Magnetic field signal generation system

Abstract

The present invention provides a magnetic field signal generation system that can form a communication area conforming to the shape of any target space without requiring an excessive number of antennas or causing communication delays. [Solution] The magnetic field signal generation system comprises a plurality of coil antennas 1-1 to 1-4, each having a winding wound around an axis, and a drive device 2 that drives each of the plurality of coil antennas to generate a magnetic field signal. The plurality of coil antennas are arranged in predetermined positions such that the same magnetic poles of a pair of coil antennas face each other, and are driven simultaneously by the drive device.

Description

Technical Field

[0001] The present disclosure relates to a magnetic field signal generation system.

Background Art

[0002] Conventionally, short-range wireless communication systems having a communication range of several meters are used, for example, to remotely unlock and lock keys.

[0003] For example, Patent Document 1 discloses a wireless door lock control device for a vehicle that is configured to control locking / unlocking of the vehicle door according to the presence or absence of radio waves transmitted from a transmitter carried by a driver.

[0004] Such a short-range wireless communication system may be configured as a magnetic field signal generation system that includes a coil antenna and generates magnetic field signals in the VLF band or LF band.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Conventional magnetic field signal generation systems provided with coil antennas have the following problems.

[0007] First, a single antenna is generally used to form the communicable area of a magnetic field signal generation system, but since a single antenna has a spherical radiation pattern, sufficient design flexibility may not be ensured.

[0008] Secondly, when using a single antenna, expanding the communication area requires increasing the size of the antenna and / or the drive current. This can lead to increased costs and potentially structural or electrical constraints.

[0009] Thirdly, it is difficult to form a communication area that conforms to the shape of an arbitrary target space (e.g., a rectangular prism). To form a communication area with a desired shape, one might consider sequentially driving multiple antennas placed in the target space. In this case, due to the spherical radiation pattern of the antennas as described above, there is a possibility that areas where the magnetic field signal is difficult to reach may occur. In order to make the magnetic field signal reach each point in the target space, it is necessary to place many antennas at short intervals. Also, in this case, since multiple antennas are driven sequentially, communication delays may occur.

[0010] Therefore, it is necessary to form a communication area that conforms to the shape of any target space without requiring an excessive number of antennas or causing communication delays.

[0011] The purpose of this disclosure is to provide a magnetic field signal generation system that can form a communication area that conforms to the shape of any target space without requiring an excessive number of antennas and without causing communication delays. [Means for solving the problem]

[0012] A magnetic field signal generation system according to the first aspect of this disclosure is: Multiple coil antennas, each having a winding wound around an axis, The system includes a drive device that drives each of the plurality of coil antennas to generate a magnetic field signal using the plurality of coil antennas, The plurality of coil antennas are arranged in predetermined positions such that the same magnetic poles of a pair of coil antennas face each other, and are driven simultaneously by the drive device.

[0013] According to the magnetic field signal generation system of the second aspect of this disclosure, in the magnetic field signal generation system of the first aspect, The plurality of coil antennas are each arranged on a reference plane including the reference point such that the axis of each coil antenna passes through a predetermined vicinity of the reference point.

[0014] According to the magnetic field signal generation system of the third aspect of this disclosure, in the magnetic field signal generation system of the second aspect, The plurality of coil antennas are arranged such that the axis of each coil antenna is parallel to the reference plane.

[0015] According to the magnetic field signal generation system of the fourth aspect of this disclosure, in the magnetic field signal generation system of the second aspect, The plurality of coil antennas are arranged such that the axis of each coil antenna has a predetermined angle less than 45 degrees with respect to the reference plane.

[0016] According to the magnetic field signal generation system of the fifth aspect of this disclosure, in the magnetic field signal generation system of the first aspect, The plurality of coil antennas are arranged such that the axes of each coil antenna are aligned on the same straight line. The plurality of coil antennas are driven simultaneously by the drive device such that the same magnetic poles of each adjacent pair of coil antennas face each other.

[0017] According to the magnetic field signal generation system of the sixth aspect of this disclosure, in the magnetic field signal generation system of one of the first to fifth aspects, The drive device drives the plurality of coil antennas with AC signals having the same frequency and the same phase.

