JP5657431B2 - Communications system - Google Patents

Description

  The present invention relates to a communication system using a leaky transmission line, and more particularly to a communication system that performs wireless communication between leaky transmission lines.

  Conventionally, as a leaky transmission line, for example, a leaky coaxial cable (LCX: Leaky Coaxial Cable) has been proposed and used as a transmission / reception antenna in a wireless communication system. LCX, for example, is laid along the train track for the purpose of wireless communication between the train and the ground, and for the purpose of communication by fire radio and police radio between the subway premises and the underground shopping center. And will be laid in the underground mall. In addition, wireless communication systems represented by mobile phones and wireless LANs are rapidly expanding because anyone can use a communication network anytime, anywhere.

  In addition, as shown in FIG. 12, a wireless LAN system can be used in controlling a crane 64 that moves material in a factory such as an ironworks. In this wireless LAN system, LCXs 52a and 52b are attached along the rail 63 along which the crane 64 moves, and a planar antenna 62 is attached to the side surface of the crane 64 facing the LCXs 52a and 52b. One end of each of the LCXs 52 a and 52 b is connected to the distributor 51, and the distributor 51 is connected to the access point 50. And the crane 64 is controlled by transmitting / receiving the wireless LAN signal between LCX52a, 52b and the planar antenna 62 (refer nonpatent literature 1 and 2).

JP 2009-171458 A

Tomonori Sugiyama and two others, “Leaked coaxial cable wireless LAN that enables stable communication in steelworks with many metal structures”, [online], 2009, Toshiba review, [September 3, 2010] , Internet (URL: http://www.toshiba.co.jp/tech/review/2009/11/64_11pdf/f05.pdf) "Leaked cable (LCX) wireless LAN system", [online], Toshiba Tec Corporation, Internet (URL: http://www.tec.jp/catalog/detail/lcxlan.htm)

  In the wireless LAN system shown in Non-Patent Document 1 and FIG. 12, LCXs 52a and 52b and a planar antenna 62 are used as transmission / reception antennas. Here, the directivity of the LCX 52a and the planar antenna 62 will be examined. As shown in FIG. 14A, the directivity half-value angle θ with respect to the vertical polarization in the plane including the LCX 52a is about 10 degrees (see FIG. 7 of Japanese Patent Laid-Open No. 2009-171458). The “directivity half-value angle with respect to vertical polarization” is an angle at which the power of the radiated wave becomes half of the peak value. The directivity region dd, which is a region within the directivity half-value angle, forms a conical radiation beam in the direction of the radiation angle α with the LCX 52a as an axis. The radiation angle θ is determined by the pitch of the holes provided in the outer conductor of the LCX and the wavelength of the electromagnetic wave propagating through the LCX (Toshihiko Kishimoto, one other person, “LCX communication system”, Corona, August 20, 1982) Issue). On the other hand, as shown in FIG. 14B, in the directivity region fd of the planar antenna 62, the directivity half-value angle β of the planar antenna 62 is larger than the LCX 52a and is in the range of 60 degrees to 75 degrees. (Buffalo Co., Ltd., flat antenna catalog for wireless LAN, URL: http://buffalo.jp/products/catalog/network/wle-2da/, and Maspro Electric Corporation, flat antenna catalog for wireless LAN, URL: http: // See www.maspro.co.jp/pdfview/manual_pdf/4843.pdf).

  In the wireless LAN system of FIG. 12, as shown in FIG. 13, the LCX 52a and the planar antenna 62 are attached so that the directivity areas dd and fd coincide with each other. Therefore, the radio wave SL emitted as a sharp radiation beam from the LCX 52a is received by the planar antenna 62 as a direct wave. However, when a wireless LAN system is attached to a factory such as a steel mill, radio waves from the LCXs 52a and 52b are reflected by the metal bodies 65a and 65b existing in the space, as shown in FIG. Thereby, a large number of reflected waves MP1, MP2, that is, multipath waves are generated.

