JP2001085927A - Antenna unit and communication area extension method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a technique that extends an antenna communication area while avoiding deterioration in reception sensitivity depending on a reception position. SOLUTION: A capacitor 5b is connected to a coil 5a placed between two loop antennas 3, 4 to form a closed loop circuit (resonance circuit) 5. The circuit 5 is electromagnetically coupled with the antennas 3, 4 and the magnetic flux formed by them interlinks an area surrounded by a profile of the circuit 5. Thus, when the antennas 3, 4 are fed in phase, the closed loop circuit 5 acts like a loop antenna to produce a large amount 5b magnetic flux between the antennas 3, 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for expanding an area (communication area) in which communication can be performed with an antenna while avoiding a decrease in reception sensitivity due to a reception position.

[0002]

2. Description of the Related Art In recent years, non-contact type IC cards incorporating a CPU in addition to a memory have been commercialized. The IC card is a freely portable medium capable of managing various information, and has high versatility. Because of its versatility,
It is expected that it will be used in various fields and spread widely in society in the future. In fact, some companies have their IC
In some cases, personal information of employees is stored on a card, and the card is equipped with an in-house security function, a health check data management function, an electronic money function, and the like. Some recreational facilities use the gate system.
Many demonstration tests for full-scale operation have been conducted.

The above-mentioned IC card communicates with an IC card device such as a reader / writer via an antenna provided in the IC card, and also obtains operating power from the antenna. Therefore, in order to operate it, it must be moved into the communication area of the IC card device.

[0004] The IC card is often used so as to be held over an IC card device, taking advantage of its non-contact type. Such an IC card device that uses an IC card usually indicates a range (communication area) where the IC card should be held over for communication. Most IC card devices employ a directional antenna such as a loop antenna so that communication with the held IC card can be selectively performed.

[0005]

An IC card device is an I-card device.
The communication area (communication area) with the C card needs to be widened to some extent in order to improve the usability of the IC card. Conventionally, the area has been expanded as follows.

[0006] In a loop antenna used in most IC card devices, a magnetic flux is generated in a range (plane) surrounded by a line forming the loop antenna. For this reason, the communication area can be expanded by enlarging the area of the range (surface) surrounded by the line. However, if the area is increased to some extent, the magnetic flux is distributed concentrically around the line, that is, a large amount is generated in the vicinity of the line. However, there is a problem that an area where communication with an IC card cannot be performed (an area having poor reception sensitivity; hereinafter, conveniently referred to as a low sensitivity area) occurs.

[0007] If there is a low sensitivity area in the communication area, it is likely that communication with the IC card device is not performed even though the user holds the IC card over the communication area. If the communication is not performed, the user holds the IC card over the communication area again.
If the communication is not repeatedly performed, the user takes measures such as calling a clerk. They are very undesirable because they cause a significant hindrance to the smooth operation of the IC card. For this reason, there is a limit to the expansion of the communication area by manipulating the area of the surface of the loop antenna, and it cannot be made too large.

If the area of the surface of the loop antenna is made too large compared to the antenna of the IC card, the above problem occurs. For this reason, conventionally, as shown in FIG. 9, the communication area is often expanded by combining (arranging) a plurality of loop antennas 71 each having a reduced area. 9A shows a case where two loop antennas 71 are arranged horizontally, FIG. 9B shows a case where two loop antennas 71 are arranged vertically, and FIG. 9C shows a case where four loop antennas 71 are arranged vertically and horizontally. (The vertical and horizontal lines are arranged in two columns).

When a plurality of loop antennas 71 are arranged, unless the distance between the antennas 71 is increased, magnetic fluxes between adjacent antennas 71 interfere with each other and cancel each other, thereby creating a low sensitivity area. However, when the distance is increased, the magnetic flux between them is reduced, so that a low-sensitivity area also occurs.

FIG. 10 is a diagram for explaining a magnetic field generated when the distance between loop antennas is increased. FIG.
0 (a) is a front view and FIG. 2 (b) is a top view. In FIG. 4, 81 indicates a magnetic field, and 82 indicates an antenna mounted on the IC card.

The distance between the two loop antennas 7 is increased.
When 1 is arranged, as shown in FIG. 10, the magnetic flux penetrating the antenna 82 between them decreases. Therefore, IC
Even if the card is brought close to the communication area, the communication IC of the IC card cannot receive power required for operation from the antenna 82.

[0012] As described above, a low-sensitivity area has been present in the communication area to some extent, which has hindered the smooth operation of the IC card. The IC card will be widely used in society in the future. For this reason, it has been strongly desired that the communication area can be expanded while avoiding the generation of a low-sensitivity area, particularly in a field where an IC card is used or will be used in the future.

