Patent Application
20080001831
The above aspects and features of the present invention will be more apparent by describing certain exemplary embodiments of the present invention with reference to the accompanying drawings, in which:
Certain exemplary embodiments of the present invention will now be described in greater detail with reference to the accompanying drawings.
In the following description, the identical drawing reference numerals are used to refer to the equivalent elements, even in different drawings. The matters specified in the following description, such as detailed construction of the inventive apparatus, as well as descriptions of separate elements thereof, are provided for exemplary purposes only, in order to assist in a comprehensive understanding of the invention. Also, certain well-known functions or constructions are not described in detail, because they would obscure the invention in unnecessary detail.
Generally, speech quality of a mobile terminal is determined by a reception rate of radio waves transmitted from a base station. For good radio wave reception characteristics, a planer inverted F antenna (PIFA) having omi-directional characteristics is employed as the mobile terminal antenna
The PIFA includes a radiator 10, a feed pin 15, a shorting pin 20, and a ground 30. A radiation preventer 40 (shown in
The radiator 10 is separated from the ground 30 by a predetermined interval and runs in parallel with the ground 30. The radiator 10 operates to emit electromagnetic wave radiation.
The feed pin 15 interconnects the radiator 10 and the ground 30 and provides electric current to the radiator 10. The shorting pin 20 interconnects the radiator 10 and the ground 30 to drain the current circulating in the radiator 10 to the ground 30.
The ground 30 can be formed on a circuit board in either an integral or a separate manner. Due to the presence of the ground 30, the antenna size of λ/2 can be reduced to λ/4. Accordingly, the length of the ground 30 is about λ/4.
The radiation preventer 40 is arranged to face the radiator 10 and is centered with respect to the ground 30. The radiation preventer 40 is spatially separated from the ground 30 and is positioned in parallel with the ground 30. The radiation preventer 40 includes a plurality of radiation preventing bars 45 arranged in series and positioned at intervals, and a connector 35, which connects the radiation preventing bars 45 with one end of the ground 30.
The radiation preventing bar 45 can be implemented using a metallic wire or a metallic plate. The longitudinal direction of the radiation preventing bar 45 is parallel to the direction of vertical polarization of the antenna The length of the radiation preventing bar 45 is approximately λ/4, which is also the length of the ground 30.
The connector 35 has a shape of a strip, and connects one end of each of the radiation preventing bars 45 with one end of the ground 30. The radiation preventing bars 45 and the ground 30 are spatially separated by a distance corresponding to the thickness of the connector 35. In one example, the radiator 10 may be mounted at the upper end of the ground 30, while the connector 35 is mounted at the lower end of the ground 30.
More specifically, the radiator 10 may be mounted at the upper end of one side of the ground 30, while the connector 35 is mounted at the lower end of the other side of the ground 30.
In the conventional mobile terminal antenna, the ground 30′ carries (−) charge and the radiator 10′ carries (+) charge. The electric current flows from the (+) charge to the (−) charge. The aforesaid electric current flow results in generation of fringing field, due to the fact that the electromagnetic waves from the radiator 10′ reach the ground 30′ as shown in
By contrast, in the mobile terminal antenna according to an exemplary embodiment of the present invention, the radiator 10 is positioned on one side of the ground 30, while the radiation preventer 40 is positioned on the other side thereof. Thus, the radiator 10 and the radiation preventing bar 45 carries (+) charge, whereas the ground 30 carries (−) charge, as shown in
It should be noted that impedance of the antenna is generally determined based on Equation 1.
Z
in
=j*Z
0 tan βl [Equation 1]
When calculating the impedance of the radiation preventer 40 based on Equation 1, Zin is an input impedance of the radiation preventer 40 and l is the length of the radiation preventer 40. Because the length l of the radiation preventer 40 is λ/4, the value of Zin becomes ∞. Thus, the fringing field is not generated because the electric current cannot flow into the radiation preventer 40.
Referring to
In contrast, the mobile terminal antenna in accordance with the present invention produces higher degree of electromagnetic wave directivity toward the z-axis as shown in
In the inventive antenna configuration, with the radiation decreasing in the direction of −z-axis, the gain of the antenna increases. According to measurement of the actual gain, the conventional mobile terminal antenna has the gain of 2.019 dB, whereas the mobile terminal antenna of the present invention has the gain of 2.502 dB. That is, the gain of the mobile terminal antenna of the present invention is improved by approximately 0.5 dB, in comparison with the conventional antenna
In one embodiment of the invention, conductive paints are applied to inner surfaces of the casing 50 of the mobile terminal in order to block the radiation of the electromagnetic waves radiated from circuit parts mounted on the circuit board. In an embodiment of the present invention, the conductive paints are spread over the inner surfaces of the casing 50 in a strip shape. To this end, a plurality of paint strips 65 is formed along the direction of the electric field generated at the antenna and arranged at intervals across the electric field. It is preferable to set the length of the paint strip 65 to λ/4, as the length of the radiation preventing bar 45
A paint link 55 is formed at one end of the paint bars 65 to interconnect the paint bars 65, and to electrically connect them to the ground. The paint link 55 protrudes from the inside of the casing 50 by a certain amount such as to establish an electrical contact with the circuit board 70 carrying the ground.
Referring now to
Thus, the embodiment of the inventive mobile terminal, provides the lengthy radiation preventing bar 45 or paint strip 65 along the direction of the electric field. The mobile terminal antenna of the present invention produces the radiation pattern having the omi-directional characteristics with respect to the z-axis. Therefore, the fringing field is eliminated and the amount of electromagnetic radiation generated in the direction of the human body is reduced. Additionally, the inventive antenna is characterized by enhanced performance characteristics due to the increased gain.
In the embodiment of the present invention, the PIFA is exemplified as the mobile terminal antenna. It is to be appreciated that the present invention is applicable to any antennas, which can be mounted on the mobile terminal and have omi-directional characteristics.
As set forth above, the amount of electromagnetic radiation in the direction of the human body can be reduced by altering the radiation emission pattern, while the performance of the antenna can be simultaneously enhanced.
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2006-0060440 | Jun 2006 | KR | national |