  Since the directivity half-value angle β of the planar antenna 62 is large, many multipath waves MP1 and MP2 are received in addition to the radio wave SL from the LCXs 52a and 52b. As a result, communication failure may occur, communication may become impossible, and the crane 64 may become uncontrollable.

  Further, when another wireless LAN system exists in the vicinity, the planar antenna 62 receives radio waves from the other wireless LAN system. Therefore, in the same manner as in the case of the multipath waves MP1 and MP2, a reception failure may occur, resulting in communication failure and crane 64 control failure.

  FIG. 16 is a cross-sectional view of the directivity regions dd and fd along the line CC of FIG. The directivity region dd is formed by the LCXs 52a and 52b and has a substantially ring shape. The directivity region fd is formed by the planar antenna 62 and has a substantially circular shape. In the part fddd where the directivity region dd and the directivity region fd overlap, the planar antenna 62 receives the radio wave SL emitted from the LCX 52a as a direct wave. In the area excluding the overlapping part fddd in the directivity area fd, multipath waves and radio waves from other wireless LAN systems are received.

  In response to these technical problems, the mobile communication system described in Patent Document 1 uses LCX instead of the planar antenna 62 as an antenna mounted on a mobile body corresponding to the crane 64 in FIG. Yes. That is, the LCX is adopted as both the stationary antenna arranged along the moving direction of the moving body (rail 63 in FIG. 12) and the antenna mounted on the moving body (crane 64 in FIG. 12). Wireless communication is performed. By reducing the directivity half-value angle θ with respect to the vertical polarization and narrowing the directivity region dd, it becomes difficult to receive multipath waves and radio waves from other wireless LAN systems, and communication failures can be suppressed. .

  However, Patent Document 1 does not describe a necessary length of LCX, an appropriate distance between LCXs, or an allowable position error. Actually, when implementing a communication system that performs wireless communication between LCXs, the required length of LCX, the appropriate interval between LCXs, and the allowable position error are obtained by trial and error. Therefore, in actuality, when constructing the mobile communication system described in Patent Document 1, it is necessary to conduct a long-term verification experiment in the field, and it is also necessary to stop the operation in the field. It will be expensive.

  The present invention has been made in view of the above problems, and an object of the present invention is to suppress communication failure due to multipath waves and radio waves of other wireless LAN systems in a communication system that performs wireless communication between leaky transmission lines. It is.

  Another object of the present invention is to eliminate the need for a long-term verification experiment and an on-site operation stop associated therewith when implementing a communication system that performs wireless communication between leaky transmission lines.

  One aspect of the present invention is a communication system in which a base station and a communication terminal, each using a leaky transmission line as an antenna, communicate with each other wirelessly, the base station including a first leaky transmission line forming a line segment, And a communication terminal comprising a second leaky transmission line forming a part. In one plane including the entire first leaky transmission line and at least a part of the second leaky transmission line, the inclination angle of the second leaky transmission line and the first leaky transmission line is −5 degrees to 5 degrees. It is. The twist angle of the second leaky transmission line in the direction perpendicular to the one plane is −5 degrees or more and 5 degrees or less. The length of the second leaky transmission line is 5 m or less.

  In one aspect of the present invention, the length of the second leaky transmission line may be 1 m or longer, and the length of the first leaky transmission line may be equal to or longer than the length of the second leaky transmission line.

  In one aspect of the present invention, the interval between the first leaky transmission line and the second leaky transmission line may be 1 m or less.

  In one embodiment of the present invention, the communication system is provided on the opposite side of the side where the first leaky transmission line and the second leaky transmission line are opposed, and is directed to the radio wave transmitted from the leaky transmission line and the leaky transmission line. You may further provide the electromagnetic wave absorber which absorbs an electromagnetic wave.

  In one aspect of the present invention, the inclination angle between the second leaky transmission line and the first leaky transmission line is within one plane including the entire first leaky transmission line and at least part of the second leaky transmission line. The allowable range may be narrower than the allowable range of the twist angle of the second leaky transmission line in the direction perpendicular to the one plane.