[0013] It is an object of the present invention to provide a technique capable of expanding a communication area of an antenna while avoiding a decrease in receiving sensitivity due to a receiving position.

[0014]

SUMMARY OF THE INVENTION An antenna unit according to the present invention includes at least one antenna that is supplied with power and generates a magnetic flux, and at least one closed loop circuit that is electromagnetically coupled to the antenna.

In the above configuration, it is desirable that the closed loop circuit is a resonance circuit formed by connecting a coil and a capacitor. Preferably, the closed loop circuit is arranged such that the plane formed by the lines of the circuit is parallel to the plane of the antenna. The circuit surface may be at a position other than the plane including the antenna surface. Or,
Preferably, the closed loop circuit is arranged such that the normal to the plane formed by the lines of the circuit intersects the normal to the plane of the antenna.

The communication area expanding method of the present invention is premised on being used for expanding an area where communication can be performed by an antenna. At least one closed loop circuit is arranged at a position electromagnetically coupled to the antenna. The area is expanded by operating the circuit as an antenna.

According to the present invention, a closed loop circuit is disposed at a position where it is electromagnetically coupled to the antenna, and a magnetic field generated in the antenna generates a magnetic field in the closed loop circuit. As a result, the closed loop circuit behaves like an antenna, and magnetic fluxes not used for communication among magnetic fluxes generated by the antenna are collected by the closed loop circuit and can be used for communication. For this reason, the communication area can be expanded while avoiding the generation of an area (low-sensitivity area) where the magnetic flux density is significantly lower than the others.

For example, if a closed loop circuit is arranged between two antennas, it will complement the magnetic flux to be generated between them. From this, even when a plurality of antennas are arranged, by arranging a closed loop circuit between the antennas, it is possible to expand a communication area while avoiding generation of a low-sensitivity area.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. <First Embodiment> FIG. 1 is a diagram illustrating the configuration of an antenna unit according to a first embodiment.

The unit 1 is mounted on, for example, an apparatus for communicating with an IC card held by a user. As shown in FIG. 1, an antenna substrate 2 and loop antennas 3 and 4 on which a wire is printed several turns are provided.
And a coil 5a in which a wire is printed several turns between the antennas 3 and 4, and a capacitor 5b connected to the coil 5a.

A driver 7 is connected to each of the loop antennas 3 and 4. Those drivers 7
Is a signal from the oscillator 8 (the carrier wave (oscillator 8
A signal obtained by modulating the signal output by itself) is amplified and fed to the loop antenna 3 or 4 in the same phase.

Next, the operation of each part constituting the antenna unit 1 will be described. By connecting the coil 5a and the capacitor 5b, they form a closed loop circuit (resonant circuit) 5. By disposing the coil 5a between the loop antennas 3 and 4, the loop antenna 3
The closed loop circuit 5 is electromagnetically coupled to the loop antennas 3 and 4 while increasing the distance between the loop antennas 3 and 4 to avoid interference of the magnetic flux generated by them. The vertical width of the coil 5a (length on a line orthogonal to the shortest line connecting the antennas 3 and 4 on the antenna substrate 2) is different from that of the antennas 3 and 4 in order to more strongly electromagnetically couple. Are matched.

FIG. 2 is a diagram for explaining a magnetic field generated by the antenna unit 1. FIG. 2A is a front view (a view when the unit 1 is viewed from the front direction (a direction parallel to a perpendicular line of the surfaces of the loop antennas 3 and 4)), and FIG. 4 is a view when viewed from a vertical direction orthogonal to a perpendicular to the surface of No. 4). In FIG. 2, reference numeral 10 denotes an antenna mounted on the IC card, and the magnetic field is indicated by a broken line.

In the closed loop circuit 5 to which power is not supplied, a part of the magnetic flux generated in the loop antennas 3 and 4 to which it is electromagnetically coupled penetrates (links). When power is supplied to the loop antennas 3 and 4 in the same phase, the magnetic fluxes generated therefrom do not interfere so as to cancel each other, and the closed loop circuit 5
(In the area surrounded by the line forming the coil 5a). For this reason, a current flows through the closed loop circuit 5 so as to cancel the interlinking magnetic flux, and a new magnetic flux is generated. As a result, the closed loop circuit 5 behaves like a loop antenna arranged between the loop antennas 3 and 4 and operating in phase with them. Among the magnetic fluxes generated by the loop antennas 3 and 4, magnetic fluxes that cannot be used for communication are collected by the closed loop circuit 5 and reused for communication. As a result, as shown in FIG.
Also, a large amount of magnetic flux is generated between and.

