1. Field of the Invention
The present invention relates to an antenna, and more particularly to a wide band antenna that has multiple resonant modes and sufficient bandwidths.
2. Description of Related Art
Wireless telecommunication technologies develop rapidly recently years and various wireless products are marketed popularly. One of most important components in wireless product is an antenna. The quality of an antenna directly effects the stability of the communication of the wireless product with other wireless devices. Due to various wireless products are implemented under different wireless telecommunication protocols within different bandwidths, antennas are preferably designed to cover multiple bandwidths. Furthermore, antennas are sized smaller and smaller in order to fit portable wireless products that are designed more and more compact.
With reference to FIG. 1, a conventional antenna is F-shaped and comprises a resonant length, a resonant mode, a ground plane (10), a radiating patch (12), a grounding conductor (14), a through hole (15) and a feeding conductor (16). The resonant mode has a bandwidth, a central frequency and a wavelength corresponding to the central frequency. The radiating patch (12) is suspended over the ground plane (10). The grounding conductor (14) is mounted on the ground plane (10) and holds the radiating patch (12). The through hole (15) is defined through the ground plane (10). The feeding conductor (16) is mounted through the through hole (15) and is connected to a circuit on a wireless product. However, the antenna has the resonant length being about a quarter of the wavelength of the resonant mode, which limits the minimal size of the antenna and disallows the antenna to fit some compact portable wireless products.
With reference to FIG. 2, U.S. patent application publication No. 2003/0103010 discloses a “double-band antenna” comprising a patch conductor (2). The patch conductor (2) has a slot, a feed pin (25), a short pin (26) and two current paths (23, 24). The slot is zigzag and defined in the patch conductor (2). Currents running respectively along the current paths (23, 24) stimulate two different resonant modes to create two bandwidths. The double-band antenna may be sized small to fit compact wireless products. However, each bandwidth of the double-band antenna is limited and insufficient.
To overcome the shortcomings, the present invention provides a wide band antenna to mitigate or obviate the aforementioned problems.