  As described above, according to the present invention, the inclination angle of the second leaky transmission line and the first leaky transmission line is −5 degrees to 5 degrees, and the twist angle is −5 degrees to 5 degrees. Yes, because the length of the second leaky transmission line is 5 m or less, in a communication system that performs wireless communication between leaky transmission lines, communication failure due to multipath waves and radio waves of other wireless LAN systems is suppressed. Can do.

  Further, according to the present invention, when implementing a communication system that performs wireless communication between leaky transmission lines, it is possible to eliminate the need for long-term verification experiments and on-site operation stoppage associated therewith.

FIG. 1 is a schematic diagram showing an overall configuration of a communication system according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing the first leaky transmission line 21 and the second leaky transmission line 32 with the radiation directions facing each other. FIG. 3 is a cross-sectional view showing the directivity regions D1 and D2 along the line BB in FIG. FIG. 4 is a schematic diagram for explaining a change in directivity due to the length of the second leaky transmission line 32. FIG. 4A shows a case where the length L _S of the second leaky transmission line 32 is short. FIG. 4B shows a case where the length L _L of the second leaky transmission line 32 is long. FIG. 5 is a schematic diagram for defining an inclination angle φ of the second leaky transmission line 32 in a plane including the first leaky transmission line 21 and the second leaky transmission line 32 arranged in parallel. FIG. 6 is a graph showing a change in the coupling value Lc when the inclination angle φ is changed from 0 degree in the positive direction and the negative direction, and FIG. 6A shows the length of the second leaky transmission line 32. FIG. 6B shows a case where the length of the second leaky transmission line 32 is 3 m. Figure 7 is a graph showing the relationship between the length and the distance Y and stable communication inclination angle phi _SA of the second leaky transmission line 32. FIG. 8 is a schematic diagram for defining a twist angle δ of the second leaky transmission line 32 in a direction perpendicular to a plane including the first leaky transmission line 21 and the second leaky transmission line 32 arranged in parallel. FIG. FIG. 9 is a graph showing the relationship between the length and interval Y of the second leaky transmission line 32 and the stable communication twist angle δ _SA . FIG. 10 is a cross-sectional view for explaining the degree of change in the coupling value Lc according to the amount of change in the inclination angle φ and the torsion angle δ. FIG. 10A shows the case where the inclination angle φ is changed. (B) shows a case where the twist angle δ is changed. FIG. 11A is a cross-sectional view showing radio wave absorbers 44 and 43 and metal plates 42 and 41 that absorb radio waves transmitted from the leaky transmission lines 21 and 32 and radio waves directed to the leaky transmission lines 21 and 32, respectively. FIG. 11B is a cross-sectional view showing the directivity regions D1 and D2 formed by the leaky transmission lines 21 and 32 of FIG. FIG. 12 is a schematic diagram illustrating an example in which a wireless LAN system is used in the control of the crane 64 that moves material in a factory such as a steel mill. FIG. 13 is a schematic diagram showing the attachment direction of the LCX 52a and the planar antenna 62. As shown in FIG. FIG. 14A is a schematic diagram showing the directivity of the LCXs 52 a and 52 b, and FIG. 14B is a schematic diagram showing the directivity of the planar antenna 62. FIG. 15 is a schematic diagram for explaining a communication failure due to a multipath wave. FIG. 16 is a cross-sectional view of the directivity regions dd and fd along the line CC of FIG.

  Embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same parts are denoted by the same reference numerals.

<Configuration of communication system>
First, an overall configuration of a communication system according to an embodiment of the present invention will be described with reference to FIG. A communication system 10 according to an embodiment of the present invention includes a radio base station (base station) 20 and a mobile unit (communication terminal) 30. The radio base station 20 includes a first leaky transmission line 21 that functions as an antenna. One end of the first leaky transmission line 21 is connected to the radio base station 20, and the other end is terminated by a terminator (termination resistor) 22. The first leaky transmission line 21 forms a line segment except for bending due to its own weight and a bent portion due to installation error. Further, the first leaky transmission line 21 extends in parallel to the linear movement path RT of the moving body 30.

