JP2011019111A - Composite antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna which is incorporated in the inside of information terminal devices such as a personal computer, or a PDA, allows stable communication without generating interference across a plurality of bands, and is small and has simple structure.SOLUTION: Three radiation elements 1a, 2a, 3a opposite to ground plates 1c, 2c, 3c are provided, the three radiation elements 1a, 2a, 3a are electrically connected to the ground plates 1c, 2c, 3c by short-circuit plates 1b, 2b, 3b, and internal conductors 4a1, 4b1, 4c1 of coaxial cables 4a, 4b, 4c are connected to feeding points P1a, P2a, P3a of the radiation elements 1a, 2a, 3a, respectively.

Description

  The present invention relates to a multi-frequency wideband composite antenna that combines a plurality of antennas incorporated in an information terminal device such as a personal computer, a PDA (portable information device), a mobile phone, or a VICS. More specifically, the present invention relates to a composite antenna that is small in size and capable of stable communication without interference.

The present applicant has previously described a composite antenna in which the short-circuit plates of the individual antenna elements are arranged opposite (facing) as a composite antenna that prevents interference with a composite antenna in which individual antennas having different specifications such as resonance frequencies are integrated. An antenna was proposed (see Patent Document 1).

However, although this method can be easily realized with two antennas, in the case of three or more individual antennas, there is only a method of arranging the short-circuit plates of the individual antennas in a three-dimensional manner. In this case, Since a large space is inevitably required, and a built-in antenna for a PC or the like allows only a limited space on the same plane on the left and right, there is a problem that the method of Document 1 cannot be applied to such applications. .

On the other hand, when individual antennas with different specifications such as resonance frequency are arranged in the same plane in the left and right rows, the distance between adjacent antennas is 15 mm or more in order to avoid interference between the antennas and ensure stable communication. Therefore, there is a limit to downsizing.
Furthermore, in view of the recent situation in which the number of antennas is increased to more than 3 to meet the demand for multi-frequency, none of the methods is the optimal method.

JP 2008-31168 A

Therefore, an object of the present invention is to realize stable communication without interference in a composite antenna combining a plurality of individual antennas having different specifications such as a resonance frequency incorporated in a personal computer or an information terminal device such as a PDA. And it is providing the composite antenna suitable for size reduction.

The present inventors pay attention to the fact that the potential difference between the ground plates of each antenna due to the high-frequency current flowing in the ground plate of each antenna is a cause of the interference, and no mutual interference occurs between the antennas. It came to find the ground (earth) processing method.

That is, according to the present invention, the radiating element is electrically connected to the ground plate via the short-circuit plate and is fed by the feeding coaxial cable, and has the following requirements a to c: A composite antenna is provided.
a. As the radiating element, at least three or more antennas having different lengths are arranged in a line;
b. Each radiating element is connected to each ground plate via a respective short-circuit plate;
c. At least a part of each ground plate is connected by the outer conductor of the coaxial cable for power supply.

According to the present invention, the following remarkable effects can be expected.
(1) Since no interference occurs even though the antennas are arranged close to each other, stable transmission / reception is realized.
(2) Due to the close arrangement, the antenna element, and thus the antenna, can be reduced in size and space.
(3) The manufacturing process is simplified because only the conventional composite antenna is replaced by soldering the feeding coaxial cable with an intermediate strip.

It is a perspective view which shows the example of the composite antenna of FIG. 1 which concerns on this invention. It is a front view which shows the element part of the antenna of FIG. FIG. 3 is a perspective view showing another aspect of the composite antenna element according to the present invention. FIG. 3A shows an aspect in which the ground plate is a common ground (collective ground), and FIG. A mode in which a part of the housing is a housing ground is shown. 4A and 4B are diagrams illustrating VSWR characteristics of the composite antenna of FIG. 1, in which FIG. 4A is a VSWR characteristic diagram in a LAN band, and FIG. 4B is a VSWR characteristic diagram in a Wi-Max band.

  Hereinafter, the aspect of the composite antenna of this invention is demonstrated based on the example which provided three separate antennas, referring an accompanying drawing.