[0018] A magnetic field signal generation system according to the seventh aspect of this disclosure is: Multiple coil antennas, each having a winding wound around an axis, and a drive device that respectively drives the plurality of coil antennas so as to generate magnetic field signals by the plurality of coil antennas, the plurality of coil antennas are respectively arranged on a reference plane including a reference point such that the axis of each of the coil antennas passes through a predetermined vicinity of the reference point, the plurality of coil antennas are connected in parallel to the drive device.

[0019] According to the magnetic field signal generation system according to the eighth aspect of the present disclosure, the magnetic field signal generation system according to any one of the first to seventh aspects, a mobile device that receives the magnetic field signals generated by the plurality of coil antennas, and further comprising a processing device that determines, based on the magnetic field signals received by the mobile device, whether or not the mobile device has entered a communicable area including the plurality of coil antennas.

[0020] According to the magnetic field signal generation system according to the ninth aspect of the present disclosure, the magnetic field signal generation system according to any one of the second to fourth aspects, a mobile device that receives the magnetic field signals generated by the plurality of coil antennas, and further comprising a processing device that calculates the distance of the mobile device relative to the reference plane based on the magnetic field signals received by the mobile device. [Advantageous Effects of the Invention]

[0021] According to the magnetic field signal generation system according to one aspect of the present disclosure, it is possible to form a communicable area in conformity with the shape of any target space without requiring an excessively large number of antennas and without causing communication delay. [Brief Description of the Drawings]

[0022] [Figure 1] It is a diagram showing the configuration of the magnetic field signal generation system according to the first embodiment. [Figure 2] It is a diagram showing the configuration of the coil antenna 1 of Fig. 1. [Figure 3]This diagram shows the configuration of a magnetic field signal generation system related to a comparative example. [Figure 4] This figure shows the magnetic flux generated by coil antennas 1-11 and 1-13 in Figure 3. [Figure 5] This figure shows the equimagnetic field strength lines generated by coil antennas 1-11 and 1-13 in Figure 3. [Figure 6] This figure shows the magnetic field strength in the vertical plane generated by the coil antenna 1-11 in Figure 3. [Figure 7] This figure shows the magnetic field strength in the horizontal plane generated by coil antennas 1-11 to 1-14 in Figure 3. [Figure 8] This diagram shows the magnetic flux generated by coil antennas 1-1 and 1-3 in Figure 1. [Figure 9] This figure shows the equimagnetic field strength lines generated by coil antennas 1-1 and 1-3 in Figure 1. [Figure 10] This figure shows the magnetic field strength in the vertical plane generated by coil antennas 1-1 to 1-4 in Figure 1. [Figure 11] This figure shows the magnetic field strength in the horizontal plane generated by coil antennas 1-1 to 1-4 in Figure 1. [Figure 12] This diagram shows the configuration of a magnetic field signal generation system according to a first modification of the first embodiment. [Figure 13] This diagram shows the configuration of a magnetic field signal generation system according to a second modified example of the first embodiment. [Figure 14] This figure shows the magnetic field strength in the vertical plane generated by coil antennas 1-31 to 1-34 in Figure 13. [Figure 15] This figure shows the magnetic field strength in the horizontal plane generated by coil antennas 1-31 to 1-34 in Figure 13. [Figure 16] This figure shows the configuration of the magnetic field signal generation system according to the second embodiment. [Figure 17] This figure shows the magnetic field strength in the vertical plane generated by coil antennas 1-41 to 1-43 in Figure 16. [Figure 18]This figure shows the configuration of a magnetic field signal generation system according to the third embodiment. [Figure 19] This is a block diagram showing the configuration of the mobile device 3 in Figure 18. [Figure 20] This figure shows the communicationable areas 41-46 of the magnetic field signal generation system according to the first modification of the third embodiment. [Figure 21] This figure shows points P1 to P6 on the reference plane of a magnetic field signal generation system according to a second modified example of the third embodiment. [Figure 22] This graph shows the magnetic flux density at points P1 to P6 in Figure 21, with respect to the height of the mobile device 3. [Figure 23] This graph shows the relationship between the actual height and the calculated height of the mobile device 3 at each point P1 to P6 in Figure 21. [Modes for carrying out the invention]

[0023] The embodiments of this disclosure will be described below with reference to the attached drawings.