  The moving body 30 moves linearly along the movement route RT, and includes a communication terminal 31 that appropriately communicates with the radio base station 20, a second leaky transmission line 32 that functions as an antenna, and a second And a terminator (termination resistor) 33 for terminating the leaky transmission line 32.

  The extension direction of the second leaky transmission line 32 from the communication terminal 31 is opposite to the extension direction of the first leaky transmission line 21 from the radio base station 20. The second leaky transmission line 32 forms a line segment and is installed in parallel to the movement path RT. Therefore, the second leaky transmission line 32 and the first leaky transmission line 21 maintain a parallel state in the movable range of the moving body 30. Therefore, the radiation direction of the second leaky transmission line 32 faces the radiation direction of the leaky transmission line portions 21 on both ends. Thereby, the 1st leaky transmission line 21 and the 2nd leaky transmission line 32 in which the radiation direction is directly opposed are strongly coupled to ensure stable communication between the mobile body 30 and the radio base station 20. Can do. For example, as the second leaky transmission line 32 and the first leaky transmission line 21, leaky coaxial cables (LCX) having the same characteristics but different lengths can be applied.

  Here, the parallel degree between the second leaky transmission line 32 and the first leaky transmission line 21 corresponds to an allowable range of an inclination angle and a twist angle between the leaky transmission lines 21 and 32 described later.

  The leaky transmission lines 21 and 32 include a center conductor, an insulator covering the center conductor, an outer conductor disposed around the insulator, and a jacket (sheath) covering the outer conductor. It is configured as a coaxial cable. The material forming the central conductor and the outer conductor of the leaky transmission lines 21 and 32 is generally copper, but aluminum may also be used. As a material forming the insulator, polyethylene or the like is mainly used. The outer conductors of the leaky transmission lines 21 and 32 are provided with slots (elongated openings) periodically in the cable length direction as an electromagnetic wave leakage mechanism. The radiation principle of the leaky transmission lines 21 and 32 is that a part of the electric signal energy transmitted inside the cable radiates to the outside as an electromagnetic wave.

  FIG. 2 shows a directivity region D1 of the first leaky transmission line 21 and a directivity region D2 of the second leaky transmission line 32 corresponding to the radiation direction of FIG. Here, “directivity regions D1 and D2” indicate regions within the directivity half-value angle θ with respect to vertical polarization in a plane including the leaky transmission lines 21 and 32. When the first leaky transmission line 21 and the second leaky transmission line 32 are arranged in parallel, the directivity region D1 of the first leaky transmission line 21 and the directivity region D2 of the second leaky transmission line 32 are Face up. Since the directivity half-value angle θ with respect to the vertical polarization in the plane including the first leaky transmission line 21 and the second leaky transmission line 32 is small, the radio wave OP from the multipath waves MP1 and MP2 and other wireless LAN systems. It becomes difficult to receive.

  FIG. 3 shows directivity regions D1 and D2 along the line BB in FIG. The directivity region D1 is formed by the first leaky transmission line 21, and the directivity region D2 is formed by the second leaky transmission line 32. In the portion D12 where the directivity region D1 and the directivity region D2 overlap, the first leaky transmission line 21 receives the radio wave emitted from the second leaky transmission line 32 as a direct wave. Since the area excluding the overlapping part D12 in the directivity area D2 is narrower than that in the case where the planar antenna 62 shown in FIG. 16 is used, the second leaky transmission line 32 can be a multipath wave or other wireless LAN. It becomes difficult to receive radio waves from the system. That is, the communication system of FIG. 1 can be said to be a system that is more resistant to communication failures than the communication system of FIG.

