JP2007081848A - Parallel 2-wire antenna - Google Patents

Abstract

The present invention provides a parallel two-wire antenna capable of increasing the degree of freedom of adjusting means for widening the band and giving the conditions for wideband even in a limited space.
Plate conductors 2 and 3 arranged substantially in parallel are both long plate conductors, and slits 11 and 12 are formed respectively. In addition, short-circuit points 13 and 14 are provided in the flat conductors 2 and 3, respectively, in the vicinity of the center of the section where the slits 11 and 12 in the longitudinal direction are formed, and a short-circuit line 15 between them is short-circuited. Thereby, the freedom degree of the current pathway in the flat conductors 2 and 3 can be raised.
[Selection] Figure 1

Description

The present invention relates to a small parallel two-wire antenna used in a portable terminal or the like.

Antennas mounted on mobile phones have been reduced in size and weight, but needs for advanced functions and further miniaturization of mobile phones are expected to increase in the future. . In particular, the built-in antenna has a conflicting problem of downsizing and widening the band.

As a conventional small broadband antenna, there is a parallel two-wire antenna 101 as shown in FIG. 11 (Patent Document 1). The parallel two-wire antenna 101 has a structure in which one end of a parallel two-line 102 that is a radiation conductor is connected to a feeding end 103 and the other end is connected to a ground plane 104.

An antenna composed of two parallel lines operates in a wide band by superimposing two modes, a non-balanced mode and a balanced mode. When a sufficient space is allowed, the superposition of both modes can be controlled by the distance between two parallel lines. However, the conditions under which a wide band can be realized are quite limited, and some of the conditions for widening the band are lost when the antenna is downsized or brought close to the ground plane.

Therefore, conventionally, a method of adjusting the distance between two lines, the dielectric constant, and the like has been used to adjust the broadband condition between two parallel lines. Also, a method of adjusting using a matching circuit such as a duplexer, a multiplexer, and a balanced line has been proposed in order to correct the current distribution on the elements inside the antenna and operate in a wide band (Patent Document 2). ).
JP 2003-87043 A JP 2005-027184 A

However, the conventional method has the following problems.
The method of adjusting the broadband condition between two parallel lines by changing the distance between two lines, the dielectric constant, etc. is extremely low in a limited installation space. .

In addition, in the method of adjusting the current distribution using the matching circuit, the number of electronic components is increased, so that in addition to the problem of insertion loss due to circuit elements, there is a problem that the manufacturing process is complicated and the cost is increased.

In addition to this, in the case of multi-frequency sharing, it is very difficult to perform matching at the same time so as to obtain a wide band with two or more multi-frequency by using one set of matching circuits.

Accordingly, the present invention has been made to solve these problems, and provides a parallel two-wire antenna that can increase the degree of freedom of a broadband adjustment means and can provide a broadband condition even in a limited space. For the purpose.

According to a first aspect of the parallel two-wire antenna of the present invention, there is provided a small antenna that is provided in a portable device and includes two flat conductors arranged in parallel with each other and a dielectric or magnetic body. One or both of the flat conductors are provided with one or more slits, and a short-circuit portion for short-circuiting the flat conductors is provided in a range where the slits are formed when viewed in the longitudinal direction of the flat conductors. This is a parallel two-wire antenna.

In the second aspect, one or more linear conductor pieces are disposed between the two flat conductors so as to be substantially perpendicular to the flat conductor, and one end of the conductive piece is connected to one of the flat conductors. The parallel two-wire antenna is characterized in that the other end of the conductor piece is brought close to the other flat plate conductor.

According to a third aspect, the other flat conductor is processed so that the other end of the conductor piece is located on the same plane as the other flat conductor and does not contact the other flat conductor. A parallel two-wire antenna.

A fourth aspect is a parallel two-wire antenna characterized in that the other end of the conductor piece is in the slit provided in the other flat plate conductor.

A fifth aspect is a parallel two-wire antenna characterized in that the other end of the conductor piece includes a small flat plate provided substantially parallel to the other flat plate conductor.

In a sixth aspect, the slit provided in the other flat plate conductor is partially expanded in width at a position close to the other end of the conductor piece or the small flat plate. This is a two-wire antenna.