1 and 2, reference numerals (1), (2), and (3) denote three independent individual antennas having different specifications such as resonance frequency, and radiating electrode elements (1a) and (2a) having different lengths. , (3a), and these elements are juxtaposed on the same line in the figure. In the following description, “radiating electrode element” is simply abbreviated as “element”. (1b), (2b) and (3b) are attached to the elements (1a), (2a) and (3a), respectively, and these elements are connected to the respective ground plates (1c), (2c) and (3c). It is a short circuit board connected to. These short-circuit plates (3a), (3b), (3c) extend from the approximate center of each ground plate (4a), (4b), (4c) to the same length in the vertical direction. Here, the ground plates (1c), (2c), and (3c) are connected and integrated by connecting portions (1d) and (2d). These elements extend in the same direction while being parallel to the ground plates (1c), (2c), and (3c).
Further, (P1a), (P2a), and (P3a) are feeding points provided in the elements (1a), (2a), and (3a), respectively, and (P1b), (P2b), and (P3b) are feeding powers, respectively. Corresponding to the points (P1a), (P2a), (P3a), these are earth points provided on the respective ground plates (1c), (2c), (3c). (4a), (4b), and (4c) are power supply coaxial cables, and (4a1), (4b1), and (4c1) are respectively inside the power supply coaxial cables (4a), (4b), and (4c). The conductors (4a2), (4b2), and (4c2) are external conductors of the feeding coaxial cables (4a), (4b), and (4c), respectively. In this case, the inner conductors (4a1), (4b1), and (4c1) are connected to the feeding points (P1a), (P2a), and (P3a), respectively, and similarly, the outer conductors (4a2), (4b2), (4c2) are also connected to the ground points (P1b), (P2b), and (P3b), respectively.

Further, the feeding coaxial cables (4a) and (4b) use intermediate strip processed coaxial cables in which the intermediate portion is strip processed so that the outer conductor is exposed.
For the coaxial cables (4a) and (4b) for feeding, the sheath at one intermediate portion is peeled off, and the outer conductors (4a2-1) and (4b2-1) are on the ground plates (2c) and (3c), respectively. Solder-connected to Q1 and Q2 near the ground point (P2b) and near (P3b) located at.

FIG. 4 shows the antenna VSWR characteristics of the antenna shown in FIG. 1, which was prepared using the materials and dimensions shown in the after-lifting embodiment. From FIG. 4, in the antenna using the broadband antenna element of the present invention, each antenna has both the LAN band shown in FIG. 4 (a) and the Wi-Max band shown in FIG. 4 (b). It can be seen that stable transmission / reception is achieved without interference over the three bands of the LAN band and the Wi-Max band while maintaining the VSWR characteristics of the above.

What is characteristic in the embodiment described above is that at least a part of each of the ground plates (1c), (2c), (3c) is an outer conductor (4a2-1) of the feeding coaxial cables (4a) and (4b). ) And (4b2-1).
By doing so, the ground plates (1c), (2c), (3c) of each antenna (1), (2), (3) and the ground potential of the three feeding coaxial cables (4a), (4b) , (4c) outer conductors (4a2), (4b2), (4c2) are at the same potential, so that it is possible to prevent the occurrence of noise due to the potential difference. Accordingly, the elements (1a), (1b), (1c) Even if they are arranged close to each other, stable communication can be realized without fear of interference.

In the antenna element arrangement according to the present invention, if the distance between the antennas is 5 mm or more, there is no concern about interference, and as a result, miniaturization as a composite antenna is realized. However, since the space efficiency of the antenna shape decreases if the distance between the antennas is too large, it is desirable that the distance between the antennas be in the range of 3 mm to 8 mm.

In the present invention, the lengths of the elements (1a), (1b) and (1c) are set according to the resonance frequency, and are usually set to 20 to 40 mm when the resonance frequency is 2 GHz to 6 GHz. Further, the widths of the elements (1a), (1b), and (1c) are not particularly limited and may be usually in the range of 1 to 5 mm.

