic element. The first radiating conductor is spaced from one side of the ground portion. The second radiating conductor connects one end of the first radiating conductor and the ground portion. The third radiating conductor connects the other end of the first radiating conductor. The fourth radiating conductor extends from the third radiating conductor and towards the second radiating conductor. The parasitic element is arranged to close the second radiating conductor and connected to the ground portion. A feeding cable connects the free end of the third radiating conductor.

When the dual band antenna operates at wireless communication, the ground portion, the first radiating conductor, the second radiating conductor and the third radiating conductor form as a loop type antenna to obtain a first wireless location area network frequency band covering 2.4 GHz to 2.5 GHz. The third radiating conductor, the fourth radiating conductor and the parasitic element obtain a second wireless location area network frequency band covering 4.9 GHz to 5.87 GHz.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Please refer toFIG. 1. A preferred embodiment of a dual band antenna100according to the present invention is shown. The dual band antenna100has a ground portion1, a first radiating conductor2, a second radiating conductor3, a third radiating conductor4, a fourth radiating conductor5and a parasitic element6.

In this case, the ground portion1, the first radiating conductor2, the second radiating conductor3, the third radiating conductor4, the fourth radiating conductor5and the parasitic element6are all form as rectangle. The first radiating conductor2is defined opposite ends and spaced from one side of the ground portion1. The second radiating conductor3connects one end of the first radiating conductor2and the ground portion1. The third radiating conductor4connects the other end of the first radiating conductor2.

In this case, the third radiating conductor4faces to the second radiating conductor3. The fourth radiating conductor5extends from the third radiating conductor4, which is close to the first radiating conductor2. In this case, the fourth radiating conductor5extends towards the second radiating conductor3. The parasitic element6connects the ground portion1, which is arranged to close to the second radiating conductor3.

For the downsizing purpose, the ground portion1and the first radiating conductor2are bent to perpendicular to the second radiating conductor3and the third radiating conductor4. The second radiating conductor3, the third radiating conductor4, the fourth radiating conductor5and the parasitic element6are at same plane.

A feeding cable7is connected between the dual band antenna100and a wireless communication module of an electric device (not shown in figures) having a signal lead and a ground lead. One end of the signal lead of the feeding cable7connects the free end of the third radiating conductor4and one end of the ground lead connects the ground portion1.

The dual band antenna100further has an antenna fixing portion8and a cable fixing portion9. In this case, the antenna fixing portion8and the cable fixing portion form on the ground portion1of the dual band antenna1. The cable fixing portion9forms as a curving shape for holding a portion of the feeding cable7. The antenna fixing portion8has a plate80formed on both ends of the ground portion1and a through hole81opened through the plate80.

Therefore, the dual band antenna100is configured in the electric device through the antenna fixing portion8and a mating fixing portion (not shown in figures) mating with the plate80and the through hole81of the antenna fixing portion8. In this embodiment, the ground portion1, the first radiating conductor2, the second radiating conductor3and the third radiating conductor4form a loop antenna. The third radiating conductor4and the fourth radiating conductor5form as a monopole antenna. In this case, the dual band antenna100is made of thin foil.

When the dual band antenna100operates at wireless location area network bandwidth, the first radiating conductor2, the second radiating3and the third radiating conductor4obtain an electrical resonance corresponding to a half wavelength corresponding to 2.4 GHz. The third radiating conductor4and the fourth radiating conductor5obtain an electrical resonance corresponding to a quarter wavelength corresponding to 5.2 GHz. The parasitic element6inducts electromagnetic from the second radiating conductor3to obtain an electrical resonance corresponding to a quarter wavelength corresponding to 5.2 GHz for improving bandwidth of 5.2 GHz band.

Please refer toFIG. 2, which shows a test chart recording of Voltage Standing Wave Ratio (VSWR) of the dual band antenna100as a function of frequency. When the dual band antenna100operates at 2.4 GHz, the VSWR value is 1.237. When the dual band antenna100operates at 2.5 GHz, the VSWR value is 1.484. The VSWR value is 1.313, when the dual band antenna100operates at 4.9 GHz. The VSWR value is 2.292, when the dual band antenna100operates at 5.87 GHz. Therefore, the dual band antenna100obtains wireless location area network bandwidth covering 2.4 GHz to 2.5 GHz and 4.9 GHz to 5.87 GHz.

In this case, adjustment of the gap between the first radiating conductor2and the fourth radiating conductor5, and the gap between the second radiating conductor3and the parasitic element6influences VSWR value of the dual band antenna100. When the fourth radiating conductor5is adjusted to close to the ground portion1, the VSWR value of the dual band antenna100between 2.4 GHz and 2.5 GHz is increased. Therefore, the gain of the dual band antenna100between 2.4 GHz and 2.5 GHz is decreased.

In the other hand, the VSWR value of the dual band antenna100between 4.9 GHz and 5.87 GHz is increased when the fourth radiating conductor5is adjusted to close to the first radiating conductor2. Therefore, the gain of the dual band antenna100between 4.9 GHz and 5.87 GHz is decreased. When the parasitic element6is adjusted to remote from the second radiating conductor3, the VSWR value of the dual band antenna100between 4.9 GHz and 5.87 GHz is increased and the gain of the dual band antenna100between 4.9 GHz and 5.87 GHz is decreased.

According to the arrangement of the ground portion1, the first radiating conductor2, the second radiating conductor3, the third radiating conductor4, the fourth radiating conductor5and the parasitic element6, the dual band antenna100obtains wireless location area network bandwidth covering 2.4 GHz to 2.5 GHz and 4.9 GHz to 5.87 GHz.

Furthermore, the present invention is not limited to the embodiments described above; various additions, alterations and the like may be made within the scope of the present invention by a person skilled in the art. For example, respective embodiments may be appropriately combined.