[0024] [First Embodiment] Figure 1 shows the configuration of a magnetic field signal generation system according to the first embodiment. The magnetic field signal generation system in Figure 1 includes coil antennas 1-1 to 1-4 and a drive device 2.

[0025] In this specification, coil antennas 1-1 to 1-4 (and coil antennas 1-11 to 1-43 described later) are collectively referred to as "coil antenna 1," and each coil antenna 1 is configured similarly.

[0026] Figure 2 shows the configuration of the coil antenna 1 shown in Figure 1. The coil antenna 1 comprises a magnetic core 11, a winding 12, and a capacitor C0. The magnetic core 11 has a longitudinal axis A0. The winding 12 is wound around the magnetic core 11, i.e., around axis A0. The winding 12 and the capacitor C0 together constitute a resonant circuit.

[0027] The coil antennas 1-1 to 1-4 are each positioned on a plane parallel to the XY plane (hereinafter referred to as the "reference plane"). The coil antennas 1-1 to 1-4 are each positioned such that the axis A0 of each coil antenna 1 passes through a predetermined vicinity of the reference point O on the reference plane. Here, the vicinity of the reference point O refers to the region within a predetermined radius from the reference point O within the area surrounded by the coil antennas 1-1 to 1-4. In the example in Figure 1, the coil antennas 1-1 to 1-4 are each positioned such that the axis A0 of each coil antenna 1 is parallel to the reference plane, that is, the axis A0 of each coil antenna 1 is included in the reference plane. The coil antennas 1-1 to 1-4 may also be positioned around the reference point O at equal angles to each other, for example, at intervals of 90 degrees.

[0028] The drive unit 2 drives the coil antennas 1-1 to 1-4 to generate magnetic field signals. The magnetic field signals may have frequencies in the very low frequency (VLF) band of 3 to 30 kHz, the long frequency (LF) band of 30 to 300 kHz, or other frequency bands. The drive unit 2 drives the coil antennas 1-1 to 1-4 with AC signals having the same frequency and substantially the same phase. The AC signals supplied by the drive unit 2 may have a predetermined phase difference, provided they are substantially in phase. To drive the coil antennas 1-1 to 1-4 with the same frequency and phase, the coil antennas 1-1 to 1-4 may be connected in parallel to one output terminal of the drive unit 2, or they may be connected to multiple synchronized drive units.

[0029] Coil antennas 1-1 to 1-4 are positioned in predetermined locations such that the same magnetic poles of a pair of coil antennas 1 face each other, and are driven simultaneously by the drive unit 2. More specifically, at a certain moment in each cycle of the AC signal supplied by the drive unit 2, the same magnetic poles N of coil antennas 1-1 and 1-3 face each other, and the same magnetic poles N of coil antennas 1-2 and 1-4 face each other. Also, at another moment in each cycle of the AC signal, the same magnetic poles S of coil antennas 1-1 and 1-3 face each other, and the same magnetic poles S of coil antennas 1-2 and 1-4 face each other. In other words, at a certain moment, a magnetic pole N is generated at the end of each coil antenna 1-1 to 1-4 that is closer to the reference point O, and at another moment, a magnetic pole S is generated at the same end.

[0030] Here, with reference to Figures 3 to 7, a magnetic field signal generation system related to a comparative example will be described.

[0031] Figure 3 shows the configuration of a magnetic field signal generation system according to a comparative example. The magnetic field signal generation system in Figure 3 comprises coil antennas 1-11 to 1-14 and a drive device 2. In the example in Figure 3, the coil antennas 1-11 to 1-14 are arranged such that the axis A0 of each coil antenna 1 is perpendicular to the reference plane. The coil antennas 1-11 to 1-14 are simultaneously driven by the drive device 2 such that, at a certain moment in each cycle of the AC signal supplied by the drive device 2, a magnetic pole N is generated at the +Z end of each coil antenna 1, and at another moment, a magnetic pole S is generated at the same end.

[0032] Figure 4 shows the magnetic flux generated by coil antennas 1-11 and 1-13 in Figure 3. The magnetic flux generated in the upper left of coil antenna 1-11 has the opposite direction to the magnetic flux generated in the upper right of coil antenna 1-13, and the magnetic fields weaken each other. Similarly, the magnetic flux generated in the lower left of coil antenna 1-11 has the opposite direction to the magnetic flux generated in the lower right of coil antenna 1-13, and the magnetic fields weaken each other.