<Leakage transmission line length, leakage transmission line interval and angle error>
First, with reference to FIG. 4, the change in directivity due to the length of the second leaky transmission line 32 will be described. As shown in FIG. 4 (a), when the length L _S of the second leaky transmission line 32 is short, half-directivity angle theta _S for vertically polarized waves becomes large, the width of the directional region D _S becomes wider . As shown in FIG. 4B, when the length L _{L of} the second leaky transmission line 32 is long, the directivity half-value angle θ _W with respect to the vertical polarization becomes small, and the width of the directivity region D _W becomes narrow. . When the second leaky transmission line 32 becomes longer, the number of openings serving as wave sources included in the second leaky transmission line 32 increases, and the directivity half-value angle θ becomes smaller. In addition, the directivity region D of the second leaky transmission line 32 also changes depending on the distance from the first leaky transmission line 21 . The closer the distance from the first leaky transmission line 21 is, the narrower the width of the directivity region D is. The directivity direction of the leaky transmission lines 21 and 32 changes due to an attachment error of the leaky transmission lines 21 and 32. In order to ensure stable wireless communication, it is desirable to investigate in advance the length of the leaky transmission lines 21, 32, the interval Y between the leaky transmission lines 21, 32, and the mounting accuracy of the leaky transmission lines 21, 32. .

  Next, the length of the second leaky transmission line 32 exerted on the coupling value Lc of the first leaky transmission line 21 and the second leaky transmission line 32 performed by the inventors of the present invention, the first leaky transmission line A description will be given of the results of investigation on the distance between the first leaky transmission line 32 and the tilt angle and the twist angle between the first leaky transmission line 21 and the second leaky transmission line 32.

  With reference to FIG. 5, the inclination angle φ of the second leaky transmission line 32 in the plane including the first leaky transmission line 21 and the second leaky transmission line 32 arranged in parallel will be described. In the xyz orthogonal coordinate system shown in FIG. 5, the first leaky transmission line 21 is arranged on the z axis, and the center of the first leaky transmission line 21 is located at the origin. The second leaky transmission line 32 is arranged in parallel to the first leaky transmission line 21 in the zy plane, the center of the second leaky transmission line 32 intersects the y axis, and its y coordinate is Y. . That is, the interval between the first leaky transmission line 21 and the second leaky transmission line 32 is Y. Although not shown in FIG. 5, an oscillator is connected to one end of the first leaky transmission line 21, and a termination resistor is connected to the other end. A receiver is connected to one end of the second leaky transmission line 32.

  Then, the second leaky transmission line 32 was rotated in the zy plane with the center of the second leaky transmission line 32 as the rotation axis. Changes in the coupling value Lc of the first leaky transmission line 21 and the second leaky transmission line 32 with respect to the rotation angle (hereinafter referred to as “inclination angle”) φ at this time were measured. In addition, it measured about the case where the length of the 2nd leaky transmission line 32 is 1 m, 3 m, and 5 m, respectively. Furthermore, it measured about the case where the space | interval Y of the 1st leaky transmission line 21 and the 2nd leaky transmission line 32 is 0.1 m, 0.5 m, 1 m, and 1.5 m, respectively. The length of the first leaky transmission line 21 is desirably long enough to receive radio waves emitted from the second leaky transmission line 32, and is equal to or longer than the second leaky transmission line 32. It is preferable. Here, the length of the first leaky transmission line 21 is 6 m.

  Further, the coupling value Lc can be obtained from Equation (1) as the ratio of the input power Pin to the first leaky transmission line 21 and the output power Pout from the second leaky transmission line 32. As can be seen from the equation (1), the electromagnetic coupling between the first leaky transmission line 21 and the second leaky transmission line 32 becomes stronger as the coupling value Lc is larger. The unit of the combined value Lc is dB.