By providing the closed loop circuit 5 on the flat surface of the antenna substrate 2, as shown in FIG. 2B, the surface formed by the coil 5 a of the circuit 5 And 4 are parallel to each other (here, the surfaces are provided so as to be on the same plane). Thus, the closed loop circuit 5 has the same directional characteristics as the loop antennas 3 and 4 with respect to the antenna substrate 2. For this reason, the magnetic flux generated in the closed loop circuit 5 efficiently reaches the low sensitivity area in the communication area generated mainly by the loop antennas 3 and 4 alone. In this way, the receiving sensitivity in the communication area is made more uniform and the magnetic flux density is made higher.

The closed loop circuit 5 forms a resonance circuit by connecting a capacitor 5b to a coil 5a through which magnetic flux passes. By using it as a resonance circuit, the reactance of the entire circuit 5 can be further reduced. In the present embodiment, this is used to make the current flowing by the magnetic flux passing through the closed loop circuit 5 larger. In order to maximize the number of magnetic fluxes passing through the closed loop circuit 5, in the present embodiment, the resonance frequency thereof is made to match the frequency of the carrier output from the oscillator 8.

For these reasons, communication can be performed no matter how the antenna 11 of the IC card is brought close to the antenna unit 1. Also, regardless of the positional relationship between the IC card and the antenna unit 1, the distance from the antenna unit 1 with which the IC card can communicate is almost the same. These were actually confirmed. It was also confirmed that the communication area expanded in proportion to the area of the closed loop circuit 5.

In this embodiment, the closed loop circuit 5
Is a resonance circuit, but need not be a resonance circuit.
Although the number of magnetic fluxes generated in the closed loop circuit 5 is reduced, it may be formed only by the coil 5a.

The shape of the loop antenna 3 or 4 to be electromagnetically coupled to the closed loop circuit 5 is quadrangular, but may be other than that. Specifically, the shape may be a circle or a triangle. This is the same for the shape of the coil 5a. The closed loop circuit 5 may be electromagnetically coupled to an antenna of a type different from the loop antenna (such as a bar antenna in which a wire is wound around a rod-shaped ferrite core).

In the present embodiment, the two antennas 3 and 4 are electromagnetically coupled to the closed loop circuit 5, but the number is not limited to two. It may be larger or smaller. For example, at least one of the antennas 3 and 4 may be further provided with one or more closed loop circuits that are electromagnetically coupled to only one of them. As is apparent from this, the present invention can expand the communication area while avoiding the occurrence of an area with low reception sensitivity regardless of the number of antennas.

The closed loop circuit may be manufactured separately from the antenna and arranged at a place where the magnetic flux density is relatively small (a position corresponding to an area where the magnetic flux density is desired to be larger in the communication area). . In such a case, the communication area of the already installed antenna can be expanded. As is clear from this,
The present invention can be applied to existing antennas. <Second Embodiment> FIG. 3 is a diagram illustrating the configuration of an antenna unit according to a second embodiment. FIG. 2A is a perspective view when viewed from the front direction side, and FIG.
Is a side view. In FIG. 3, the same or basically the same components as those in the first embodiment are denoted by the same reference numerals.

As shown in FIG. 3 (a), the antenna unit 1 has a loop antenna 11 on which a wire is printed several turns on an antenna substrate 2, and an electromagnetic antenna that sandwiches the antenna 11 therebetween. And two closed loop circuits 12 arranged at positions coupled to the circuit. The closed loop circuit 12 is not particularly shown,
As in the first embodiment, a parallel resonance circuit is formed by connecting a coil (for example, an external capacitor) and a coil printed on the antenna substrate 2 with several turns of a wire.

The loop antenna 11 has a driver 7
Amplifies and feeds the signal from the oscillator 8. As a result, a magnetic flux is generated in the loop antenna 11, and a part of the magnetic flux links with the closed loop circuit 12. Due to the linkage of the magnetic flux, a current flows through each of the two closed loop circuits 12 so as to cancel the magnetic flux. When a magnetic flux 13 is generated in the loop antenna 11 by the power supply from the driver 7 as shown in FIG. 3A, a part of the magnetic flux 13 is linked to each of the closed loop circuits 12 in a direction indicated by an arrow. Electric current flows. As a result, each closed loop circuit 12 behaves as an antenna that generates a magnetic flux so as to supplement the magnetic flux 13 generated by the antenna 11 while being disposed at a position that is electromagnetically coupled to the loop antenna 11.

