I
CUBIC GPS ANTENNA AND MOVABLE TERM INAL DEVICE USING
THE SAME
Technical Field
The present invention relates to a cubic GPS(Global Positioning System) antenna capable of receiving GPS satellite signals from various directions, and more particularly, to a cubic GPS antenna, in which plane antennas are mounted on each side of a case of a mobile terminal device, and which combines and outputs signals transmitted to the plane antennas using a power combiner.
Moreover, the present invention relates to a cubic GPS antenna capable of combining and outputting signals transmitted to small plane antennas using a power combiner by attaching the small plane antennas on each side of a polyhedron for receiving GPS satellite signals.
Background Art
In general, a GPS(Global Positioning System) has been steadily studied and developed for military and industrial purposes since it had been developed at the Department of Defense in U. S. in 1972. The GPS is a system capable of detecting the position of a fixed or moving object from the arrival time of satellite signals received from a number of satellites, whose positions are defined. To detect the exact position from a GPS receiver, it is necessary to receive the satellite signals transmitted from each satellite over a predetermined level. Conventionally, to receive the satellite signals, a micro strip antenna, which has a high dielectric constant and is arranged on a plane surface, has been used in the GPS receiver. The conventional antenna is low in gain, and thereby, combined with an amplifier to process information by amplifying the GPS signals.
The main beam of the antenna must be always directed to the sky. Such antenna has no problem in the GPS receiving device, but in a mobile terminal device having a GPS function, such as a mobile phone on which the GPS receiver is attached, it is difficult to use the GPS function because the mobile terminal device in itself can be positioned in various directions in the case that the mobile terminal device is put in a pocket. That is, because the GPS antenna attached on the mobile terminal device is in a planar structure, a receiving level of the satellite signals is greatly lowered and it is difficult to grasp the position if the radial direction of the main beam of the plane antenna and the satellite are not identical with each other. The reason is that in the plane antenna, the half power beam width whose receiving level is 1/2 of the maximum received angle is restricted to 70-78°, and thereby, it cannot be expected that the plane antennas located on a certain place receive the satellite signals.
Nevertheless, because the plane antennas are the most suitable for a compact mobile phone, the studies and developments of the plane antennas used in the mobile phone have been performed widely.
Disclosure of Invention
Accordingly, it is an object of the present invention to provide a cubic
GPS(Global Positioning System) antenna capable of overcoming the restriction of a beam incident angle of a plane antenna, that is, the problem of a narrow half power beam width.
It is another object of the present invention to provide a cubic GPS antenna to a mobile terminal device capable of changing a direction of a plane antenna, which is mounted on the mobile terminal device, at any time, thereby receiving GPS information even during the movement without regard to the position of the mobile terminal device.
In an aspect of the present invention, the present invention provides a cubic GPS antenna including: plane GPS antennas mounted on each side of a polyhedron; and a power combiner electrically connected with the plane GPS antennas and adapted to combine signals received from the plane GPS antennas. Preferably, the polyhedron includes a hexahedron.
Preferably, the power combiner includes a hemispherical or rectangular micro strip cavity.
Preferably, the coupling coefficient between the power combiner and the plane GPS antennas is about -ldb, and the isolation between the power combiner and the plane GPS antennas is -30db or less.
Preferably, the plane GPS antennas and the power combiner are in the form of a square of the same size, for example, 9><9χ0.3mm in width by length by height, and may be in the form of a rectangle and have other sizes.
Preferably, the cavity mounted inside the power combiner is in the form of a rectangle, and has first to fourth ports provided on long sides thereof and fifth and sixth ports provided on short sides, wherein the first and fifth ports are input ports connected with the plane GPS antennas, and the sixth port is an output port for outputting the combined signals.
In another aspect, the present invention provides a cubic GPS antenna including: plane GPS antennas mounted on each side of a mobile terminal device in such a manner that at least one or more sides of the mobile terminal device direct GPS satellites even though the mobile terminal device is located at any position; and a power combiner electrically connected with the plane GPS antennas and adapted to combine signals received from the plane GPS antennas. Preferably, the mobile terminal device is one selected from a mobile phone, a radio PDA and a computer system.
In a further aspect, the present invention provides a cubic GPS antenna including: plane GPS antennas mounted on a body with a predetermined volume
for covering an opposed space radially; and a power combiner electrically connected with the plane GPS antennas and adapted to combine signals received from the plane GPS antennas.
Brief Description of the Drawings
Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which: FIGS, la to Id are pattern views showing an example of a slotted antenna and a printed loop antenna, which are plane antennas, used in the present invention;
FIG. 2a is a configuration view of a cubic GPS(Global Positioning System) antenna, to which a hemispherical micro strip cavity is applied, according to a preferred embodiment of the present invention;
FIG. 2b is a configuration view of a cubic GPS antenna, to which a multi- port power combiner having a rectangular micro strip cavity, according to another preferred embodiment of the present invention;
FIG. 3 is a view showing an example to which the cubic GPS antenna of the present invention is applied;
FIG. 4 is a view showing another example to which the cubic GPS antenna of the present invention is applied; and
FIG. 5 is a pattern view of five ports for connecting the rectangular cavity of FIG. 2b and the antennas, and one port for combining and outputting signals.