[0033] Figure 5 shows the equimagnetic field strength lines generated by coil antennas 1-11 and 1-13 in Figure 3. As explained with reference to Figure 4, the magnetic fields generated by coil antennas 1-11 and 1-13 weaken each other, causing the magnetic field strength to decrease at intermediate positions between coil antennas 1-11 and 1-13, i.e., above and below reference point O.

[0034] The magnetic fields generated by coil antennas 1-12 and 1-14 in Figure 3 also weaken each other, causing the magnetic field strength to decrease above and below reference point O.

[0035] Figure 6 shows the magnetic field strength in the vertical plane generated by coil antennas 1-11 in Figure 3. Figure 7 shows the magnetic field strength in the horizontal plane generated by coil antennas 1-11 to 1-14 in Figure 3. According to Figure 7, even though the four coil antennas 1-11 to 1-14 are driven simultaneously, the magnetic field strength decreases at intermediate positions between coil antennas 1-11 to 1-14, i.e., above and below reference point O.

[0036] As shown in Figure 5, the magnetic field strength decreases above and below the reference point O, making it difficult for the magnetic field signal to reach the target area. Conventionally, to overcome this decrease in magnetic field strength, it was necessary to place a larger number of antennas at shorter intervals. In contrast, with reference to Figures 8 to 11, a magnetic field signal generation system according to an embodiment that can form a communicationable area according to the shape of any target space without requiring an excessive number of antennas or causing communication delays will be described below.

[0037] Figure 8 shows the magnetic flux generated by coil antennas 1-1 and 1-3 in Figure 1. The magnetic flux generated to the left of coil antenna 1-1 has the opposite direction to the magnetic flux generated to the right of coil antenna 1-3, and the magnetic fields weaken each other. However, the magnetic flux generated to the upper left of coil antenna 1-1 has the same direction as the magnetic flux generated to the upper right of coil antenna 1-3, and the magnetic fields strengthen each other. Similarly, the magnetic flux generated to the lower left of coil antenna 1-1 has the same direction as the magnetic flux generated to the lower right of coil antenna 1-3, and the magnetic fields strengthen each other.

[0038] Figure 9 shows the equimagnetic field strength lines generated by coil antennas 1-1 and 1-3 in Figure 1. As explained with reference to Figure 8, the magnetic fields generated by coil antennas 1-1 and 1-3 reinforce each other, resulting in magnetic fields equal to or greater than those above and below coil antennas 1-1 and 1-3 being generated at intermediate positions between coil antennas 1-1 and 1-3, i.e., above and below reference point O.

[0039] The magnetic fields generated by coil antennas 1-2 and 1-4 in Figure 1 also reinforce each other, resulting in magnetic fields above and below reference point O that are equal to or greater than those above and below coil antennas 1-1 and 1-3.

[0040] Figure 10 shows the magnetic field strength in the vertical plane generated by the coil antennas 1-1 to 1-4 in Figure 1. Figure 11 shows the magnetic field strength in the horizontal plane generated by the coil antennas 1-1 to 1-4 in Figure 1. Figure 11 shows the magnetic field strength 1 m above the reference plane. Figures 10 and 11 show that by superimposing the magnetic fields generated by the coil antennas 1-1 to 1-4, a larger communication area can be constructed than when using a single coil antenna. Comparing Figures 7 and 10, it can be seen that the magnetic field signal generation system in Figure 1 can mitigate the decrease in magnetic field strength above and below the reference point O. Referring to Figure 11, it can be seen that the magnetic field signal generation system in Figure 1 can form a substantially square communication area by arranging the four coil antennas 1-1 to 1-4.

[0041] According to the magnetic field signal generation system in Figure 1, a communication area with a flat magnetic field strength distribution when viewed from the side can be formed, as shown in Figure 9. In particular, a sufficiently strong magnetic field strength can be achieved above and below the reference point O, even though it is far from each coil antenna 1-1 to 1-4, so as a result, the number of coil antennas required can be reduced.

[0042] Furthermore, the magnetic field signal generation system shown in Figure 1 can form a square (or rectangular) communication area when viewed from above, as shown in Figure 11. This allows for the efficient formation of a communication area to match, for example, a rectangular target space (such as a room). Also, as will be described later with reference to Figure 20, a wide-area communication area can be formed by arranging multiple communication areas regularly and efficiently.

