1. Field of the Invention
The present invention relates to an antenna, and more specifically to an antenna device for reducing the specific absorption rate.
2. The Related Art
Wireless communication has become extremely popular with the use of cellular telephones and other wireless devices. However, problems have arisen concerning the possibility of harmful effects of electromagnetic energy on the human body inasmuch as handheld radios, cellular telephones and other portable wireless communication devices do emit electromagnetic energy. Many studies have been conducted to closely examine the effects of electromagnetic energy on the human body to determine a safe level of exposure and how to accurately measure the level. In conjunction with this, there have been some attempts to move the source of electromagnetic energy away from the body by means of the antenna location or design. In addition, with the portable wireless communication devices developing toward the miniaturization, the space for receiving the antenna in the portable wireless communication device correspondingly decreases. As a result, it is harmful and undesirable to increases the specific absorption rate (SAR) of the antenna for the sake of raising the efficiency of the antenna, and reducing the voltage standing wave ratio.
An object of the invention is to provide an antenna device for reducing the specific absorption rate. The antenna device connected to a circuit board includes a main body and a resonance element. The main body has a first radiator which has a first radiating portion, a third radiating portion abreast of the first radiating portion, an elongated second radiating portion connected with opposite ends of the first radiating portion and the third radiating portion to show a substantially door shape, a fourth radiating portion extended outwards from a side of the third radiating portion opposite to the second radiating portion, and a fifth radiating portion extended downwardly from a free end of the third radiating portion, and stretched towards the same side of the third radiating portion as the second radiating portion, and a second radiator of strip shape extended toward the third radiating portion from an end of the first radiating portion opposite to the second radiating portion. The second radiator extends beyond a free end of the fifth radiating portion and is spaced from the third radiating portion and the fifth radiating portion. A feeding portion and a grounding portion are extended downwards from an end of a side of the second radiator opposite to the first radiating portion side by side, and away from the fifth radiating portion, for being connected with an antenna circuit and a grounding circuit of the circuit board, respectively. The resonance element has an elongated first resonating portion spaced from the main body with a predetermined distance, and a second resonating portion extended perpendicularly from an end of the first resonating portion away from the main body, for being connected with the grounding circuit of the circuit board.
As described above, the antenna device is capable of transmitting the signals from the frequency bands ranging from 880 MHz to 915 MHz, and 1710 MHz to 1785 MHz, and has an excellent performance of operation at wireless communication. Meanwhile, the antenna device is provided with the simple resonance element. The resonance element is capable of resonating with the signals from the frequency band ranging from 880 MHz to 915 MHz, which decreases the SAR values of the antenna device, consequently, for reducing the harm to the users when the users use the portable electronic device.
The invention, together with its objects and the advantages thereof may be best understood by reference to the following description taken in conjunction with the accompanying drawings, in which:
With Reference to
The first radiating portion 141 has an end opposite to the second radiating portion 142 extended towards the third radiating portion 143 to form a second radiator 15. The elongated second radiator 15 extends beyond a free end of the fifth radiating portion 145 and is spaced away from the third radiating portion 143 and the fifth radiating portion 145. A connecting portion 11 is extended downwardly from an end of an outer side of the second radiator 15 away from the third radiating portion 143. The connecting portion 11 is of substantially rectangular shape. Two ends of a bottom side of the connecting portion 11 are extended downwardly and deflected inwardly, and then bent obliquely and upwardly to form a feeding portion 12 and a grounding portion 13. The feeding portion 12 and the grounding portion 13 are substantially V-shaped and spaced from each other. Herein, the first radiating portion 141, the second radiating portion 142, the third radiating portion 143, the fourth radiating portion 144 and the second radiator 15 are disposed at the same plane.
The resonance element 20 of substantially L shape has an elongated first resonating portion 21, and a second resonating portion 22 extended perpendicularly from an end of a long side of the first resonating portion 21. The second resonating portion 22 is a short strip shape. In this embodiment, the resonance element 20 is made of copper foil.
Please refer to
When the antenna device 100 operates at wireless communication, a current is fed from the feeding portion 12, runs through the connecting portion 11 and reaches the second radiator 15 to gain a total electrical length corresponding to a quarter of wavelength of the global system for mobile communication (GSM) 900, for receiving and sending signals from the frequency band ranging from 880 MHz to 915 MHz. The current is fed from the feeding portion 12, runs through the connecting portion 11 and reaches the first radiator 14 to generate a total electrical length corresponding to a quarter of wavelength of the digital cellular system (DCS) 1800, for receiving and sending signals from the frequency band ranging from 1710 MHz to 1785 MHz. The total electrical length of the resonance element 20 corresponds to one quarter of wavelength of the GSM 900 and is capable of resonating with the signals from the frequency band ranging from 880 MHz to 915 MHz.
Please refer to
As described above, the antenna device 100 is capable of transmitting the signals from the frequency bands ranging from 880 MHz to 915 MHz, and 1710 MHz to 1785 MHz, and has an excellent performance of operation at wireless communication. Meanwhile, the antenna device 100 is provided with the simple resonance element 20. The resonance element 20 is capable of resonating with the signals from the frequency band ranging from 880 MHz to 915 MHz, which decreases the SAR values of the antenna device 100, consequently, reducing the harm to the users when the users use the portable electronic device.
The foregoing description of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. Such modifications and variations that may be apparent to those skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims.