A multi-band antenna (1) includes a first antenna (1a), a second antenna (1b) and a grounding element (2). The first antenna (1a) includes a radiating element (10), a connecting element (20) connecting the radiating element (10) and the grounding element (2) and a feeding line. The radiating element (10) includes a first radiating section (11) working at a lower frequency, a second radiating (12) section working at a higher frequency and a third radiating section (13).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a multi-band antenna, and more particularly to a multi-band antenna used for wireless local area network.

2. Description of the Prior Art

As communication technology is increasingly improved, the weight, volume, cost, performance, and complexity of a communication system also become more important, so antennas that transmit and receive signals in a wireless communication system especially ‘draw designers’ attention. In a wireless local area network (WLAN), because the space for setting up an antenna is limited and the antenna should transmit a large amount of data, the antenna should be carefully designed. And for the requirement of small size, the antenna is needed to be able to transmit all signals of WLAN bands, 802.11b(2.4 GHz) and 802.11a(5.2 GHz).

Referring now toFIG. 1, a multi-band antenna1′ is shown and includes a radiating element2′, a grounding element4′, a feeding line5′ and a connecting element3′. The radiating element2′ comprises a first radiating portion2a′ and a second radiating portion2b′. The first radiating portion2a′ comprises a first radiating arm20′, a second radiating arm21′ and a third radiating arm22′. The second radiating portion2b′ comprises the second radiating arm2′, the third radiating arm22′ and a forth radiating arm23′. The first radiating arm20′, the second radiating arm21′, the third radiating arm22′, the grounding element4′, the connecting element3′ and the feeding line5′ compose of a first inverted-F antenna. The second radiating arm21′, the third radiating arm22′, the forth radiating arm23′, the grounding element4′, the connecting element3′ and the feeding line5′ compose of a second inverted-F antenna. The first inverted-F antenna is operated at a lower frequency, and the second inverted-F antenna is operated at a higher frequency. However, blind area unavoidably exists in the multi-band antenna1′ which influences performances of the multi-band antenna1′ in great extent.

Hence, an improved antenna is desired to overcome the above-mentioned shortcomings of the existing antennas.

BRIEF SUMMARY OF THE INVENTION

A primary object, therefore, of the present invention is to provide a multi-band antenna with simple structure, reduced size and wider bandwidth.

In order to implement the above object and overcomes the above-identified deficiencies in the prior art, the multi-band antenna comprises: a first antenna, a second antenna and a grounding element. The first antenna comprises a radiating element comprising a first radiating section working at a lower frequency, a second radiating section working at a higher frequency and a third radiating section, a connecting element, connecting the radiating element and the grounding element, and a feeder line.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to a preferred embodiment of the present invention.

Referring toFIG. 2, a multi-band antenna1according to the present invention is shown. The multi-band antenna1is made of a metal patch, and comprises symmetrically arranged first antenna1aand second antenna1b, and a common grounding element2.

The first antenna1acomprises a radiating element10, the grounding element2, a feeding line (not shown) and a connecting element20connecting the radiating element10and the grounding element2.

The radiating element10comprises a first radiating section11, a second radiating section12and a third radiating section13. The first radiating section11comprises a first radiating arm101, and the second radiating section12comprises a second radiating arm102. The third radiating section13comprises a third radiating arm103and a fourth radiating arm104. The first radiating arm101and the second radiating arm102locate in the same plane to form a first lengthwise metal arm3. The third radiating arm103is perpendicular to the first radiating arm101and the second radiating arm102and extends from the joint of the first radiating arm101and the second radiating arm102. The fourth radiating arm104is perpendicular to the third radiating arm103and extends along the direction parallel to the second radiating arm102from lower end of the third radiating arm103. The fourth radiating arm104and the connecting element20constitute a second lengthwise metal arm4. The grounding element2comprises a first grounding portion21and a second grounding portion22located in a horizontal plane perpendicular to that of the first grounding portion21. The first grounding portion21wider than the connecting element20extends from the connecting element20. The second grounding portion22extends vertically from the first grounding portion21and forms a metal patch. The first lengthwise metal arm3is parallel to the second lengthwise metal arm4and thus, forms a first notch7and a second notch8therebetween. The first notch7and the second notch8is vertically spaced by the third radiating arm103. The first lengthwise metal arm3, the third radiating arm103and the second longwise metal arm4constitute an inverted H shape frame.

The feeding line connects the radiating element10on the joint of the first radiating arm101and the second radiating arm102. The first radiating section11works at a lower frequency. The second radiating section12works at a higher frequency cooperating with the third radiating section13increase its bandwith and gain. In alternative embodiments of the present invention, the location of joint of the feeding line and the radiating element10can be changeable to alter the impedance.

The second antenna1band the first antenna1aare identical are oriented at opposite sides of the first grounding portion21to be mirror images of each other. Both of the first antenna1aand the second antenna1bare used as WLAN antennas to form a dual WLAN antenna.

A pair of mounting portions5,6respectively extend from the opposite sides of the second grounding portion22of the grounding element2and are located in the same plane as that of the first grounding portion21.

FIG. 3a test chart recording of voltage standing wave ratio (VSWR) in accordance with the multi-band antenna1. The VSWR of the antenna1is lower than2among the 2.3-2.5 GHz frequencies and the 5.725-5.875 GHz frequencies, so the multi-band antenna1satisfies current requirements.

FIGS. 4-7are horizontally and vertically polarized principle plane pattern of the multi-band antenna1operating at the resonant frequency of 2.4375 GHz and 5.725 GHz. The figures show the dual WLAN antenna work reciprocally to reduce the radiating blind areas.

While the foregoing description includes details which will enable those skilled in the art to practice the invention, it should be recognized that the description is illustrative in nature and that many modifications and variations thereof will be apparent to those skilled in the art having the benefit of these teachings. It is accordingly intended that the invention herein be defined solely by the claims appended hereto and that the claims be interpreted as broadly as permitted by the prior art.