A seventh aspect is a parallel two-wire antenna characterized in that an interval between the other end or the small flat plate and the other flat plate conductor is substantially equal to a width of the slit.

As described above, according to the present invention, it is possible to provide a parallel two-wire antenna that satisfies a wide band condition in a limited space as compared with the prior art. Since the parallel two-wire antenna according to the present invention provides a means with a high degree of freedom for adjusting the band, it is possible to achieve a significantly wider band than the conventional one without using a matching circuit (about the conventional one). 5 times wider bandwidth).

In particular, a multi-frequency antenna having a plurality of resonance points on one path has conventionally been difficult to control independently in each frequency band. At the same time, it is possible to increase the bandwidth.

A configuration of a parallel two-wire antenna according to a preferred embodiment of the present invention will be described in detail with reference to the drawings. In addition, about each structural part which has the same function, the same code | symbol is attached | subjected and shown for simplification of illustration and description.

The parallel two-wire antenna of the present invention is a small antenna built in a portable device, and is an antenna that operates at a single frequency or two or more multi-frequency. FIG. 1 is a diagram showing a schematic configuration of a parallel two-wire antenna according to a first embodiment of the present invention.

As shown in FIG. 1A, in the parallel two-wire antenna 1 of this embodiment, the flat conductors 2 and 3 are arranged substantially in parallel. The flat conductor 2 forms a feed-side conductor pattern in which the feed end 4 is connected to a feed point (not shown), and the flat conductor 3 forms a ground-side conductor pattern in which the ground end 5 is connected to a ground point (not shown). is doing.

In this embodiment, the flat conductors 2 and 3 form a three-layer structure sandwiched between the dielectrics 6 and 7 and the dielectrics 7 and 8, respectively. 3 is arranged so as to be substantially perpendicular to the main plate 9. Thus, the parallel two-wire antenna 1 can be miniaturized by adopting a structure in which the flat conductors 2 and 3 are enclosed in the dielectrics 6, 7, and 8. However, the parallel two-wire antenna 1 of the present invention is not limited to this, and the flat conductors 2 and 3 may not be included in a dielectric.

The shape of the flat conductors 2 and 3 is shown in FIG. The flat conductors 2 and 3 are both long flat conductors, but are characterized in that slits 11 and 12 are formed respectively. Further, short circuit points 13 and 14 are provided in the flat conductors 2 and 3, respectively, in the vicinity of the center of the section where the slits 11 and 12 in the longitudinal direction are formed, and a short circuit 15 between them is short-circuited.

An example of a conventional parallel two-wire antenna is shown in FIG. Compared with the conventional parallel two-wire antenna shown in the figure, in the parallel two-wire antenna of the present invention, in addition to the slits 11 and 12, the position of the short-circuit point is different. In the conventional parallel two-wire antenna, the short-circuit points 13 and 14 are provided at the open ends of the flat conductors 2 and 3, whereas in the parallel two-wire antenna of the present invention, the slits 11 and 12 are formed. It is provided near the center of the longitudinal section.

By forming the slits 11 and 12 and the short-circuit points 13 and 14 as described above, the degree of freedom of the current path in the flat conductors 2 and 3 can be increased. That is, in the present embodiment, the conventional flat conductors 2 and 3 shown in FIG. 2 are each a single linear line, but in this embodiment, the slits 11 and 12 are formed, and the two through the slits in the same plane. Resonant systems in which a plurality of modes are mixed can be obtained by branching and flowing currents in one path.

As a result, two types of current paths are formed as the current path of the flat conductor 2, that is, a path from the feeding end 4 directly to the short-circuit point 13 and a path from the feeding end 4 through the open end 16 to the short-circuit point 13. Yes. Similarly, two different types of current paths are also formed in the flat conductor 3.

As described above, by increasing the degree of freedom of the current path in the flat conductors 2 and 3, the degree of freedom for widening the band is also increased. Conventionally, in order to increase the bandwidth, the distance and shape between the flat conductors 2 and 3, that is, the antenna size must be changed and adjusted. However, in the parallel two-wire antenna 1 of the present embodiment, the antenna size is changed. By adjusting the lengths and widths of the slits 11 and 12 and / or the positions of the short-circuit points 13 and 14 and the like without changing them, it is possible to easily increase the bandwidth.