      Lc = 10 × log (Pout / Pin) (1)

  FIG. 6 is a graph showing a change in the coupling value Lc when the inclination angle φ is changed from 0 degree in the positive direction and the negative direction. 6A shows a case where the length of the second leaky transmission line 32 is 1 m, and FIG. 6B shows a case where the length of the second leaky transmission line 32 is 3 m. The horizontal axis indicates the inclination angle φ, and the vertical axis indicates the coupling value Lc. The interval Y between the first leaky transmission line 21 and the second leaky transmission line 32 is 1 m.

Here, the state in which a stable coupling value Lc is obtained between the first leaky transmission line 21 and the second leaky transmission line 32 is generally a coupling value that is half the peak coupling value, that is, the coupling value. This is a range from the peak value of 3 dB down to 3 dB. This is called “stable communication range”. The inclination angle φ that gives this stable communication range (hereinafter referred to as “stable communication inclination angle φ _SA ”) was 9 degrees in FIG. 6A and 2 degrees in FIG. 6B.

Figure 7 shows the results of measurement of the stable communication inclination angle phi _SA by changing the length and the distance Y of the second leaky transmission line 32. It can be seen that the longer the length of the second leaky transmission line 32 is, the smaller the distance Y between the second leaky transmission line 32 and the first leaky transmission line 21 is, and the smaller the stable communication inclination angle φ _SA is.

  Next, with reference to FIG. 8, the twist of the second leaky transmission line 32 in the direction perpendicular to the plane including the first leaky transmission line 21 and the second leaky transmission line 32 arranged in parallel. The angle δ will be described. In the xyz orthogonal coordinate system shown in FIG. 8, the first leaky transmission line 21 and the second leaky transmission line 32 are arranged in the same manner as in FIG. 5.

  Then, the second leaky transmission line 32 was rotated in a direction perpendicular to the zy plane with the center of the second leaky transmission line 32 as the rotation axis. A change in the coupling value Lc of the first leaky transmission line 21 and the second leaky transmission line 32 with respect to the rotation angle (hereinafter referred to as “twist angle”) δ at this time was measured. In addition, it measured about the case where the length of the 2nd leaky transmission line 32 is 1 m, 3 m, and 5 m, respectively. Furthermore, it measured about the case where the space | interval Y of the 1st leaky transmission line 21 and the 2nd leaky transmission line 32 is 0.1 m, 0.5 m, 1 m, and 1.5 m, respectively. The length of the first leaky transmission line 21 was 6 m.

FIG. 9 shows the result of measuring the stable communication twist angle δ _SA while changing the length and interval Y of the second leaky transmission line 32. Here, the “stable communication twist angle δ _SA ” is the twist angle δ that gives the stable communication range described with reference to FIG. 6. It can be seen that as the length of the second leaky transmission line 32 becomes longer and the distance Y between the second leaky transmission line 32 and the first leaky transmission line 21 becomes shorter, the stable communication twist angle δ _SA becomes smaller. This tendency was similar to the inclination angle φ.

Comparing the measurement results of FIG. 7 and FIG. 9, it can be seen that the stable communication inclination angle φ _SA is smaller than the stable communication twist angle δ _{SA when} the length and the interval Y of the second leaky transmission line 32 are the same. This is because, as shown in FIG. 10, the area of the region where the directivity region D1 of the first leaky transmission line 21 and the directivity region D2 of the second leaky transmission line 32 overlap has the twist angle δ as a variable. This is because the inclination angle φ changes more rapidly than the case. FIG. 10A shows the directivity region D1 and the directivity region D2 when the tilt angle φ is 0 degree, and the directivity region D2φ1 when the tilt angle φ is 1 degree. When the inclination angle φ is changed, the directivity region D2 moves in the width direction thereof, so that the area of the overlapping region changes rapidly. Therefore, the stable communication inclination angle φ _SA is small. On the other hand, when the twist angle δ is changed, the directivity region D2 is perpendicular to the direction along the circumference of the directivity region D2 or the plane including the first leaky transmission line 21 and the second leaky transmission line 32. The area of the overlapping region does not change suddenly. Therefore, the stable communication torsion angle δ _SA increases.

