JP5588492B2 - Communication device - Google Patents

Description

  The present invention relates to a communication device using a leaky coaxial cable.

  The radiated wave from the leaky coaxial cable (LCX) is radiated at a radiation angle θ in the negative direction toward the incident end side or in the positive direction toward the terminal end side with respect to the normal line of the LCX. A radiation wave has a plurality of radiation modes. Each radiation mode is called an m-th order radiation mode. The radiation angle θm of the m-th order radiation mode is calculated from the slot pitch, the relative dielectric constant of the LCX insulator, and the wavelength of the frequency used (see Non-Patent Document 1).

  When communication such as a wireless LAN is performed in a relatively narrow space such as a conference room, LCX is used as a wireless LAN antenna. At that time, it has been proposed to arrange the LCX in storage grooves formed on the upper and rear surfaces of the conference room desk (see Patent Document 1). The material of the desk is a lot of dielectrics such as wood and plastic, so if the input power to the LCX is large, the radiated wave from the LCX will radiate to the lower side through the desk as well as the desk top and horizontal direction. Is done. Therefore, there is a risk that electromagnetic waves including secret information may leak from the upper floor, adjacent rooms, and windows to the outside or the lower floor.

JP 2011-244194 A

Toshihiko Kishimoto and Shin Sasaki “LCX Communication System” The Institute of Electronics and Communication, published on August 20, 1982

  In order to prevent information leakage, it is only necessary to reduce the input power to the LCX. To that end, it is necessary to add a new component such as an attenuator between the transmitter and the LCX. Alternatively, it is necessary to provide a shielding effect by packing metal on the ceiling, wall surface, and floor surface of the conference room. In addition, about the leak from a window, it was necessary to replace | exchange general glass for the shield glass etc. with an electromagnetic wave shielding effect.

  In view of the above problems, an object of the present invention is to provide a communication device capable of preventing communication information leakage and ensuring communication security.

  According to one aspect of the present invention, a linear center conductor, an insulator covering the center conductor, an outer conductor covering the center conductor with the insulator interposed therebetween, and a sheath covering the outer periphery of the outer conductor are provided along the axial direction. A plurality of slots are provided in the outer conductor at a constant pitch, a leaky coaxial cable extending in the axial direction from one end to the other end where signals are supplied, and a leaky coaxial cable are housed inside and extended in the axial direction And a metal shield box having an opening.

  In one embodiment of the present invention, it is desirable that a sheet that absorbs radiation waves from the leaky coaxial cable be provided on the inner surface of the shield box. It is desirable that the shield box has a lid that covers the opening and reduces the intensity of the radiated wave from the leaky coaxial cable. The lid is preferably an electromagnetic wave absorbing plate or a metal plate having a plurality of holes.

  Furthermore, it is desirable to provide a table in which a shield box is arranged on the top plate with the opening portion facing upward, and the table is provided in contact with the opening portion on the top plate and stores a lid slid from the opening portion. It is desirable to have The storage portion may store another lid having a shielding effect that reduces the intensity of the radiated wave from the leaky coaxial cable.

  Moreover, it is desirable to provide a rotation mechanism provided on one end side of the leaky coaxial cable and exposing the leaky coaxial cable from the opening of the shield box. Further, a plurality of shield boxes in which leaky coaxial cables are housed may be installed.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the communication apparatus which can prevent information leakage and can ensure communication security.

