JP2015126341A - Radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology with regard to a radio communication system performing radio communication in a specific space covered with a conductor, for suppressing radio wave's leakage to the external space without stopping radio communication even in a state in which the specific space is opened to the external space by an opening and closing member.SOLUTION: A radio communication system comprises: an antenna unit (10) 10 which is provided in a specific space (SP) covered by a conductor at least on the periphery in the horizontal direction and is composed of one or more antennas for radiating a radio wave in a direction horizontal and along an opening surface which is the specific space's boundary surface to be opened to the external space by an opening and closing member for opening and closing the specific space; and a communication device (20) for transmitting a radio wave by using the antenna unit. A frequency of the radio wave radiated from the antenna unit is set so that a standing wave is formed, along the direction of the radio wave's radiation, in the specific space.

Description

  The present invention relates to a technique for performing wireless communication in a specific space covered with a conductor.

  When performing wireless communication between electronic devices mounted on a vehicle, it is necessary to suppress leakage of radio waves from the opening provided in the metal body to the outside of the vehicle. In particular, when a door, a rear gate, or the like is opened, a large opening is formed, so that leakage of radio waves increases.

  On the other hand, a technique has been proposed in which a loop antenna is used as a transmitting antenna and the loop antenna is arranged around the inner periphery of the vehicle body so that no loop is formed when the door is opened ( For example, see Patent Document 1).

JP 2003-264415 A

However, the above-described conventional technology has a problem in that various functions are restricted because wireless communication is interrupted when the door is opened.
The present invention has been made in view of these problems, and in a wireless communication system that performs wireless communication in a specific space covered with a conductor, wireless communication is performed even when the specific space is opened to an external space by an opening / closing member. It aims at providing the technology which controls the leak of the electromagnetic wave to external space, without stopping.

  The wireless communication system of the present invention includes an antenna unit and a transmitter. The antenna unit is composed of one or more antennas, and is installed in a specific space at least surrounded by a conductor in the horizontal direction, and a boundary of the specific space that is opened to the external space by an opening / closing member that opens and closes the specific space With the surface as an open surface, radio waves are radiated in the horizontal direction and along the open surface. The communication device transmits radio waves using the antenna unit. The frequency of the radio wave radiated from the antenna unit is set to a size that allows a standing wave to be formed in the specific space along the radiation direction of the radio wave.

  According to such a configuration, by forming a standing wave in the radiation direction of the radio wave, leakage of the radio wave in a direction orthogonal to the radiation direction is suppressed. As a result, even when the specific space is opened by the opening / closing member, the open surface formed by the opening / closing member exists in a direction orthogonal to the radiation direction, so that the wireless communication can be performed without stopping the wireless communication. Leakage of radio waves can be suppressed.

  In addition, the code | symbol in the parenthesis described in the claim shows the correspondence with the specific means as described in embodiment mentioned later as one aspect, Comprising: The technical scope of this invention is limited is not.

  In addition to the above-described wireless communication system, the present invention can be realized in various forms such as various structures including the wireless communication system as a constituent element and an antenna arrangement method in a specific space.