Best Mode for Carrying Out the Invention
The present invention will now be described in detail in connection with
preferred embodiments with reference to the accompanying drawings. For reference, like reference characters designate corresponding parts throughout several views.
It would be appreciated to the skilled in this field that while the present invention has been described with reference to the particular illustrative embodiments, they are just provided for helping understanding the present invention, and the present invention can be embodied without the particular embodiments.
Moreover, if it is decided that detailed description of the related published functions and structures make the subject matters of the present invention obscure, the description will be omitted.
Referring to FIG. 2a, a mobile terminal device, such as a mobile phone, a radio PDA, or a computer system, has plane antennas Al, A2, A3, A4 and A5 mounted on each side thereof, and GPS satellite signals received from the plane antennas are combined in a power combiner Psys and outputted to a signal output terminal Pout.
The power combiner Psys can be in various types, but as shown in FIG. 1, in the present invention, it is in a semicircular micro strip disk type. It is preferable that the power combiner Psys is mounted inside the mobile terminal device without occupying additional space.
FIG. 2b shows a cubic GPS antenna to which a multi-port power combiner using a rectangular micro strip cavity is applied.
The multi-port power combiner Psys can be mounted in various forms. For example, there are a method for mounting a Wilkinson power combiner(2- input, 1 -output) in a multi-stage parallel form, and a method for realizing the multi-port in a single-stage form using characteristics of the cavity.
Referring to FIG. 5, the cavity mounted inside the power combiner is in the form of a rectangle, and includes first to fourth ports P2, P3, P4 and P5
provided on long sides thereof, and fifth and sixth ports P I and Pout provided on short sides: the first to fifth ports PI to P5 being input ports connected to the plane GPS antennas; and the sixth port Pout being an output port for outputting combined signal. As the plane antennas Al, A2, A3, A4 and A5, various types of conventional antennas can be used. That is, there are micro strip patch antennas, distributed line L-C cavity antennas, slotted rectangular micro strip patch antennas as shown in FIG. 1, printed loop antennas, and so on. Moreover, only one type of antennas may be used or various types of antennas may be used together.
The power combiner Psys serves to combine current input from lots of branch circuits and to transmit the combined current to one output circuit, and must combine the signals received from the plane GPS antennas Al, A2, A3, A4 and A5 in the optimum condition. For this, it is necessary to match impedance between the ports of the cavity, which are mounted on the power combiner Psys, well. In this case, the reflection is minimized.
Preferably, the coupling coefficient between the power combiner and the plane GPS antennas is about -ldb, and the isolation between the power combiner and the plane GPS antennas is -30db or less. If the coupling coefficient and the isolation do not satisfy the above conditions, the signals cannot be transmitted properly, and thereby, the combining effect can be reduced.
FIG. 3 shows an example that the cubic GPS antenna is applied.
As shown in the drawing, in case of a mobile phone 100, for example, the plane antennas Al, A2, A3, A4 and A5 are mounted on five sides of the mobile phone 100 excepting the rear side, and the power combiner Psys is mounted on the rear side. The number of the plane GPS antennas can be selected suitable for the type or design of the mobile terminal device.
For example, the power combiner Psys can be 9χ9χ0.3mm in width by
length by height. Preferably, the power combiner Psys has two ports provided on each long side and one port provided on each short side of the rectangular cavity Mc to match impedance between the ports of the cavity Mc mounted inside the power combiner Psys. Preferably, the plane GPS antennas Al, A2, A3, A4 and A5, which are
9χ9χ0.3mm in width by length by height, are mounted on each side of the mobile phone 100, and the ports and the plane GPS antennas Al, A2, A3, A4 and A5 are connected by a micro strip line.
At this time, the impedance matching can be optimized by controlling width, bending and the whole length of the micro strip line.
FIG. 4 shows another example to which the cubic GPS antenna is applied.
The plane GPS antennas Al to A6 are mounted on five sides excepting a certain side of a hexahedron 110, and the power combiner (not shown), which is electrically connected with the plane GPS antennas Al to A6 by the micro strip line and combines the signals received from the plane GPS antennas, is mounted on the certain side, preferably, the side which is attached to the mobile terminal device 100.
The hexahedron 110 to which the cubic GPS antenna is applied can be mounted on the side, where the existing antenna of the mobile phone 100 is located, parallel with the existing antenna.
While the present invention has been described with reference to the particular illustrative embodiments, it is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention. For example, the cubic GPS antenna can be applied to a polyhedron, such as a hemisphere, a sphere, a cylinder, or others. It is important to mount the plane GPS antenna to cover opposed spaces.
Therefore, the present invention is not to be restricted by the above embodiments, but is restricted only by the appended claims or their equivalents.
Industrial Applicability
As described above, the present invention is applied to the mobile terminal device whose surface opposed to the GPS satellite is changed. Because the plane antennas are mounted on each side of the mobile terminal device even though the direction of the main beam of the antennas is not identical with the GPS satellite, the surface opposed to the GPS satellite always exists, and the present invention can maintain receiving sensitivity over a predetermined level.
Especially, in case of a call center managed by a portable communication unit, such as the mobile phone, it is necessary to check the position of the mobile phone. Because the mobile phone to which the present invention is applied can receive the GPS satellite signals three-dimensionally, it can solve the receiving level drop due to a narrow half power beam width of simple plane GPS antennas.