[0043] According to the magnetic field signal generation system in Figure 1, by combining multiple coil antennas 1-1 to 1-4, design flexibility can be improved compared to using a single antenna with a spherical radiation pattern. Furthermore, since the magnetic field signal generation system in Figure 1 does not require larger antennas and / or increased drive current, it can be implemented at a relatively low cost without being subject to structural or electrical constraints. In addition, since the magnetic field signal generation system in Figure 1 drives multiple coil antennas 1-1 to 1-4 simultaneously, a system with high responsiveness can be realized without causing communication delays.

[0044] Thus, the magnetic field signal generation system shown in Figure 1 can create a communication area that conforms to the shape of any target space without requiring an excessive number of antennas or causing communication delays.

[0045] Figure 12 shows the configuration of a magnetic field signal generation system according to a first modification of the first embodiment. The magnetic field signal generation system in Figure 12 comprises three coil antennas 1-21 to 1-23 and a drive device 2 (not shown). The coil antennas 1-21 to 1-23 may be arranged around a reference point O at equal angles to each other, for example, at intervals of 120 degrees. The coil antennas 1-21 to 1-23 are simultaneously driven by the drive device 2 such that, at a given moment in each cycle of the AC signal supplied by the drive device 2, a magnetic pole N is generated at the end of each coil antenna 1 closer to the reference point O, and at another moment, a magnetic pole S is generated at the same end. According to the magnetic field signal generation system in Figure 12, a communication area can be formed to match the shape of any target space (e.g., a triangle) without requiring an excessive number of antennas and without causing communication delays.

[0046] The magnetic field signal generation system may have two coil antennas, or it may have five or more coil antennas.

[0047] Figure 13 shows the configuration of a magnetic field signal generation system according to a second modification of the first embodiment. The magnetic field signal generation system in Figure 13 comprises coil antennas 1-31 to 1-34 and a drive device 2. The coil antennas 1-31 to 1-34 are arranged such that the axis A0 of each coil antenna 1 has a predetermined angle θ less than 45 degrees with respect to the reference plane. By adjusting the angle θ, the magnetic field strength above (or below) the reference point O can be increased.

[0048] Figure 14 shows the magnetic field strength in the vertical plane generated by coil antennas 1-31 to 1-34 in Figure 13. Figure 15 shows the magnetic field strength in the horizontal plane generated by coil antennas 1-31 to 1-34 in Figure 13. Figure 15 also shows the magnetic field strength 1 m above the reference plane. Figures 14 and 15 show the magnetic field strength when the axis A0 of each coil antenna 1 is positioned such that it has an angle θ = 20 degrees with respect to the reference plane. Comparing Figures 10 and 14, it can be seen that the magnetic field signal generation system in Figure 13 has a distribution of strengthened magnetic field strength above the reference point O. As a result, the magnetic field signal generation system in Figure 13 forms a communication area that is wider above the reference point O. Furthermore, comparing Figures 11 and 15, it can be seen that the magnetic field signal generation system in Figure 13 forms a substantially square communication area without any dips. The inventors confirmed the increase in magnetic field strength through simulation and actual measurement.

[0049] The magnetic field strength is proportional to the square of the input power. The magnetic field signal generation system in Figure 13 has a communication area equivalent to that of the magnetic field signal generation system in Figure 1, but with a range of 0.8 2 It can be produced with 64% less energy, significantly reducing energy consumption.

[0050] [Second Embodiment] Figure 16 shows the configuration of a magnetic field signal generation system according to the second embodiment. The magnetic field signal generation system in Figure 16 comprises three coil antennas 1-41 to 1-43 and a drive device 2 (not shown). The coil antennas 1-41 to 1-43 are arranged so that the axes of each coil antenna 1 are aligned on the same straight line. The coil antennas 1-41 to 1-43 are simultaneously driven by the drive device 2 so that the same magnetic poles of each adjacent pair of coil antennas 1 face each other. Specifically, at a certain moment in each cycle of the AC signal supplied by the drive device 2, the same magnetic poles S of coil antennas 1-41 and 1-42 face each other, and the same magnetic poles N of coil antennas 1-42 and 1-43 face each other. Also, at another moment in each cycle of the AC signal, the same magnetic poles N of coil antennas 1-41 and 1-42 face each other, and the same magnetic poles S of coil antennas 1-42 and 1-43 face each other.