It is the schematic which shows an example of the communication apparatus which concerns on embodiment of this invention. It is the schematic which shows the AA cross section of the communication apparatus shown in FIG. It is the schematic which shows the BB cross section of the communication apparatus shown in FIG. It is the schematic which shows an example of LCX used for the communication apparatus which concerns on embodiment of this invention. It is the side surface schematic diagram which shows an example of the measurement system of the coupling loss distribution of LCX. FIG. 6 is a schematic top view of the measurement system shown in FIG. 5. It is a figure which shows an example of the coupling loss distribution of LCX in the horizontal direction in x = 0.25m. It is a figure which shows the coupling loss distribution in CC cross section of FIG. It is a figure which shows the coupling loss distribution in the DD cross section of FIG. It is a figure which shows an example of the coupling loss distribution in the horizontal direction in x = 0.25m of the communication apparatus shown in FIG. It is a figure which shows the coupling loss distribution in the EE cross section of FIG. It is a figure which shows the coupling loss distribution in the FF cross section of FIG. It is a cross-sectional schematic diagram which shows the other example of the communication apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the coupling loss distribution in the horizontal direction of the communication apparatus shown in FIG. It is a figure which shows the coupling loss distribution in the GG cross section of FIG. It is a figure which shows the coupling loss distribution in the HH cross section of FIG. It is the schematic which shows the other example of the lid | cover used for the communication apparatus which concerns on embodiment of this invention. It is the schematic which shows the II cross section of the lid | cover shown in FIG. It is a figure which shows an example of the relationship between the diameter of the hole provided in the lid | cover shown in FIG. 17, and a shielding effect. It is a figure which shows an example of the coupling loss distribution in the horizontal direction in x = 0.25m of the communication apparatus using the lid | cover shown in FIG. It is a figure which shows the coupling loss distribution in the JJ cross section of FIG. It is a figure which shows the coupling loss distribution in the KK cross section of FIG. It is the schematic which shows the other example of the communication apparatus which concerns on embodiment of this invention. It is the schematic which shows the LL cross section of the communication apparatus shown in FIG. It is a plane schematic diagram which shows an example of the communication apparatus which concerns on the modification of embodiment of this invention. FIG. 26 is a schematic side view of the communication device shown in FIG. 25. It is the schematic explaining operation | movement of the rotation mechanism of the communication apparatus shown in FIG. FIG. 26 is a diagram showing an example of a coupling loss distribution in the horizontal direction at x = 0.25 m when the LCX of the communication device shown in FIG. 25 is rotated vertically. It is a figure which shows the coupling loss distribution in the MM cross section of FIG. It is a figure which shows the coupling loss distribution in the NN cross section of FIG. It is a figure which shows an example of the coupling loss distribution in the horizontal direction in x = 0.25m of the communication apparatus which concerns on other embodiment of this invention. It is a figure which shows the coupling loss distribution in the OO cross section of FIG. It is a figure which shows the other example of the coupling loss distribution in the horizontal direction in x = 0.25m of the communication apparatus which concerns on other embodiment of this invention. It is a figure which shows the coupling loss distribution in the PP cross section of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  The following embodiments of the present invention exemplify apparatuses and methods for embodying the technical idea of the present invention. The technical idea of the present invention is based on the material and shape of component parts. The structure, arrangement, etc. are not specified below. The technical idea of the present invention can be variously modified within the technical scope described in the claims.

  As shown in FIG. 1, the communication device according to the embodiment of the present invention includes LCX 3, shield box 5, and table 40. The feeding portion 7 is connected to the start end portion of the LCX 3 via an approach cable 9 such as a coaxial cable. For example, a 50Ω terminator 4 having the same impedance as that of the LCX 3 is connected to the termination of the LCX 3 to prevent reflection. The LCX 3 is housed inside the shield box 5. The shield box 5 is disposed on the table 40.

  As shown in FIGS. 2 and 3, the shield box 5 is disposed on the top plate 42 of the table 40 with the opening facing upward. The opening of the shield box 5 extends in the axial direction of the LCX 3. A sheet 50 that absorbs radiation waves from the LCX 3 is provided on the inner surface of the shield box 5.

  For example, the shield box 5 is made of a metal such as copper having a thickness Tc of about 0.5 mm, has a length Lc of about 1.1 m, a width Wc of about 50 mm, and a depth Dc of about 50 mm. The material of the table 40 is a dielectric such as wood or resin, and the height to the top plate 42 is about 1 m. The top plate 42 has a length Lt of about 3 m and a width Wt of about 1.5 m. The shield box 5 is disposed substantially at the center of the top plate 42 with the length direction of the shield box 5 parallel to the length direction of the table 40.

