JP4507507B2 - Multi-frequency antenna - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a multi-frequency small slot antenna or a multi-frequency slot antenna for a wireless LAN incorporated in an information terminal device such as a personal computer, a PDA (portable information device), a mobile phone, or a VICS.
[0002]
[Prior art]
In recent years, in a PDA or the like equipped with a wireless LAN or Bluetooth (short-range wireless data communication system), in order to reduce the size of the antenna, not only widening of the use radio frequency band but also multi-frequency has become popular. .
As an example, an inverted-F multi-frequency antenna that can handle three or more frequencies has been proposed (see, for example, Patent Document 1).
However, in this proposal, the resonance frequency band the number of radiation electrodes corresponding to the number (unit radiation conductor) group, ground (GND) plate, because it requires at least three components, such as 及 beauty short circuit plate, multifrequency Then, there is a problem that the size and space are inevitably increased. On the other hand, if the distance between the radiation electrodes is made too narrow in order to reduce the space, there is a problem in communication quality that interference easily occurs, and there is a limit to downsizing. Furthermore, since the radiation electrode is a thin metal plate in the form of a slice with low strength, it can be bent by a minor work mistake when attaching a feeder such as a coaxial cable, resulting in deterioration of the antenna characteristics. There was also a problem of letting it go.
On the other hand, a single-frequency receiving slot antenna has been proposed in which a single slot is disposed as a radiation electrode on a single metal plate. Since this antenna has a simplified structure and solves the above-described strength problem, it has recently been attracting attention (see, for example, Patent Document 2).
However, in this document, there is no disclosure about the antenna structure for a multi-frequency, let alone to minimize VSWR over a multi-frequency in a multi-frequency antenna, the required properties such as improved improved and the reception sensitivity of the transmission and reception characteristics (Gain) There is no recognition of measures to satisfy them.
[0003]
[Patent Document 1]
JP 2000-68736 A [Patent Document 2]
Japanese Patent Laid-Open No. 2002-84128
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a multi-frequency slot antenna or a multi-frequency slot antenna for wireless LAN that supports two or more frequencies incorporated in an information terminal device such as a personal computer or a PDA over multiple frequencies. voltage standing wave ratio (VSWR) is small, is to provide a multi-frequency antenna miniaturization is realized with excellent transmission and reception characteristics and reception sensitivity.
[0005]
[Means for Solving the Problems]
In the antenna in which a plurality of linear slots of which both ends are closed are juxtaposed on a conductive substrate, the inventors of the present invention have the longitudinal direction of the linear slot corresponding to the lowest or highest frequency. When an imaginary line perpendicular to a linear slot that passes through the eccentric feeding point and is closed at both ends is drawn, a point where the VSWR of the cut is the smallest at the outer peripheral portion is drawn. By arranging these slots along a line under specific conditions, the above-mentioned problems have been solved.
[0006]
Thus, according to the present invention, a multi-frequency antenna characterized by having the following requirements A to D is provided.
A. A plurality of linear slots having both ends closed on the conductive base material are arranged in a juxtaposed state as a radiating electrode group, thereby imparting an operation function of two or more frequencies;
B. Among the plurality of linear slots closed at both ends, the outer peripheral portion in the longitudinal direction of the slot corresponding to the lowest or highest frequency (excluding the outer peripheral portion corresponding to the midpoint in the longitudinal direction) A point where the voltage standing wave ratio (VSWR) of the slot is the minimum or the vicinity thereof as an eccentric feed point, and the inner conductor of the high-frequency coaxial cable connected to the point; and
C. When drawing an imaginary line that passes through the eccentric feed point and is orthogonal to the linear slot that is closed at both ends , these slits are formed with a slot length (a ) And the slot length (b) on the other side are in a similar arrangement in a range of a: b = 1: 1.5 to 1: 4.5.
D. The outer conductor of the high-frequency coaxial cable is connected to a ground point provided on the side opposite to the feeding point across the plurality of linear slots closed at both ends .