[0051] Figure 17 shows the magnetic field strength in the vertical plane generated by coil antennas 1-41 to 1-43 in Figure 16. According to Figure 17, it can be seen that the magnetic field signal generation system in Figure 16 can generate a flat distribution of magnetic field strength over a wide range.

[0052] The magnetic field signal generation system according to this embodiment may include four or more coil antennas arranged to be aligned on the same straight line.

[0053] [Third Embodiment] Figure 18 shows the configuration of a magnetic field signal generation system according to a third embodiment. The magnetic field signal generation system in Figure 19 includes, in addition to the components of the magnetic field signal generation system in Figure 1, a mobile device 3, an access point device (AP) 4, and a processing device 5.

[0054] Coil antennas 1-1 to 1-4 form a communication area 40, which is the range over which magnetic field signals can be transmitted.

[0055] Figure 19 is a block diagram showing the configuration of the mobile device 3 in Figure 18. The mobile device 3 comprises a receiving circuit 31, a signal processing circuit 32, and a transmitting circuit 33. The receiving circuit 31 receives magnetic field signals generated by coil antennas 1-1 to 1-4. The signal processing circuit 32 measures the signal level of the received magnetic field signals. The transmitting circuit 33 transmits the signal level of the magnetic field signals to the access point device 4.

[0056] The access point device 4 receives the signal level of the magnetic field signal received by the mobile device 3 from the mobile device 3 and sends it to the processing device 5.

[0057] The processing unit 5 determines whether the mobile device 3 has entered the communication area 40 based on the signal level of the magnetic field signal received by the mobile device 3. The processing unit 5 may also determine that the mobile device 3 has entered the communication area 40 if the signal level of the magnetic field signal exceeds a predetermined threshold. Furthermore, the processing unit 5 may determine that the mobile device 3 has entered the communication area 40 if it receives a signal level of the magnetic field signal from the mobile device 3 (i.e., the mobile device 3 has received the magnetic field signal).

[0058] Each of the coil antennas 1-1 to 1-4 has a communication range, for example, a radius of 1 to 2 m. In this case, the magnetic field signal generation system combines the four coil antennas 1-1 to 1-4 to form a communication range, or communication area, with a radius of 3 to 10 m.

[0059] Figure 20 shows the communicationable areas 41-46 of a magnetic field signal generation system according to a first modification of the third embodiment. The magnetic field signal generation system may include a plurality of communicationable areas 41-46 arranged adjacent to each other. The magnetic field signal generation system of Figure 20 comprises a plurality of coil antennas 1 and drive devices 2 (not shown) associated with each of the communicationable areas 41-46 and configured similarly to the magnetic field signal generation system of Figure 1 or Figure 13. Since the magnetic field signal generation systems of Figures 1 and 13 generate substantially square (or rectangular) communicationable areas (see Figures 11 and 15), the communicationable areas 41-46 can be arranged regularly and efficiently with minimal overlap. Each drive device 2 of each communicationable area 41-46 generates a mutually identifiable magnetic field signal, for example, a magnetic field signal having different frequencies. This makes it possible to determine which of the communicationable areas 41-46 the mobile device 3 has entered.

[0060] Figure 21 shows points P1 to P6 on a reference plane of a magnetic field signal generation system according to a second modified example of the third embodiment. The processing device 5 in Figure 18 may be configured to calculate the distance (i.e., height) of the mobile device 3 to the reference plane based on the magnetic field signal received by the mobile device 3.

[0061] Theoretically, magnetic flux density decreases in proportion to the 1 / 3 power of the distance, but in the configuration of the magnetic field signal generation system according to this embodiment, it decreases exponentially. Therefore, the height h (in m) of the moving device 3 with respect to the reference plane can be calculated by the following formula.

[0062] h = -A1·log(B)-A2

[0063] Here, B represents the magnetic flux density (in units of T), and A1 and A2 are constants derived empirically from measurements. For example, A1 = 1.04 and A2 = 17.7.