As shown in FIG. 3B, the surface of each closed loop circuit 12 is made flush with the surface of the loop antenna 11. Thereby, the magnetic flux generated in each closed loop circuit 12 mainly compensates for the outside of the magnetic flux 13 generated in the loop antenna 11, and acts to expand the communication area while avoiding the generation of the low sensitivity area. Will do.

In the present embodiment, the closed loop circuit 12 is arranged so as to sandwich one loop antenna 11 from above and below, but, for example, as shown in FIG. A closed loop circuit 21 may be provided. In such a case, the communication area can be made wider while avoiding the occurrence of the low-sensitivity area. Otherwise, two closed loop circuits 21 may be arranged instead of the two closed loop circuits 12, and one closed loop circuit 12 and one closed loop circuit 21 may be arranged.
May be arranged. As is clear from these things,
The arrangement of the closed loop circuit can be variously modified.
As a matter of course, the shape of the closed loop circuit needs to be determined according to each shape of the loop antenna 11 and other closed loop circuits, and how to arrange them. <Third Embodiment> In the first and second embodiments, the closed loop circuit is arranged so that its surface is flush with the surface of the loop antenna. On the other hand, in the third embodiment, the arrangement is made such that the surfaces are not on the same plane.

FIG. 5 is a diagram for explaining the configuration of the antenna unit according to the third embodiment. FIG. 1A is a perspective view when viewed from the front side, and FIG. 1B is a side view. In FIG. 5, the same as the second embodiment,
Alternatively, basically the same components are denoted by the same reference numerals. The antenna substrate 2, the driver 7, and the oscillator 8 are omitted.

As shown in FIG. 5A, the antenna unit 1 is provided with two closed loop circuits 31 electromagnetically coupled to the loop antenna 11 so as to sandwich the loop antenna 11 from above and below. However, each closed loop circuit 31
5B, for example, by providing a step on the antenna substrate 2 so as to be parallel to the surface of the loop antenna 11 and forward of the surface of the antenna 11 by a distance a in the front direction as shown in FIG. Is located. Although not shown, each closed loop circuit 31 has a coil and a capacitor (for example, an external capacitor) formed by printing a few turns of a wire on the antenna substrate 2 as in the first and second embodiments. ) Is connected to the parallel resonance circuit.

As described above, even if a step is provided between the surface of the loop antenna 11 and the surface of the closed loop circuit 31, a part of the magnetic flux generated in the antenna 11 is linked to the closed loop circuit 31. For this reason, as in the first and second embodiments, the closed loop circuit 31 functions as an antenna. By providing the step, the distance between the antenna 11 and the closed loop circuit 31 on a plane including the surface of the loop antenna 11 can be further reduced. Therefore, there is also an effect that the closed loop circuit 31 can be more strongly electromagnetically coupled to the loop antenna 11.

In this embodiment, the closed loop circuit 31 having a step is provided so as to sandwich one loop antenna 11 from above and below. However, as shown in FIG. 6, for example, as shown in FIG. In this way, the closed loop circuit 41 having two steps may be arranged. In such a case, the communication area can be made wider while avoiding the occurrence of the low-sensitivity area. Otherwise, two closed loop circuits 41 may be arranged instead of the two closed loop circuits 31, or one closed loop circuit 31 and one closed loop circuit 41 may be arranged. Regarding the step, for example, there may be some of the closed loop circuits 31 and 41 that are not provided. As is apparent from the above, even if a step is provided, the arrangement of the closed loop circuit can be variously modified. <Fourth Embodiment> In the first to third embodiments, the surface of the closed loop circuit is parallel to the surface of the loop antenna. On the other hand, in the fourth embodiment, the arrangement is made such that the surfaces are not parallel.

FIG. 7 is a diagram for explaining the configuration of the antenna unit according to the fourth embodiment. FIG. 1A is a perspective view when viewed from the front side, and FIG. 1B is a side view. In FIG. 7, the same as the second embodiment,
Alternatively, basically the same components are denoted by the same reference numerals. The antenna substrate 2, the driver 7, and the oscillator 8 are omitted.

As shown in FIG. 7A, the antenna unit 1 is provided with two closed loop circuits 51 electromagnetically coupled to the loop antenna 11 so as to sandwich the loop antenna 11 from above and below. However, each closed loop circuit 51
The surface of the closed loop circuit 51 is inclined with respect to the surface of the loop antenna 11 as shown in FIG. Although not shown, each closed-loop circuit 31 has a first and a second circuit.
As in the embodiment of FIG.
This is a parallel resonance circuit in which a coil printed above and a capacitor (for example, an external capacitor) are connected.