The short-circuit plates (1b), (2b), and (3b) may have a height of 10 mm or less and a width in the range of 0.5 mm to 5 mm from the viewpoint of miniaturization of the antenna.
The connection plates (1d) and (2d) are for connecting the ground plates (1c), (2c), and (3c) to each other, and need not be special shapes, such as flat plate shapes, angle shapes, etc. Various forms can be selected. Further, the widths of the connecting plates (1d) and (2d) only need to ensure the necessary strength, and are usually in the range of 1 mm to 3 mm.

Since miniaturization of the antenna shape is an important point in the present invention, the total area of the elements (1a), (2a), (3a) including the short-circuit plates (1b), (2b), (3b) is 500 mm 2 or less. Preferably there is. On the other hand, for the ground plates (1c), (2c) and (3c), in order to obtain stable antenna operation, the necessary minimum area (mm2) is λ / 4 * λ / 4 (λ is a wavelength) or more. I need it. Therefore, when more stable antenna operation is desired, it is preferable to increase the area as long as space permits.

As the material of the antenna element described above, a conductive metal such as white (white copper), copper, iron, or brass is preferably employed. In producing the antenna element, the single metal plate may be punched out by electric discharge machining to form an integrally punched body of all elements extending from the element body to the ground plate. Alternatively, it is also useful to obtain a desired antenna element shape by etching the metal film in a state where a metal thin film such as a copper foil is attached to the flat insulating substrate.

In feeding power to such an antenna element, the inner conductors (4a1), (4b1), (4c1) of the feeding coaxial cables (4a), (4b), (4c) are respectively fed to the feeding points (P1b), On the other hand, the outer conductors (4a2), (4b2), and (4c2) of the cable may be connected to the ground points (P1b), (P2b), and (P3b), respectively, to (P2b) and (P3b). Examples of such connection means include soldering and ultrasonic connection. As the feeding coaxial cable, a well-known high-frequency coaxial cable such as a fluororesin coating is preferably employed.

FIG. 3 shows another aspect of the present invention. The mode of FIG. 3A shows a mode in which the three ground plates 1c, 2c, and 3c are integrated into one sheet and the connection plates 1d and 2d are abolished. In this aspect, the ground plate area increases and more stable communication is possible. However, it is not suitable when the material cost is high or there are space restrictions.
Next, the mode of FIG. (3b) will be described. In this embodiment, the ground plate (3c) of the rightmost antenna (3) is replaced with a housing ground (3c) made of metal. When there is a housing ground near the antenna as in this aspect, it is possible to effectively use this and reduce the size of the entire antenna. In addition, in this figure, although the aspect which replaced the ground board (3c) of the rightmost antenna (3) with the metal housing | casing ground was shown, it does not necessarily need to be in this position, Replacement at any position is possible. Also, the number of antennas that can be replaced with the housing ground can be set to an arbitrary number depending on the situation.

A specific example of an antenna for an information terminal device that realizes a wide band of 2 GHz to 6 GHz is shown below.
First, a rectangular flat plate made of white and white having a length of 30 mm, a width of 30 mm, and a thickness of 0.1 mm was processed with an electric discharge machine to obtain an antenna element having the shape shown in FIG. At this time, the length of the LAN band low band element (1a) is 27.8 mm, the length of the Wi-Max band band element (1b) is 21.49 mm, and the LAN band high band element (1c) was 13 mm long and 2 mm wide.

The short-circuit plates (3a), (3b), and (3c) were all 7 mm high and 2 mm wide, and the distance (L) between adjacent antennas was 5 mm. The ground plates (4a), (4b), and (4c) were both 23 mm long and 23 mm wide.

Furthermore, feeding points (P1a) and (P2a) were set at a position 3 mm inward from the central end surface of the lowermost side. Also, the earth points (P1b) and (P2b) are respectively set at positions 3 mm inside from the upper end plate of the ground plate (4) facing the feeding points (P1a) and (P2a) on the ground plate (4). did. In this way, a small planar antenna element having an element plate height of 7 mm and a maximum width of 23 mm was completed.

