Antennas

[0001] The invention relates to antennas, and more particularly to antennas utilized in a portable electronic device.

[0002] Antennas are utilized in various portable electronic devices, such as notebooks, for transmitting wireless signals. With reference to FIG. 1, U.S. Pat. No. 6,686,886 discloses antennas 501 and 502 utilized in a notebook. The antennas 501 and 502 are near a screen of the notebook and transmit wireless signals. The antennas 501 and 502 are oriented in different directions to improve transmission.

[0003] The antennas 501 and 502 are flat antennas. FIG. 2 shows the detailed structure of antennas 501 and 502, which comprise a first inverted L-shaped structure (composed of metal elements 702 and 703), a second inverted L-shaped structure (composed of metal elements 704 and 708), a cable 706 and a ground element 701. The first and second inverted L-shaped structures are coupled to the ground element 701. The cable 706 comprises a data line 705 and a ground line 707, the data line 705 is coupled to the metal element 703, and the ground line 707 is coupled to the ground element 701. The first and second inverted L-shaped structures each have two different resonant frequency transmitting wireless signals with two different frequency bands. Antennas 501 and 502, however, cannot transmit wireless signals in more than three different frequency bands, for example, signals comprising GSM900, DCS1800 and WLAN signals.

[0004] Antennas are provided. An exemplary embodiment of an antenna comprises a first metal element, a second metal element, a third metal element, a ground element and a cable. The first metal element and the second metal element are connected to the ground element. The third metal element is disposed on the first metal element. The cable is coupled to the first metal element. The antenna has three different resonant frequencies (a first resonant frequency, a second resonant frequency and a third resonant frequency) transmitting three signals in different frequency bands.

[0005] The antenna of the invention transmits signals in three different frequency bands with a simpler and smaller antenna structure and obtains improved transmission effect over the conventional.

First Embodiment

[0019] The invention provides a flat antenna transmitting three wireless signals, via the principle of current coupling, in different frequency bands, and more particularly an antenna integrating inverted F-shaped, L-shaped and slot antenna structures for transmitting three wireless signals.

[0020] FIG. 3 shows an antenna 100 of the first embodiment of the invention, which comprises a first metal element 1, a second metal element 2, a third metal element 3, a ground element 4 and a cable 6. The first metal element 1 and the second metal element 2 are connected to the ground element 4. The third metal element 3 is disposed on the first metal element 1. The cable 6 is coupled to the first metal element 1. The antenna 100 has three different resonant frequencies (a first resonant frequency, a second resonant frequency and a third resonant frequency) transmitting three signals in different frequency bands. The operation of the antenna 100 is described hereafter.

[0021] As shown in FIG. 4a, the first metal element 1 and the ground element 4 together compose a first radiation element (marked by oblique lines) providing the first resonant frequency. The first metal element 1 comprises a first element body 10 and a short conductor 13. The first element body 10 comprises a first portion 11 and a second portion 12 divided by a straight line 7. The first portion 11 is longitudinal and extends in a first direction X and the second portion is an inverted L-shape. The first element body 10 and the short conductor 13 are connected to the ground element 4. The short conductor 13 is longitudinal, extending along the straight line 7, and a gap is formed between an end thereof and the first element body 10. The straight line 7 is perpendicular to the first direction X. The cable 6 comprises a data line 61 and a ground layer (ground line) 62 enclosing the data line 61. The ground line 62 is coupled to an end of the short conductor 13, and the data line 61 is coupled to the first element body 10 corresponding to the end of the short conductor 13. The first radiation element is an inverted F-shaped structure providing the first resonant frequency for transmitting a GSM900 signal.

[0022] As shown in FIG. 4b, the first metal element 1. the second metal element 2 and the ground element 4 compose a second radiation element (marked by oblique lines) providing the second resonant frequency obtained from the instance of current coupling between the first metal element 1 and the second metal element 2, particularly ground-induced current coupling between the second metal element 2 and the grounded short conductor 13. Meanwhile, current coupling also occurs between the second metal element 2 and the first element body 10. The second metal element 2 is substantially an inverted L-shape, an end thereof is connected to the ground element 4. and the other end thereof extends toward the first direction X. Slots 52 and 53 are formed between the second metal element 2 and the first metal element 1. The second radiation element transmits a DCS1800 signal.

[0023] As shown in FIG. 4c, the third metal element 3, the ground element 4, the short conductor 13 and the second portion 12 comprise a third radiation element (marked by oblique lines) providing the third resonant frequency. The third metal element 3 is oblong and disposed on the second portion 12. The third radiation element is a slot antenna structure comprising a U-shaped slot 51 for transmitting a WLAN signal.

[0024] The antenna of the invention transmits signals in three different frequency bands with a simpler and smaller antenna structure and obtains improved transmission effect over the conventional.

Second Embodiment

[0025] The invention can also be utilized in transmitting signals with in different frequencies rather than three different frequencies. FIG. 5 shows an antenna 100′ of a second embodiment of the invention, which omits the second metal element, and has the first resonant frequency (provided by radiation element marked by oblique lines in FIG. 6a) and the third resonant frequency (provided by radiation element marked by oblique lines in FIG. 6b). The second embodiment of the invention can be utilized independently or combined with other antenna structures.

Third Embodiment

[0026] FIG. 7 shows a third embodiment of the invention, which omits the first portion, and has the second resonant frequency (provided by radiation element marked by oblique lines in FIG. 8a) and the third resonant frequency (provided by radiation element marked by oblique lines in FIG. 8b). With reference to FIG. 8a, the short conductor 13 is grounded, and the second resonant frequency is obtained from grounded coupling between the second metal element 2 and the grounded short conductor 13. The third embodiment of the invention can be utilized independently or combined with other antenna structures.

[0027] While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation to encompass all such modifications and similar arrangements.