In FIG. 7B, α is the loop antenna 11
Is perpendicular to the surface of the closed loop circuit 51, and these perpendiculars intersect on the front side of the antenna unit 1. The angle α is determined, for example, based on a distance (maximum distance) at which communication can be performed by the antenna unit 1 and a communication area. Since the angle α is provided, more magnetic flux generated in the closed loop circuit 51 gathers in the communication area as compared with the first to third embodiments, and the magnetic flux density of the communication area can be increased. it can.

In the fourth embodiment, the closed loop circuit 51 having a tilt is provided so as to sandwich one loop antenna 11 from above and below, but for example, as shown in FIG. A closed loop circuit 61 having two inclinations so as to be sandwiched from the direction may be arranged. In such a case, the communication area can be made wider while avoiding the occurrence of the low-sensitivity area. In addition, two closed loop circuits 61 may be arranged instead of the two closed loop circuits 51, and one closed loop circuit 51 and one closed loop circuit 61 may be arranged. Regarding the inclination, for example, some of the closed-loop circuits 51 and 61 may not have the inclination. As is clear from these, even if the inclination is provided, the arrangement of the closed loop circuit can be variously modified.

This embodiment (first to fourth embodiments)
It is assumed that the antenna unit according to the present invention is mounted on a device that communicates with an IC card constituting various gate systems, electronic commerce systems, or transportation access systems. It is not limited to such a device. Any device that needs to maintain reception sensitivity uniformly in a communication area can be widely applied.

[0045]

As described above, according to the present invention, a closed loop circuit is arranged at a position where it is electromagnetically coupled to an antenna,
A magnetic field is generated in the closed loop circuit according to the magnetic field generated in the antenna. This allows the closed loop circuit to behave like an antenna, thereby expanding the communication area while avoiding the generation of a low-sensitivity area (an area in which the magnetic flux density is significantly lower than others). It has been confirmed that the communication area can be expanded according to the area of the closed loop circuit.

For example, when the antenna is arranged between two antennas, the closed loop circuit works to supplement the magnetic flux to be generated between them. For this reason, when arranging a plurality of antennas, by arranging a closed loop circuit between each antenna, it is possible to expand a communication area while avoiding the generation of a low-sensitivity area.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an antenna unit according to a first embodiment.

FIG. 2 is a diagram illustrating a magnetic field generated in the antenna unit according to the first embodiment.

FIG. 3 is a diagram illustrating a configuration of an antenna unit according to a second embodiment.

FIG. 4 is a diagram illustrating a modified example of the second embodiment.

FIG. 5 is a diagram illustrating a configuration of an antenna unit according to a third embodiment.

FIG. 6 is a diagram illustrating a modification of the third embodiment.

FIG. 7 is a diagram illustrating a configuration of an antenna unit according to a fourth embodiment.

FIG. 8 is a diagram illustrating a modification of the fourth embodiment.

FIG. 9 is a diagram showing an example of a layout of a conventional loop antenna.

FIG. 10 is a diagram illustrating a magnetic field generated when the distance between loop antennas is increased.

[Explanation of symbols]

Reference Signs List 1 antenna unit 2 antenna board 3, 4, 11 loop antenna 5, 12, 21, 31, 41, 51, 61 closed loop circuit 5a coil 5b capacitor 7 driver 8 oscillator 8 oscillator 10 antenna (IC card)

Claims (6)

[Claims] 1. An antenna unit comprising: at least one antenna that is supplied with power to generate a magnetic flux; and at least one closed loop circuit that is electromagnetically coupled to the antenna. 2. The antenna unit according to claim 1, wherein the closed loop circuit is a resonance circuit configured by connecting a coil and a capacitor. 3. The antenna unit according to claim 1, wherein the closed loop circuit is arranged such that a surface formed by a line of the circuit is parallel to a surface of the antenna. . 4. The antenna unit according to claim 3, wherein the surface of the closed loop circuit is arranged at a position other than a plane including the surface of the antenna. 5. The closed loop circuit according to claim 1, wherein a perpendicular of a surface formed by a line of the circuit intersects with a perpendicular of a surface of the antenna. Antenna unit. 6. A method for expanding an area in which communication is possible with an antenna, comprising: arranging at least one closed loop circuit at a position electromagnetically coupled to the antenna, and operating the closed loop circuit as an antenna. A method for expanding a communication area, comprising expanding an area.