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with reference to an example of an antenna corresponding to two frequencies.
FIG. 1 shows an antenna element in which two linear slots of different lengths are closed as a radiating electrode group (hereinafter, this “linear slot” is simply abbreviated as “slot”). FIG.
FIG. 2 is a plan view showing an example in which the antenna element shown in FIG. 1 is applied to an information terminal device built-in multi-frequency antenna.
1 to 2, (1) is a flat conductive base material, (2) is a first slot formed by cutting out a part of the conductive base material (1) (corresponding to the first frequency) Similarly, the first radiation electrode), (3) is formed by cutting out a part of the conductive substrate (1) so as to be shorter than the length of the slot (2). (Second radiation electrode corresponding to frequency), (4) is a high-frequency coaxial cable, (4a) is its inner conductor, (4b) is its outer conductor, (5) is a mounting hole for the conductive substrate (1), ( G) is an earth point, (M) is an eccentric feeding point, (P) is an imaginary line passing through the eccentric feeding point and orthogonal to the slot group, (L1) is the length (full length) of the slot (2), (L2) Is the length (total length) of slot (3), (W) is the width of slots (2) and (3), (D) is next to slot (2) and slot (3) The contact interval, and (C) is the midpoint of each slot. For the convenience of explanation, the slot length (a) on one side divided by the virtual line (P) is indicated by a1 for the slot length (2) and a2 for the slot (3). It was. Similarly, regarding the slot length (b) on the other side divided by the virtual line (P), the slot length of the slot (2) is indicated by b1, and the length of the slot (3) is indicated by b2.
[0008]
What is characteristic of the present invention is that a: b (in FIG. 1, a1: b1 ) , as specified in requirement C in relation to the position of the eccentric feed point (M) , slots (2), (3) . A2: b2) = 1: 1.5 to 1: 4.5. As a result, as shown in Table 1 below , the VSWR in the vicinity of a plurality of resonance points as the entire antenna element is kept to the minimum, the transmission / reception characteristics are improved, and the reception sensitivity (Gain) of the antenna is remarkably improved. Can be improved .
These points will be described in more detail with reference to FIG.
First, of the slot (2) and the slot (3) arranged in the juxtaposed state, the position where the VSWR of the slot is the minimum or the vicinity thereof (M) is set as the eccentric feeding point on the outer periphery of the slot (2). . Then, when an imaginary line (P) passing through the eccentric feed point (M) and orthogonal to the slots (2) and (3) is drawn, the slot (2) and the imaginary line (P) are drawn along the imaginary line (P). (3) is arranged in a similar manner with the above-mentioned a: b ratio (requirement C) .
As described above, the eccentric feed point (M) is set at or near the position where the VSWR of the slot (2) or (3) is minimum on the outer periphery of the slot (2) or (3). The amount of eccentricity in this case is 0 in the second quadrant of the X and Y coordinate axes with the midpoint (C) in the longitudinal direction of the slot (2) as 0, or the midpoint (C) in the longitudinal direction of the slot (3) as 0. In the first quadrant of the X and Y coordinate axes as points, it is preferable that both the X axis direction and the Y axis direction are in the range of 20% to 40%. Further , regarding other requirements of the slot, the length (L1) of the slot (2) is appropriately selected from the range of 35 to 45 mm, and the length (L2) of the slot (3) is appropriately selected from the range of 63 to 73 mm. The width (W) of each slot at this time may be appropriately selected from the range of 0.5 mm to 5 mm. Further, if the adjacent distance (D) between the slot (2) and the slot (3) is too small, interference occurs. Conversely, if the distance (D) is too large, the space efficiency is deteriorated. Considering this, it is preferable that the adjacent interval (D) is in a range of 0.5 mm to 10 mm.