  As illustrated in FIG. 4, the LCX 3 includes a center conductor 10, an insulator 12, an outer conductor 14, and a sheath 16. The center conductor 10 extends in the axial direction from the start end to the end where the high-frequency signal is supplied from the power supply unit 7. The insulator 12 is provided so as to cover the central conductor 10. The outer conductor 14 is provided so as to cover the central conductor 10 with the insulator 12 interposed therebetween. The sheath 16 is provided so as to cover the outer periphery of the outer conductor 14.

  As shown in FIG. 4, the outer conductor 14 is provided with a plurality of slots 18 in a zigzag manner at a constant pitch along the axial direction (z-axis) of the LCX. For example, one of the plurality of slots 18 adjacent to each other is a first slot and the other is a second slot. The first slots are arranged at a pitch P inclined at an acute angle α with respect to the axial direction. The second slots are inclined at an obtuse angle β with respect to the axial direction, and are provided at intervals of ½ of the pitch P with respect to the first slots. The angles α and β are complementary to each other.

  For example, the LCX 3 has a central conductor 10 made of copper wire having a diameter of 2 mm, an insulator 12 made of foamed polyethylene having a diameter of 5 mm, an outer conductor 14 made of copper foil having a thickness of 0.01 mm, and a sheath 16 having an outer diameter of 7 mm. Used. The length of LCX3 is about 1 m. The LCX 3 used in the embodiment of the present invention is a backfire antenna, and the radiation intensity from the LCX 3 is determined by the shape of the slot 18 and the like. The radiation intensity is set to a normal level, and the shape of the slot 18 is determined so that the coupling loss Lc at a position 1.5 m away from the LCX 3 is approximately 60 dB. The radiation angle is designed to be about 30 degrees, that is, about -30 degrees on the starting end side of the LCX3.

  As shown in FIGS. 5 and 6, the LCX 3 having a length of about 1 m was installed on the top plate 42 of the table 40 in the anechoic chamber 30 and the coupling loss distribution was measured. In the anechoic chamber 30, the axial direction of LCX3 is the z axis, the height direction with respect to LCX3 is the x axis, and the horizontal direction with respect to LCX3 is the y axis. It arrange | positions so that the start end part of LCX3 may be located in z = 1m-2m. A power feeding unit 7 provided outside the anechoic chamber 30 is connected to the start end of the antenna via an approach cable 9. As the receiving antenna 20, for example, a half-wave standard dipole antenna is disposed directly above the antenna. The receiving antenna 20 is connected via an approach cable 22 to a receiving unit 24 provided outside the anechoic chamber 30.

  A signal of input power Pin with a frequency of 2.4 GHz is supplied from the power feeding unit 7 to the start end of the antenna, and a radiated wave from the antenna is received by the receiving antenna 20. The reception unit 24 detects the reception power Pout of the radiated wave. The coupling loss Lc is calculated by the following equation.

Lc = -10 log (Pout / Pin) (dB) (1)

The receiving antenna 20 is changed from −2 to 2 m in the horizontal (y) direction and from −1 to 2 m in the height (x) direction and the position in the z-axis direction from −1 to 3 m from the LCX 3. The distribution of radiation intensity Lc was measured.

  7, 8 and 9 show the measurement results of the coupling loss distribution. The positions at which the coupling loss Lc is 55 dB, 60 dB, 65 dB, and 70 dB are indicated by a one-dot chain line, a solid line, a broken line, and a dotted line, respectively. As shown in FIGS. 7 to 9, the coupling loss Lc at a position 1.5 m away from the LCX 3 in the horizontal direction and the height direction is about 60 dB as designed. At a position 0.5 m away from LCX3, the coupling loss Lc is reduced by about 5 dB to about 55 dB.

  The radiation from the LCX 3 is strongly distributed in the direction where the radiation angle is about −30 degrees as shown in FIGS. Further, as shown in FIGS. 8 and 9, the radiation is strongly distributed not only above the top plate 42 but also on the floor surface side. Thus, it can be seen that there is strong radiation in all directions centering on LCX3. Therefore, in the structure of the conventional communication device in which the LCX 3 is mounted on the table 40 or embedded, electromagnetic wave leakage occurs through the ceiling, wall, window, or floor to the upper floor, adjacent rooms, outdoors, or downstairs. There is a risk of doing.