  Therefore, the inclination angle φ of the second leaky transmission line 32 and the first leaky transmission line 21 is within one plane including the entire first leaky transmission line 21 and at least a part of the second leaky transmission line 32. It is preferable that the allowable range is narrower than the allowable range of the twist angle δ of the second leaky transmission line in the direction perpendicular to the one plane. Thereby, the rapid change of the area of the area | region where the directivity area | region D1 of the 1st leaky transmission line 21 and the directivity area | region D2 of the 2nd leaky transmission line 32 overlap can be suppressed. Therefore, deterioration of communication quality can be suppressed and good radio communication between the radio base station 20 and the mobile object 30 can be ensured.

Then, the length of the second leakage transmission line 32, the distance Y of the leaky transmission line 21 and 32, the appropriate value of the stable communication inclination angle phi _SA and stable communication twist angle [delta] _SA will be described. The wider the stable communication tilt angle φ _SA and the stable communication twist angle δ _SA , the easier it is to receive multipath waves and radio waves from other wireless LAN systems. As described above, the directivity half-value angle β with respect to the vertical polarization in front of the planar antenna 62 is in the range of 60 degrees to 75 degrees. Therefore, if the stable communication tilt angle φ _SA and the stable communication twist angle δ _SA are 50 degrees or less, communication troubles due to multipath waves and radio waves of other wireless LAN systems can be suppressed as compared with the case of the planar antenna 62. Can do.

As can be seen from FIG. 9, in order to set the stable communication twist angle δ _SA to 50 degrees or less, the interval Y between the leaky transmission lines 21 and 32 is set to 1 m or less, and the length of the second leaky transmission line 32 is What is necessary is just to set to 1 m or more. As described above, the length of the first leaky transmission line 21 is desirably long enough to receive the radio wave emitted from the second leaky transmission line 32, and is equal to the second leaky transmission line 32. Or it is preferable that it is more. As the distance Y between the leaky transmission lines 21 and 32 is shortened and the length of the second leaky transmission line 32 is lengthened, the stable communication inclination angle φ _SA and the stable communication twist angle δ _SA are reduced. It can be suppressed more strongly.

When the interval Y between the leaky transmission lines 21 and 32 is set to 1 m or less and the length of the second leaky transmission line 32 is set to 1 m or more, the entire first leaky transmission line 21 and the second leaky transmission line The inclination angle φ of the second leaky transmission line 32 and the first leaky transmission line 21 is not less than −5 degrees and not more than 5 degrees in one plane including at least a part of 32 (yz plane in FIG. 5). desirable. By the inclination angle phi below 5 degrees -5 degrees, as shown in FIG. 7, attaching a second leaky transmission line 32 and the first leakage transmission path 21 within a stable communication inclination angle phi _SA can do. Therefore, deterioration of communication quality can be suppressed and good radio communication between the radio base station 20 and the mobile object 30 can be ensured. At the same time, when implementing a communication system that performs wireless communication between leaky transmission lines, it is possible to eliminate the need for long-term verification experiments and on-site operation stoppages associated therewith.

Furthermore, when the length of the second leaky transmission line 32 is set to 5 m or less, a plane including the entire first leaky transmission line 21 and at least a part of the second leaky transmission line 32 (yz in FIG. 8). The twist angle δ of the second leaky transmission line 32 in the direction perpendicular to the plane is preferably −5 degrees or more and 5 degrees or less. By setting the twist angle δ to -5 degrees or more and 5 degrees or less, as shown in FIG. 9, the second leaky transmission line 32 and the first leaky transmission line 21 are provided within the range of the stable communication twist angle δ _SA. can do. Therefore, deterioration of communication quality can be suppressed and good radio communication between the radio base station 20 and the mobile object 30 can be ensured. At the same time, it is possible to eliminate the need for long-term verification experiments and on-site operation stoppages associated therewith.