As described above, according to the parallel two-wire antenna 1 of the present embodiment, it is possible to adjust so as to satisfy the broadband condition by greatly increasing the degree of freedom of the current path in a limited space. In the parallel two-wire antenna 1 of the present embodiment, it will be described below that the bandwidth is widened using the frequency locus on the Smith chart of FIG.

FIG. 3A is a plot of the input impedance (S11) of the conventional parallel two-wire antenna shown in FIG. 2 on the Smith chart, and FIG. 3B is a parallel two-wire type of this embodiment. 1 is an example of an antenna 1; On the Smith chart, it is shown that the reflection loss is lower as S11 is closer to the point 21 having an impedance of 50Ω located in the center of the figure, and the reflection loss increases as the distance from the center increases. In a resonance system such as an ordinary antenna, the frequency characteristic of S11 draws an arc on the Smith chart. When the frequency locus draws an arc around the origin of the Smith chart, there are many frequency points at which the reflection loss decreases. That is, it means operating in a wide band.

In the conventional miniaturized parallel two-wire antenna shown in FIG. 2, the frequency locus 22 draws a substantially circular locus away from the point 21 as shown in FIG. Since the substantially circular frequency locus 22 has a large diameter and its center is also shifted from the point 21 to the lower right of the drawing, it can be seen that the bandwidth is insufficient. Therefore, in the conventional parallel two-wire antenna, it is necessary to bring the center of the frequency locus 22 closer to the point 21 by using an adjustment circuit.

On the other hand, in the parallel two-wire antenna 1 of this embodiment shown in FIG. 3B, the diameter of the substantially circular locus drawn by the frequency locus 23 is small, and the center thereof is also close to the point 21. The center of the frequency locus 23 can be made closer to the point 21 by adjusting the length and width of the slits 11 and 12 and / or the positions of the short-circuit points 13 and 14.

In addition, although the flat conductors 2 and 3 of this embodiment shown in FIG.1 (b) shall form the slits 11 and 12 together, it is not necessary to form a slit in both flat conductors, and the broadband of an antenna Depending on the conversion conditions, a slit may be provided only in one of them. Further, the installation positions of the short-circuit points 13 and 14 can also be selected so that an appropriate broadband condition is obtained in the section where the slits in the longitudinal direction are formed.

FIG. 4 shows frequency characteristics of VSWR as another antenna characteristic of the parallel two-wire antenna 1 of the present embodiment. FIG. 4 shows that the frequency band where VSWR is 3 or less, for example, is about 0.3 GHz and is a wide band.

A second embodiment of the parallel two-wire antenna of the present invention will be described below with reference to FIG. FIG. 5 is a diagram showing a schematic configuration of a parallel two-wire antenna according to the second embodiment of the present invention.

Fig.5 (a) is a figure which shows the shape of the two flat conductors 31 and 32 of the parallel 2-wire type antenna of this embodiment. The flat conductor 31 of the present embodiment is formed in a straight line from the power feed end 33 to the open end 34, and further has a shape folded at the open end 34 so as to be substantially parallel thereto. As a feature of the flat conductor 31 of this embodiment, a slit 35 and a plurality of inter-line coupling adjusting elements 36 are further formed.

Similarly, the flat conductor 32 of the present embodiment is also formed in a straight line from the ground end 37 to the open end 38 and has a shape folded at the open end 38, and further has a slit 39 and a plurality of inter-line coupling adjusting elements 36. Is formed.

In the flat conductors 31 and 32 of the present embodiment, like the flat conductors 2 and 3 of the first embodiment, slits 35 and 39 are provided to increase the degree of freedom of the current path. In addition, the flat conductors 31 and 32 of this embodiment are characterized in that a plurality of inter-line coupling adjusting elements 36 are formed.

