1. Field of Invention
The present invention relates to an EMC (electromagnetic compatible) metal-plate antenna and a communication system using the same, and particularly to a built-in EMC antenna and a communication system using the same, which is capable of effectively reducing possible electromagnetic coupling between the antenna and other electronic elements without an isolation spacing.
2. Description of Related Art
Along with the thriving development of wireless communications, various communication products and communication technologies are being emerged in flourish, and the wireless communication products have gradually become an indispensable part in people's living. With drastic competitions in the market, a wireless communication apparatus is required to be lighter, thinner and smaller. Thus, a built-in antenna and the performance thereof play a significant role.
Modern wireless communication products at least include an antenna, a battery, a RF circuit module (radio frequency circuit module) and other electronic components. High-level product even includes a digital camera lens of CCD (charge coupling device). Therefore, if the spacing between the antenna and other components is not large enough, a negative electromagnetic coupling occurs, which leads to the degradation in the antenna performance. Hence, to apply an antenna in a wireless communication apparatus, the EMC influence of the surroundings must be considered, which increases the difficulty of design.
To reduce the electromagnetic coupling, an isolation spacing between the antenna and other components is preserved to sustain the antenna performance. However, the isolation spacing preservation reduces usable spaces inside the wireless communication apparatus, and also limits a wireless communication apparatus to be light and compact. Besides, since the electromagnetic coupling between the antenna and other components would be varied by the position change of other components, large effects on the antenna performance are expected.
Some conventional arts, for example U.S. Pat. No. 6,856,294 (‘compact, lower profile, single feed, multi-band, printed antenna’) and U.S. Pat. No. 6,717,548 (‘dual- or multi-frequency planar inverted F-antenna’) disclose built-in antennas. In U.S. Pat. No. 6,856,294, a spacing of about 6 mm between an antenna and a shielding metal case of a RF circuit module is required to assure the circuit characteristics (frequency, impedance, efficiency) to be normal. In U.S. Pat. No. 6,717,548, a spacing of about 7 mm is required not only between an antenna and a shielding metal case of a RF circuit module, but also between an antenna and a shielding metal wall of a digital camera lens, such that normal circuit characteristics can be obtained.
As a matter of fact, the above-mentioned antenna designs did not consider the shielding of an antenna itself yet. Therefore, when such kind of antennas is disposed near other electronic components, an extra spacing is required for reducing the electromagnetic coupling between the antenna and other electronic components, which results in an inefficient usage of the limited available space. If the spacing preserved is not sufficient, a frequency shift and an impedance change occur, which affect the signal quality and largely reduce the antenna performance due to the electromagnetic coupling.
In high-level mobile communication products, components disposed near to an antenna are usually a digital camera lens, a RF circuit module and a battery. In general, the above-mentioned components have their own shielding metal cases. However, the conventional antenna does not have its own shielding. When the distance between the antenna and the shielded components is too small, the antenna performance would be degraded due to a strong electromagnetic coupling. To reduce the coupling, an extra spacing between the conventional antenna and the components is required, which leads to an inefficient usage of the avaiable space inside the mobile communication apparatus. Besides, when the position relation changes between the antenna and other components, the antenna performances would be varied, and the antenna needs to redesigned, leading to a labor waste.
From the above description, an EMC (electromagnetic compatible) metal-plate antenna and a communication system using the same are demanded, which are capable of effectively reducing possible electromagnetic coupling between the antenna and other electronic components without an isolation spacing.