(Other embodiments)
As described above, the present invention has been described by way of one embodiment, but it should not be understood that the discussion and drawings that form 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.

  For example, the communication system includes radio wave absorbers 44 and 43 that absorb radio waves transmitted from the leaky transmission lines 21 and 32 and radio waves directed to the leaky transmission lines 21 and 32 as shown in FIG. May be further provided. The radio wave absorber 44 is provided at least on the opposite side of the first leaky transmission line 21 from the side facing the second leaky transmission line 32. In the example of FIG. 11A, radio wave absorption is performed not only on the opposite side of the side facing the second leaky transmission line 32 but also on the entire outer peripheral surface except the side facing the second leaky transmission line 32. A body 44 is arranged. Similarly, the radio wave absorber 43 is provided at least on the opposite side of the second leaky transmission line 32 from the side facing the first leaky transmission line 21. In the example of FIG. 11A, radio wave absorption is performed not only on the opposite side of the side facing the first leaky transmission line 21 but also on the entire outer peripheral surface except the side facing the first leaky transmission line 21. A body 43 is arranged. The radio wave absorbers 44 and 43 are arranged in a fan shape at regular intervals from the outer peripheral surfaces of the leaky transmission lines 21 and 32. The radio wave absorbers 44 and 43 can absorb multipath waves and radio waves of other wireless LAN systems, and can more strongly suppress communication failures.

  Further, metal plates 42 and 41 may be provided on the outer peripheral side surfaces of the radio wave absorbers 44 and 43, respectively. By applying a ground potential to the metal plates 42 and 41, they are used as radio wave shielding metal plates. A communication failure can be more strongly suppressed by reflecting a multipath wave directed to each of the leaky transmission lines 21 and 32 and a radio wave of another wireless LAN system.

  FIG. 11B is a cross-sectional view showing the directivity regions D1 and D2 formed by the leaky transmission lines 21 and 32 of FIG. Since the area excluding the overlapping portion in the directivity area D1 is narrower than that shown in FIG. 3, the second leaky transmission line 32 receives multipath waves and radio waves from other wireless LAN systems. It becomes difficult. That is, the communication system of FIG. 11 can be said to be a system that is more resistant to communication failures than the communication system shown in FIG.

20 Radio base station (base station)
30 Mobile (communication terminal)
21 First leaky transmission line 32 Second leaky transmission line φ Inclination angle δ Torsion angle 43, 44 Wave absorber

Claims (4)

A base station and a communication terminal each using a leaky transmission line as an antenna communicate with each other wirelessly,
The base station comprising a first leaky transmission line forming a line segment;
The communication terminal comprising a second leaky transmission line forming a line segment,
In one plane including the whole of the first leaky transmission line and at least a part of the second leaky transmission line, an allowable range of inclination angles of the second leaky transmission line and the first leaky transmission line is set as the one range. Narrower than the allowable range of the twist angle of the second leaky transmission line in the direction perpendicular to the plane,
In one plane including the entire first leaky transmission line and at least a part of the second leaky transmission line, an inclination angle of the second leaky transmission line and the first leaky transmission line is −2 degrees or more. 2 degrees or less,
The twist angle of the second leaky transmission line in the direction perpendicular to the one plane is not less than −5 degrees and not more than 5 degrees;
The communication system, wherein the length of the second leaky transmission line is 5 m or less.   The length of the second leaky transmission line is 1 m or more, and the length of the first leaky transmission line is more than the length of the second leaky transmission line. Communications system.   The communication system according to claim 1 or 2, wherein an interval between the first leaky transmission line and the second leaky transmission line is 1 m or less.   The radio wave transmitted from the first leaky transmission line or the second leaky transmission line provided on the opposite side of the side where the first leaky transmission line and the second leaky transmission line face each other, and the first The communication system according to any one of claims 1 to 3, further comprising a radio wave absorber that absorbs radio waves directed to one leaky transmission line or the second leaky transmission line.

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