  Using the communication apparatus shown in FIG. 1, the coupling loss distribution was measured in the anechoic chamber 30 in the same arrangement as in FIGS. 10, FIG. 11 and FIG. 12 show the measurement results of the coupling loss distribution. As shown in FIGS. 10 to 12, it can be seen that the radiated waves are strongly distributed on the ceiling side and the horizontal direction as in the conventional case, but are very weak on the floor side.

  As described above, in the embodiment, since the LCX 3 is housed inside the metal shield box 5, radiation to the floor surface side can be weakened by the shielding effect of the shield box 5. As a result, it is possible to avoid the risk of electromagnetic leakage to the downstairs side.

  In addition, the sheet | seat 50 is provided in the inner surface of the shield box 5 so that the radiated wave from LCX3 may reflect in the shield box 5, and the electromagnetic field intensity around the table 40 may not become unstable. For the sheet 50, for example, an electromagnetic wave absorbing material such as a flame retardant special rubber having a thickness of about 0.75 mm and filled with magnetic metal powder is used. As the electromagnetic wave absorber used for the sheet 50, a magnetic metal such as iron, a magnetic material such as ferrite, and a rubber mixed with powder of at least one filler among conductors such as carbon can be used.

  As shown in FIG. 13, the opening of the shield box 5 may be covered with a lid 52 made of an electromagnetic wave absorber similar to that of the sheet 50 as a communication device. For the lid 52, for example, an electromagnetic wave absorbing material having a shielding effect of about 5 dB is used.

  Using the communication device shown in FIG. 13, the coupling loss distribution was measured in the anechoic chamber 30 shown in FIGS. FIG. 14, FIG. 15 and FIG. 16 show the measurement results of the coupling loss distribution. As shown in FIGS. 14 to 16, it can be seen that the intensity of the radiation wave on the ceiling side or in the horizontal direction is reduced by about 5 dB compared to the conventional case by the lid 52. It can be seen that there is almost no radiation on the floor side, similar to the communication device shown in FIG.

  Thus, in the communication apparatus shown in FIG. 13, the intensity of the radiated wave in the ceiling or in the horizontal direction can be reduced. As a result, the risk of leakage of confidential information due to electromagnetic wave leakage can be further reduced. As the lid 52, an electromagnetic wave absorbing material having a shielding effect of about 5 dB is used. However, the shielding effect may be arbitrarily changed according to the thickness of the lid 52, the type of filler, the filling amount, or the like, or another material having a shielding effect may be used.

  For example, a metal plate having a plurality of holes 54 may be used as the lid 52a as shown in FIGS. The lid 52a is made of, for example, copper having a length of about 1 m, a width of about 50 mm, and a thickness of about 0.5 mm, and holes 54 having a diameter of about 30 mm are arranged at a pitch of about 31 mm. About the shielding effect of the metal plate with a hole, it can calculate with the following formula | equation (For example, "Mounting and structure technology in a DSM-R apparatus", FUJITSU DENSO REVIEW, Vol.16, December, 2012, Vol. .10, No. 1).

S = 32 (t / g) + 3.8 + 20 log (g ² D / d ³ ) (dB) (2)

Here, S is the shielding effect, t is the thickness of the metal plate, g is the hole diameter, D is the square root of the area of the metal plate, and d is the pitch of the holes.

  FIG. 19 shows the result of calculating the shielding effect using the formula (2) when the size of the metal plate is 1000 mm × 50 mm, the thickness is 0.5 mm, the hole pitch is 31 mm, and the hole diameter is changed. . As shown in FIG. 19, the shielding effect is calculated to be about 20 dB in the lid 52a in which the diameter of the hole 54 is about 30 mm.