Furthermore, since the slot disposed in the conductive base material (1) is multi-frequency reception, a plurality, usually two or three, corresponding to the number of resonance frequency bands are disposed. As the conductive substrate at this time, a conductive metal substrate such as white (brass), copper, iron, or brass is preferable. Among them, western white (white copper) is particularly preferable because it is excellent in strength, workability, and corrosion resistance. The shape of the substrate is usually a flat plate as shown in the figure. A typical example of this “flat plate” is a metal plate. At that time, in order to ensure stable operation, the metal plate needs to have an area of at least 70 mm 2 or more. Practically, it is desirable to set it in the range of 140 mm2 to 420 mm2. Moreover, although there is no special restriction | limiting about the thickness, what is necessary is just to select suitably in the range of 0.3 mm-3 mm in consideration of intensity | strength. Moreover, as a conductive base material, the flat metal substrate which provided the electroconductive part, such as the metal vapor deposition film which vapor-deposited the metal on the resin film other than the metal mentioned above, or copper foil may be sufficient. And about these base materials, you may form a slot by an etching other than a notch | incision.
As described above, the antenna element has been described with reference to FIG. 1. When actually constructing a multi-frequency antenna from the element, the eccentric feed point (M) and the slots (2) and (3) are sandwiched as shown in FIG. An earth point (G) is provided on the opposite side. This earth point (G) is in the X-axis direction and the Y-axis in the fourth quadrant of the X and Y coordinate axes on or near the virtual line (P) or in the slot (3) midpoint (C). What is necessary is just to provide in the location eccentrically 0-20% in the direction. Then, these eccentric feed point (M) and ground point (G), may be connected to the feeding member such as a high-frequency coaxial cable (4). At this time, the inner conductor (4a) of the high-frequency coaxial cable (4) is connected to the eccentric feeding point (M), and the outer conductor (4b) is connected to the ground point (G). As the high-frequency coaxial cable (4), a well-known high-frequency coaxial cable such as a fluororesin coating is employed. In order to connect the high-frequency coaxial cable (4) to the eccentric feeding point (M) and the earth point (G), soldering or ultrasonic connection may be used.
Finally, when the antenna of the present invention is attached to the information terminal device, it can be easily attached by utilizing the attachment hole (5).
[0009]
A specific example of an antenna for an information terminal device to which a multi-frequency element corresponding to the two frequencies shown in FIG. 1 is applied will be shown below.
First, a slot having a length of 68 mm and a width of 1 mm corresponding to the 2.45 GHz band by a simple press machine at the center of a flat conductive substrate (1) made of a white plate of 70 mm length, 50 mm width and 0.4 mm thickness. (2) was formed to puncture only by the first radiation electrode. At this time, the position of the eccentric feed point (M) at which the VSWR of the slot (2) is the minimum is X in the second quadrant of the X and Y coordinate axes with the midpoint (C) of the slot (2) being zero. The location was 15% eccentric in the axial direction and 30% both in the Y-axis direction. Therefore, in the slot (2) divided by the virtual line (P) passing through the eccentric feeding point (M) of the slot (2) and orthogonal to the slots (2) and (3) , the slot length (a1 on one side ) ) And the slot length (b1) on the other side are 19 mm (a1) and 49 mm (b1), respectively, and a1: b1 = 1: 2.58.
Next, as shown in FIG. 1, on the right side of the slot (2), as a second radiation electrode corresponding to the 5.25 GHz band, the slot (3) having a length (L2) of 40 mm and a width (W) of 1 mm. Were juxtaposed with an adjacent spacing (D) of 1 mm. At this time, in the slot (3) divided by the virtual line (P), the slot length (a2) on one side and the slot length (b2) on the other side are 11.4 mm (a2) and 28. 6 mm (b2), and a2 : b2 = 1: 2.50 . In this way, both slots (2) and (3) were placed side by side along the virtual line (P) in a similar manner. Further, as shown in FIG. 2, in the fourth quadrant of the X and Y coordinate axes with the midpoint (C) of the slot (3) as the zero point, both the X axis direction and the Y axis direction are 15% eccentric. An earth point (G) was provided.