In the parallel two-wire antenna of the present embodiment, in addition to electromagnetic coupling between the flat conductors 31 and 32, electromagnetic coupling also occurs between the conductors sandwiching the slits 35 and 39 in each of the flat conductors 31 and 32. . At this time, three resonance points corresponding to the respective coupling appear in the input impedance characteristic. In general, electromagnetic field coupling strongly depends on the distance between elements. In this case, the electromagnetic field coupling sandwiching the slits 35 and 39 is stronger than the electromagnetic field coupling between the plate conductors 31 and 32. Therefore, 31 and 32 are isolated from each other, and it is not possible to achieve a wide band by superimposing the three modes.

Therefore, in this embodiment, by forming the line coupling adjusting element 36, the coupling amount between the conductors 31 and 32 and between the conductors sandwiching the slits 35 and 39 in the flat conductors 31 and 32 can be adjusted. The interline coupling adjusting element 36 will be described in detail with reference to FIG. FIG. 5B is an enlarged view of the interline coupling adjusting element 36.

The line coupling adjusting element 36 includes a connection end 36a, a proximity end 36b, and a short-circuit line 36c that short-circuits the connection end 36a and the proximity end 36b. The connection end 36a is formed so as to be connected to one flat conductor 31 or 32, and the proximity end 36b is formed close to the other flat conductor 32 or 31. In the embodiment of FIG. 5A, the flat conductors 31 and 32 are formed with two connection ends 36a and two adjacent ends 36b, respectively.

Two adjacent ends 36b formed on the flat conductor 31 are connected to the flat conductor 32 via a short-circuit line 36c and a connecting end 36a, respectively. Further, the proximity end 36 b is formed on the same plane as the flat conductor 31. That is, on the plane of the flat conductor 31, electromagnetic coupling across the slit 35 and equivalent capacitive coupling between the flat conductor 32 and the flat conductor 31 via the proximity end 36 b coexist.

The two adjacent ends 36b formed on the flat conductor 32 are the same as described above, and on the plane of the flat conductor 32, electromagnetic field coupling sandwiching the slit 39 and the flat conductor 31 via the adjacent ends 36b. And electromagnetic coupling between the flat conductors 32 occurs. As described above, by using the inter-line coupling adjusting element, various electromagnetic couplings can be provided between the four parallel conductor lines. By making effective use of all of the coupling mode in the plane conductor 31 plane, the coupling mode in the plane conductor 32 plane, and the coupling mode between the plane conductors 31 and 32, it is possible to realize a wider band.

In particular, by making the width 40 of each of the adjacent end 36b and the flat conductors 31 and 32 substantially equal to the width of the slits 35 and 39, the electromagnetic field coupling sandwiching the slit 35 or 39 and the line coupling adjusting element 36 are arranged. The amount of coupling between the flat conductors via can be made substantially equal. Further, by using a plurality of such line coupling adjustment elements, the degree of freedom of adjustment can be increased without changing the antenna size, and a wide band can be easily realized.

The widening of the bandwidth by superimposing a plurality of resonance modes will be described with reference to the frequency locus and VSWR example shown in FIG. The frequency trajectory shown in FIG. 6A is an example in which two loops 51 and 52 are formed in the vicinity of a point 21 having an impedance of 50Ω by combining three resonance modes.

Thus, by combining a plurality of resonance modes, when a loop can be formed around the point 21, a wideband frequency characteristic as shown in FIG. 6B can be realized. From FIG. 6B, it can be seen that the band in which the VSWR is, for example, 3 or less is greatly expanded.

In the parallel two-wire antenna according to the second embodiment of the present invention shown in FIG. 5, as described above, the degree of freedom of the means for adjusting the broadband is greatly increased by providing the line coupling adjusting element 36. It was. That is, it is possible to adjust a plurality of generated resonance modes by adjusting the connection state such as the number and position of the line coupling adjusting elements 36.

In the present embodiment, the frequency trajectory and VSWR before adjusting the connection state such as the number and position of the line coupling adjusting elements 36 are shown in FIGS. 7A and 7B, and the connection state is adjusted to adjust the broadband. FIGS. 7 (bc) and 7 (d) show the frequency trajectory and VSWR when the conversion is achieved. From the figure, it can be seen that the parallel two-wire antenna according to the present embodiment can easily realize a wide band by discretely selecting the combination of the connection states of the inter-line coupling adjustment element 36.