  Using the lid 52a in the communication apparatus shown in FIG. 1, the coupling loss distribution was measured in the anechoic chamber 30 shown in FIGS. 20, 21 and 22 show the measurement results of the coupling loss distribution. As shown in FIGS. 20-22, it turns out that the intensity | strength of the radiation wave of a ceiling side or a horizontal direction is reduced about 20 dB compared with the past by the lid | cover 52a. It can be seen that there is almost no radiation on the floor side, similar to the communication device shown in FIG.

  As described above, in the communication apparatus using the lid 52a shown in FIG. 17, the intensity of the radiation wave in the ceiling side or in the horizontal direction can be greatly reduced. As a result, the risk of leakage of confidential information due to electromagnetic wave leakage can be further reduced. Although the shielding effect of the lid 52a is about 20 dB, the shielding effect is not limited. For example, the shielding effect may be arbitrarily changed depending on the thickness of the lid 52a, the diameter and pitch of the holes 54, and the like.

  The lids 52 and 52a may be slidable to open and close the opening of the shield box 5. For example, as shown in FIGS. 23 and 24, lids 52 and 52a are stored in storage portions 58 and 58a provided on the top plate 42 in contact with the opening of the shield box 5, respectively. For example, the lid 52 stored in the storage unit 58 can be slid using the handle 56 so as to cover the opening of the shield box 5. Moreover, the lid | cover 52a accommodated in the accommodating part 58a can be slid so that the opening part of the shield box 5 may be covered using the handle 56a. Therefore, it becomes possible to change the radiation intensity from LCX3.

  For example, when it is desired to increase the radiation intensity, the lids 52 and 52a may be accommodated in the respective accommodating portions 58 and 58a and the opening of the shield box 5 may be opened. When it is desired to reduce the radiation intensity, for example, if the lid 52 is slid to cover the opening of the shield box 5, the radiation intensity can be reduced by about 5 dB. Further, if the lid 52a is slid to cover the opening of the shield box 5, the radiation intensity can be reduced by about 20 dB. As described above, by using a structure in which the lids 52 and 52a are slidable, the risk of leakage of secret information due to electromagnetic wave leakage can be appropriately suppressed. The number of lids is not limited to two. For example, a structure using any one of the lids 52 and 52a may be used. In this case, it is sufficient to provide one storage unit. Three or more lids may be used. In this case, the storage unit may have a multistage structure.

(Modification)
As shown in FIGS. 25 and 26, the communication device according to the modification of the embodiment of the present invention includes a rotation mechanism 71 that rotates the LCX 3 relative to the shield box 5. The LCX 3 is accommodated in the support tube 70. The rotation mechanism 71 includes a support column 72 having one end fixed to the shield box 5, a rotation shaft 74 provided at the other end of the support column 72, and a connection tube 76 that connects the support tube 70 and the rotation shaft 74. The rotation mechanism 71 is provided in the vicinity of the start end of the LCX 3, for example, the connector 78 that connects the LCX 3 and the approach cable 9. By operating the rotation mechanism 71, the LCX 3 can be set at an arbitrary angle from the horizontal position to the vertical position. The support tube 70 is used to support the LCX 3 in a straight line, but other than the tube may be used as long as the LCX 3 can be supported in a straight line.

  The modification of the embodiment is different from the embodiment in that a rotation mechanism 71 is provided at one end of the LCX 3. Other configurations are the same as those in the embodiment, and thus redundant description is omitted.

  When the LCX 3 is arranged horizontally, the radiated wave is radiated strongly in the ceiling direction and the horizontal direction. However, there is a case where it is desired to secure a communication area by concentrating only on conference participants, that is, only on the conference table. In such a case, as shown in FIG. 27, the LCX 3 may be rotated to make it vertical, for example. As described above, the radiation from the LCX 3 is strongly distributed in the direction where the radiation angle is about −30 degrees. Therefore, the radiated wave is radiated toward the top surface of the top plate 42 of the table 40 as shown in FIGS. 28, 29, and 30. Therefore, by making the LCX 3 vertical, the communication area can be concentrated on the upper portion of the table 40, and radiation to the ceiling side or the floor surface side can be reduced. As a result, the risk of leakage of secret information due to electromagnetic wave leakage can be kept low.