Next, the antenna element described above was built in the information terminal device. At that time, in order to function as an antenna, a high-frequency coaxial cable covered with a fluororesin (PFA) having an outer diameter of 0.93 mm and a conductor diameter of 0.24 mm was used as the feeding coaxial cables (5a), (5b) and (5c). . At that time, the inner conductors (5a1), (5a2) and (5a3) of these cables were soldered to the feeding points (P1a), (P2a) and (P3a), respectively. Similarly, the outer conductors (5b1), (5b2), and (5b3) were soldered to the ground points (P1b), (P2b), and (P3b), respectively. Thus, a small composite antenna for information terminal equipment having a maximum height of 10 mm and a maximum width of 90 mm was obtained.

Finally, when the VSWR characteristics of this antenna were measured, the results shown in FIG. 4 were obtained. As is clear from this figure, in the antenna shown in this embodiment, the three antennas, that is, the elements (1a), (1b) and (1c) do not interfere with each other, ie, each band, The LAN band (low range: 2.4 GHz to 2.5 GHz, high range: 4.9 GHz to 5.875 GHz) shown in FIG. 4A and the Wi-Max band (2.3 GHz to 2) shown in FIG. .4 GHz, 2.5 GHz to 2.7 GHz, 3.3 GHz to 3.8 GHz) and resonate without causing interference with each other, and a sufficient bandwidth is secured in each band. I understand.

"Comparative example"
On the other hand, two independent antennas were obtained by vertically dividing the ground plate (4) of the above example into two equal parts. Next, one antenna was biased while being translated upward by 40 mm to obtain a composite antenna in which the short-circuit plates (3a) and (3b) were simply arranged non-target in the left-right direction. The composite antenna had a VSWR characteristic of 5 or more. This causes interference between the LAN band and the Wi-Max band, and a sufficient bandwidth is not secured in each band at the same time.

The above is an example of a planar composite antenna in which all the elements from the element to the ground plate are arranged on the same plane, but the present invention is not limited to this. For example, various modifications and applications are possible within the scope of the present invention, such as bending the element 90 degrees as required. Furthermore, in the above description, the LAN band and the Wi-Max band have been described. However, the present invention can cope with various changes such as a combination of other bands or a combination of Wi-Max bands. Further, the ground plate (4) may be divided in the longitudinal direction at the center thereof as long as the short-circuit plates (3a) and (3b) face each other with an interval of less than 10 mm.

The antenna of the present invention can be incorporated into information home appliances or automobile-related devices in addition to personal computers and various information terminal devices such as PDAs.

1, 2, 3 Individual antenna
1a, 2a, 3a Radiating element 1b, 2b, 3b Short-circuit plate 1c, 2c, 3c Ground plate 1d, 2d Connection portion 4a, 4b, 4c Feeding coaxial cable 4a1, 4b1, 4c1 Inner conductor 4a2, 4b2 of feeding coaxial cable 4c2 Outer conductors 4a2-1, 4a2-2, 4b-1 of the feeding coaxial cable Intermediate exposed external conductors P1a, P2a, P3a of the feeding coaxial cables 4a, 4b Feed points P1b, P2b, P3b Earth points Q1, Q2 Intermediate exposed outer conductor (4a2-1) and (4a2-2)
Ground plate connection point

Claims (5)

An antenna in which a radiating element is electrically connected to a ground plate via a short-circuit plate and is fed by a feeding coaxial cable, and has the following requirements a to c: .
a. As the radiating element, at least three or more antennas having different lengths are arranged in a line;
b. Each radiating element is connected to each ground plate via a respective short-circuit plate;
c. At least a part of each ground plate is connected by the outer conductor of the coaxial cable for power supply. The composite antenna according to claim 1, wherein each ground plate is connected to one body by a connection plate. The composite antenna according to claim 1, wherein a part of the ground plate is a housing ground. The composite cable according to claim 1 or 2, wherein at least one of the feeding coaxial cables is a coaxial cable having an intermediate strip process in which an outer conductor is peeled off and an outer conductor is exposed at at least one intermediate portion excluding a terminal. antenna. The composite antenna according to claim 1, wherein the feeding coaxial cable is disposed along an L-shaped connecting plate.

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