In the second embodiment of the present invention shown in FIG. 5, each of the flat conductors 31 and 32 has two short-circuit points 41 and 42, respectively. The short-circuit point is an important factor that gives broadband conditions. In the case of a dual frequency antenna, the short-circuit point far from the feed point mainly affects the impedance characteristics on the low frequency side, and the short-circuit point near the feed point mainly affects the impedance characteristics on the high frequency side. . Therefore, by providing a plurality of short-circuit points 41 and 42, a wide band can be realized over multiple frequencies. FIG. 8 shows an example of VSWR when a dual-frequency antenna is realized in this embodiment. Even when the parallel two-wire antenna of the present embodiment is used for a multi-frequency shared antenna as described above, by providing the inter-line coupling adjustment element 36, it is possible to easily realize a wide band at each use frequency.

In the inter-line coupling adjusting element 36 shown enlarged in FIG. 5B, the proximity end 36 b is formed by a small flat plate provided substantially parallel to the flat plate conductor 31 or 32. Further, in order to arrange the proximity end 36b on the same plane as the flat conductor 31 or 32, the width of the portion where the proximity end 36b of the slit 35 or 39 is disposed is enlarged, and the proximity end 36 and the flat conductor 31 or 32 are In close proximity with a predetermined width.

FIG. 9 shows still another embodiment of the parallel two-wire antenna of the present invention. FIG. 9A shows a perspective view, and FIG. 9B shows a cross-sectional view. In the present embodiment, one or more linear conductor pieces 63 disposed between the two flat conductors 61 and 62 so as to be substantially perpendicular to the two flat conductors are provided.

In FIG. 9, one end of the conductor piece 63 is connected to the flat conductor 61, and the other end of the conductor piece 63 is brought close to the flat conductor 62. As a result, capacitive coupling occurs between the other end of the conductor piece 63 connected to the flat conductor 61 and the flat conductor 62, so that the number and position of the conductor pieces 63, the other end of the conductor piece 63 and By adjusting the distance between the flat conductor 62 and the like, it is possible to give a broadband condition.

In FIG. 9, the conductor piece 63 is connected to the flat conductor 61, but may be connected to the flat conductor 62. In this case, the one end of the conductor piece 63 and the flat conductor 61 are brought close to each other at a predetermined interval.

FIG. 10 shows still another embodiment of the parallel two-wire antenna of the present invention. In the present embodiment, the other end of the conductor piece 63 shown in FIG. 9 is positioned on the same plane as the front plate conductor 62 and is not in contact with the plate conductor 62.

In FIG. 10A, the flat conductor 62 is provided with a notch so that the other end of the conductor piece 63 does not contact the flat conductor 62. In FIG. 10B, the other end of the conductor piece 63 is disposed in a slit 64 provided in the flat conductor 62 and is provided so as not to contact the flat conductor 62.

According to the present embodiment, capacitive coupling between the other end of the conductor piece 63 and the flat conductor 62 is generated in the plane of the flat conductor 62, and it is possible to achieve a wide band by adjusting this.

As described above, the parallel two-wire antenna according to the present invention provides a means with a high degree of freedom for adjusting the band, so that it is easy to achieve a wider band than before without using a matching circuit. . Moreover, even when applied to a multi-frequency antenna, it is possible to simultaneously increase the bandwidth in a plurality of frequency bands.

Such a structure can be easily realized by performing etching and through-hole plating on a general double-sided copper-clad plate. In addition, it is possible to significantly reduce the size by encapsulating a material formed by etching and through-hole plating with a dielectric having a higher relative dielectric constant.

In the above embodiment, only the antenna provided with the parallel conductor and the dielectric material is described. However, the same effect can be obtained when a magnetic material is used instead of the dielectric material.