  Thus, in the communication apparatus according to the modification of the embodiment, the LCX 3 can be rotated at an arbitrary angle from horizontal to vertical, and the communication area can be changed. For example, if the LCX 3 is used horizontally, a communication area is secured above the table 40 and in the horizontal direction. If the LCX 3 is used vertically, the communication area is limited to the upper side of the table 40. In addition, if the LCX 3 is used with an inclination, a communication area intermediate between the communication areas at the horizontal and vertical positions can be set.

(Other embodiments)
Although the embodiments of the present invention have been described as described above, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  As shown in FIG. 31, for a long table 40 having a length of about 5 m, a width of about 1.5 m, and a height of about 1 m, a plurality of, for example, a plurality of terminators 4 and 4a are arranged in the longitudinal direction so as to mate each other. Two 1 m LCXs 3 and 3a are arranged with a 1 m gap. The LCX 3a is housed inside the shield box 5a. The LCXs 3 and 3a are connected to the distributor 80 via approach cables 9a and 9b, respectively. The distributor 80 is connected to the power feeding unit 7 via the approach cable 9. As shown in FIGS. 31 and 32, a communication area corresponding to the long table 40 can be set by arranging a plurality of LCXs 3 and 3a.

  Further, the rotation mechanisms shown in FIGS. 25 and 26 may be provided in each of the LCXs 3 and 3a. As shown in FIGS. 33 and 34, when the LCXs 3 and 3a are rotated vertically, a communication area can be set on the upper portion of the long table 40. Alternatively, an arbitrary communication area may be set by using only one of the LCXs 3 and 3a as vertical and using the other as horizontal.

  As described above, the present invention naturally includes various embodiments that are not described herein. Accordingly, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

3. Leakage coaxial cable (LCX)
DESCRIPTION OF SYMBOLS 5 ... Shield box 10 ... Center conductor 12 ... Insulator 14 ... Outer conductor 16 ... Sheath 18 ... Slot 40 ... Table 42 ... Top plate 50 ... Sheet 52 ... Lid 54 ... Hole 58 ... Storage part 71 ... Rotation mechanism

Claims (10)

A linear center conductor, an insulator covering the center conductor, an outer conductor covering the center conductor with the insulator sandwiched therebetween, and a sheath covering the outer periphery of the outer conductor, and fixed to the outer conductor along the axial direction A leaky coaxial cable extending in the axial direction from one end to the other end where a signal is supplied, with a plurality of slots provided at a pitch of
A metal shield box that houses the leaky coaxial cable and has an opening extending in the axial direction;
A communication apparatus comprising:   The communication apparatus according to claim 1, wherein a sheet that absorbs radiation waves from the leaky coaxial cable is provided on an inner surface of the shield box.   The communication apparatus according to claim 1, wherein the shield box includes a lid that covers the opening and reduces the intensity of a radiated wave from the leaky coaxial cable.   The communication device according to claim 3, wherein the lid is an electromagnetic wave absorbing plate.   The communication device according to claim 3, wherein the lid is a metal plate having a plurality of holes.   The communication apparatus according to claim 1, further comprising a table in which the opening is directed upward and the shield box is arranged on a top plate. A table in which the shield box is arranged on a top plate with the opening facing upward,
The said table is provided in the said top plate in contact with the said opening part, and has a storage part which accommodates the said lid | cover slid from the said opening part, The any one of Claims 3-5 characterized by the above-mentioned. Communication equipment.   The communication device according to claim 7, wherein the storage unit stores another lid having a shielding effect for reducing the intensity of the radiated wave from the leaky coaxial cable, which is different from the lid.   The communication apparatus according to claim 1, further comprising a rotation mechanism that is provided on one end side of the leaky coaxial cable and exposes the leaky coaxial cable from the opening of the shield box. .   The communication device according to any one of claims 1 to 9, wherein a plurality of the shield boxes in which the leaky coaxial cable is housed are installed.

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