[0064] When the mobile device 3 is located at a predetermined height h on points P1 to P6, the height h was calculated based on the magnetic flux density B. Points P1 to P6 have the following coordinates (in mm).

[0065] P1 (0,0) P2 (350,350) P3 (700,0) P4 (700,700) P5 (1050,350) P6 (1300,0)

[0066] Figure 22 is a graph showing the magnetic flux density with respect to the height of the mobile device 3 at each point P1 to P6 in Figure 21. Figure 23 is a graph showing the relationship between the actual height and the calculated height of the mobile device 3 at each point P1 to P6 in Figure 21. Figures 22 and 23 show that the height h can be calculated with high accuracy regardless of whether the mobile device 3 is above any of the points P1 to P6.

[0067] The magnetic field signal generation systems shown in Figures 1 and 13 form a communication area with a flat magnetic field strength distribution when viewed from the side (see Figures 10 and 14), so the height h of the mobile device 3 relative to the reference plane can be easily and accurately calculated above the reference point O.

[0068] The mobile device 3 is equipped with a processing unit 5, which may determine whether the mobile device 3 has entered the communication area 40, and / or calculate the height h of the mobile device 3 with respect to a reference plane.

[0069] The magnetic field signal generation system may be configured to transmit a magnetic field signal from the mobile device and receive the magnetic field signal with a plurality of coil antennas 1. In this case as well, it is possible to determine whether the mobile device has entered the communication area 40 and / or calculate the height h of the mobile device 3 relative to the reference plane based on the signal level of the magnetic field signal. [Industrial applicability]

[0070] This disclosure is applicable, for example, to passive entry systems or smart entry systems that remotely unlock and lock a vehicle. [Explanation of Symbols]

[0071] 1. Coil antenna 2. Drive unit 3 Mobile device 4. Access Point Device (AP) 5 Processing Unit 11 Magnetic core 12 windings C0 Capacitor 31 Receiving circuit 32 Signal Processing Circuits 33 Transmitter Circuit 40-46 Communication coverage area

Claims

1. Multiple coil antennas, each having a winding wound around an axis, The system includes a drive device that drives each of the plurality of coil antennas to generate a magnetic field signal using the plurality of coil antennas, The plurality of coil antennas are arranged in predetermined positions such that the same magnetic poles of a pair of coil antennas face each other, and are driven simultaneously by the drive device. Magnetic field signal generation system.

2. The plurality of coil antennas are each arranged on a reference plane including the reference point such that the axis of each coil antenna passes through a predetermined vicinity of the reference point. A magnetic field signal generation system according to claim 1.

3. The plurality of coil antennas are arranged such that the axis of each coil antenna is parallel to the reference plane. The magnetic field signal generation system according to claim 2.

4. The plurality of coil antennas are arranged such that the axis of each coil antenna is at a predetermined angle less than 45 degrees with respect to the reference plane. The magnetic field signal generation system according to claim 2.

5. The plurality of coil antennas are arranged such that the axes of each coil antenna are aligned on the same straight line. The plurality of coil antennas are driven simultaneously by the drive device such that the same magnetic poles of each adjacent pair of coil antennas among the plurality of coil antennas face each other. A magnetic field signal generation system according to claim 1.

6. The drive device drives the plurality of coil antennas with AC signals having the same frequency and the same phase. A magnetic field signal generation system according to one of claims 1 to 5.

7. Multiple coil antennas, each having a winding wound around an axis, The system includes a drive device that drives each of the plurality of coil antennas to generate a magnetic field signal using the plurality of coil antennas, The plurality of coil antennas are each arranged on a reference plane including the reference point such that the axis of each coil antenna passes through a predetermined vicinity of the reference point. The plurality of coil antennas are connected in parallel to the drive device. Magnetic field signal generation system.

8. A mobile device that receives magnetic field signals generated by the aforementioned plurality of coil antennas, The system further includes a processing unit that determines, based on magnetic field signals received by the mobile device, whether or not the mobile device has entered a communication area including the plurality of coil antennas. A magnetic field signal generation system according to one of claims 1 to 7.

9. A mobile device that receives magnetic field signals generated by the aforementioned plurality of coil antennas, The system further comprises a processing unit that calculates the distance of the mobile device to a reference plane based on a magnetic field signal received by the mobile device, A magnetic field signal generation system according to one of claims 2 to 4.

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