FIG. 1 is a diagram showing a schematic configuration of a parallel two-wire antenna according to a first embodiment of the present invention. FIG. 1A is an overall configuration diagram of a parallel two-wire antenna 1 according to the present embodiment, and FIG. 2B is a diagram illustrating a detailed shape of the flat conductors 2 and 3. FIG. 2 is a diagram illustrating an example of a conventional parallel two-wire antenna. FIG. 3 is a graph showing an example of a frequency locus of a parallel two-wire antenna. FIG. 3A shows an example of the frequency trajectory of a conventional parallel two-wire antenna, and FIG. 3B shows an example of the frequency trajectory of the parallel two-wire antenna 1 of the present invention. FIG. 4 is a graph showing the VSWR frequency characteristics of the parallel two-wire antenna 1 of the present invention. FIG. 5 is a diagram showing a schematic configuration of a parallel two-wire antenna according to the second embodiment of the present invention. FIG. 5A is a diagram showing the shapes of two flat conductors, and FIG. 5B is an enlarged view of the interline coupling adjusting element 36. FIG. 6 is a conceptual diagram of widening the band by combining three resonance modes. 6A shows the frequency locus of S11 on the Smith chart, and FIG. 6B shows the VSWR frequency characteristic. FIG. 7 is a graph showing an example of the frequency trajectory and the VSWR in the second embodiment of the present invention. 7A shows the frequency trajectory before adjustment, FIG. 7B shows the VSWR before adjustment, FIG. 7C shows the frequency trajectory after adjustment, and FIG. 7D shows the VSWR after adjustment. Each is shown. FIG. 8 shows an example of the VSWR when the second embodiment of the present invention is a dual-frequency antenna. FIG. 9 is a schematic view showing still another embodiment of the parallel two-wire antenna of the present invention. FIG. 9A shows a perspective view, and FIG. 9B shows a cross-sectional view. FIG. 10 is a schematic view showing still another embodiment of the parallel two-wire antenna of the present invention. FIG. 10A is an example in which a notch is provided in the flat conductor 62, and FIG. 10B is an example in which the other end of the conductor piece 63 is disposed in the slit 64. FIG. 11 is a schematic diagram showing a parallel two-wire antenna, which is a conventional small broadband antenna.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Parallel 2-wire type antenna 2, 3, 31, 32, 61, 62 ... Flat conductor 4, 33 ... Feeding end 5, 37 ... Grounding end 6, 7, 8 ... Dielectric Body 9 ... Ground plate 11, 12, 35, 39, 64 ... Slit 13, 14 ... Short-circuiting point 15 ... Short-circuit wire 16, 17, 34, 38 ... Open end 21 ... Frequency Center point of the locus (impedance 50Ω point)
22, 23 ... Frequency trajectories 31, 32 ... Flat conductor 36 ... Interline coupling adjustment element 36a ... Connection end 36b ... Proximity end 40 ... Width 41 between the proximity end and the flat conductor 42 ... Short-circuit points 51, 52 ... Frequency locus loop 63 ... Conductor piece

Claims (7)

A small antenna built in a portable device having two flat conductors arranged in parallel and a dielectric or magnetic body,
One or more slits are provided in one or both of the two flat conductors,
A parallel two-wire antenna, characterized in that a short-circuit portion for short-circuiting the two flat conductors is provided in a range where the slit is formed when viewed in the longitudinal direction of the flat conductor. One or more linear conductor pieces arranged between the two flat conductors so as to be substantially perpendicular to the flat conductor,
The parallel two-wire antenna according to claim 1, wherein one end of the conductor piece is connected to one of the flat plate conductors, and the other end of the conductor piece is brought close to the other flat plate conductor. The other flat plate conductor is processed so that the other end of the conductor piece is on the same plane as the other flat plate conductor and does not contact the other flat plate conductor. The parallel two-wire antenna according to claim 2. 4. The parallel two-wire antenna according to claim 2, wherein the other end of the conductor piece is in the slit provided in the other flat plate conductor. 5. 5. The parallel two-wire antenna according to claim 2, wherein the other end of the conductor piece includes a small flat plate provided substantially parallel to the other flat plate conductor. 6. . 6. The slit provided in the other flat plate conductor is partially expanded in width at a position close to the other end of the conductor piece or the small flat plate. The parallel two-wire antenna described in 1. The parallel two-wire antenna according to claim 6, wherein a distance between the other end or the small flat plate and the other flat plate conductor is substantially equal to a width of the slit.

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