Finally, the inner conductor (4a) and outer conductor (of the fluororesin (PFA) coaxial cable (4) having an outer diameter of 0.93 mm and a conductor diameter of 0.24 mm are connected to the feeding point (M) and the earth point (G). By connecting each of 4b) with solder, an information terminal device built-in antenna corresponding to two frequencies was obtained.
Hereinafter, the effects of the present invention will be described in Table 1 in comparison with the conventional example (comparative example).
In this embodiment, in each slot divided by the virtual line (P), the ratio of the slot length (a) on one side to the slot length (b) on the other side is a: b = 1: 2. 5, Comparative Example 1 shows the case of a: b = 1: 5 ( when the upper limit of the present invention, a: b = 1: 4.5) , and Comparative Example 2 shows the case of a: b = 1: 1 (the lower limit of the present invention, a: b = 1: less than 1.5). The other conditions such as frequency in the comparative example were the same as those in the present invention.
[Table 1]
As can be seen from Table 1 above, when the requirement C of the present invention is satisfied , a highly efficient antenna having a small VSWR over a plurality of frequencies (first frequency and second frequency), excellent transmission and reception characteristics, and improved even to Gain. It can be seen that
Such an antenna can be incorporated into various information terminal devices such as personal computers, PDAs, and the like, as well as home appliances or automobile-related devices. Of course, it goes without saying that various modifications and applications are possible within the scope of the idea of the present invention.
[0010]
【The invention's effect】
According to the present invention, VSWR as compared with conventional small transmission and reception characteristics and Gain greatly improved, moreover there is provided a multi-frequency antenna miniaturization is realized, the antenna information terminal equipment built such as a personal computer As a result, it has a particularly remarkable effect of exerting its functions.
[Brief description of the drawings]
FIG. 1 is a plan view of an antenna element in which two linear slots having opposite ends are arranged side by side as a radiation electrode group in the antenna of the present invention corresponding to two frequencies.
FIG. 2 is a plan view showing an example in which the antenna element of the present invention shown in FIG. 1 is applied to a multi-frequency antenna for incorporating information terminal equipment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Conductive base material 2 Slot which forms 1st radiation electrode 3 Slot which forms 2nd radiation electrode 4 High frequency coaxial cable 4a Inner conductor 4b of high frequency coaxial cable (4) Outer conductor 5 of high frequency coaxial cable (4) Mounting hole G Ground point M Eccentric feed point P One side of slot (2) divided by imaginary line a1 imaginary line (P) passing through eccentric feed point (M) and orthogonal to slot groups (2) and (3) Slot length b1 Slot length a2 on the other side of slot (2) divided by virtual line (P) a2 Slot length b2 on one side of slot (3) divided by virtual line (P) Virtual line (P) Slot L1 on the other side of slot (3) divided by the length of slot (2) L2 length of slot (3) W width of slot (2), (3) slot C (2), (3) Midpoint D Slot (2) and Adjacent distance to slot (3)

Claims (1)

A multi-frequency antenna comprising the following requirements A to D:
A. A plurality of linear slots having both ends closed on the conductive base material are arranged in a juxtaposed state as a radiating electrode group, thereby imparting an operation function of two or more frequencies;
B. Among the plurality of linear slots closed at both ends, the outer peripheral portion in the longitudinal direction of the slot corresponding to the lowest or highest frequency (excluding the outer peripheral portion corresponding to the midpoint in the longitudinal direction) A point where the voltage standing wave ratio (VSWR) of the slot is the minimum or the vicinity thereof as an eccentric feed point, and the inner conductor of the high-frequency coaxial cable connected to the point; and
C. When drawing an imaginary line that passes through the eccentric feed point and is orthogonal to the linear slot that is closed at both ends , these slits are formed with a slot length (a ) And the slot length (b) on the other side are in a similar arrangement in a range of a: b = 1: 1.5 to 1: 4.5.
D. The outer conductor of the high-frequency coaxial cable is connected to a ground point provided on the side opposite to the feeding point across the plurality of linear slots closed at both ends .