It is explanatory drawing which shows the whole structure of the radio | wireless communications system of 1st Embodiment, and arrangement | positioning of each part, (a) is a top view of the vehicle to which a radio | wireless communications system is applied, (b) is a side view. It is a block diagram which shows the whole structure of the communication apparatus which comprises a radio | wireless communications system. It is explanatory drawing which illustrates the distribution state of the standing wave in each radiation mode, (a) is a vertical mode, (b) is a horizontal mode, (c) is a vertical and horizontal mode. It is a flowchart which shows the content of the control which the control part of a communication apparatus performs. It is a flowchart showing the detail of an excitation mode setting process. It is explanatory drawing which shows operation | movement when all the boarding doors and a back gate are closed. It is explanatory drawing which shows operation | movement when the back gate is open. It is explanatory drawing which shows operation | movement when the door for boarding / exiting is open. It is explanatory drawing which shows the relationship between the wave number of a standing wave, the arrangement | positioning of an antenna, and the phase of the transmission signal supplied to an antenna. It is explanatory drawing about each modification which deform | transformed the structure of the antenna part in 1st Embodiment. (A) is explanatory drawing which shows the structure and arrangement | positioning of the antenna part in the radio | wireless communications system of 2nd Embodiment, (b) is explanatory drawing which shows the modification. It is explanatory drawing about each modification which deform | transformed the structure of the antenna part in 2nd Embodiment.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
[First Embodiment]
<Overall configuration>
The wireless communication system of the present embodiment is mounted on a vehicle, and as shown in FIG. 1, a communication device 1 that transmits various commands by wireless communication, and an electronic device 3 that realizes a predetermined function according to the commands received by wireless communication. With. The vehicle includes doors for getting on and off on both the left and right sides, and a rear gate for opening and closing the trunk room at the rear. In the drawing, the part surrounded by a dotted line is a specific space SP in which all directions along the horizontal plane are surrounded by a metal body, and includes a part located below the window in the trunk room and the passenger compartment.

The electronic device 3 is a well-known device having a function of performing wireless communication and a function of realizing predetermined assigned processing, and is installed in a trunk room.
The communication device 1 includes an antenna unit 10 and a communication device main body 20, and the communication device main body 20 is installed below the driver seat. The antenna unit 10 includes four antennas 10F, 10R, 10D, and 10P. In the specific space SP, the antenna 10F is the front end of the vehicle, the antenna 10R is the rear end of the vehicle, and the antenna 10D is the right side of the vehicle ( The driver seat side end and the antenna 10P are arranged on the left side (passenger seat side) end of the vehicle. However, the antennas 10F and 10R and the antennas 10R and 10L are arranged at positions facing each other, and any of the antennas 10F, 10R, 10D, and 10P is specified along the metal body that is the boundary of the specific space SP. It is arranged near the lower end of the space SP.

  The arrangement of the electronic device 3 and the communication apparatus main body 20 is not limited to this, and the electronic device 3 may be arranged anywhere as long as it is in the specific space SP, and a plurality of electronic devices 3 may exist. Further, the communication device main body 20 may be arranged outside the specific space SP without being limited to the specific space SP. The arrangement of the antennas 10F, 10R, 10D, and 10P may not necessarily be near the lower end of the specific space SP as long as it follows the metal body.

  The antenna 10F has a radio wave radiation direction at the rear of the vehicle, and the antenna 10R has a radio wave radiation direction at the front of the vehicle. That is, the antennas 10F and 10R are installed such that the direction along the opening surface of the specific space SP formed when the passenger door is opened is the radio wave radiation direction. The antenna 10D has a radio wave emission direction from the right to the left as viewed in the vehicle forward direction, and the antenna 10P has a radio wave emission direction from the left to the right as viewed in the vehicle forward direction. That is, the antennas 10D and 10P are installed such that the direction along the opening surface of the specific space SP formed when the rear gate is opened is the radio wave radiation direction.

<Communication device body>
As shown in FIG. 2, the communication device main body 20 includes a communication processing unit 21, an antenna selection unit 22, a phase switching unit 23, and a control unit 24. The communication processing unit 21 generates a command to the electronic device 3 based on an instruction input from an operation input unit (not shown) and input signals from various sensors indicating the state of the vehicle and the state around the vehicle, and based on the command A transmission signal to be supplied to the antenna unit 10 is generated.

  The antenna selection unit 22 includes switches 22F, 22R, 22D, and 22P provided in the feed lines that individually feed power to the antennas 10F, 10P, 10D, and 10P, and is individually turned on / off according to instructions from the control unit 24. Can be switched.

  The phase switching unit 23 includes phase switching units 23F, 23P, 23D, and 23R respectively provided in individual feed lines, similarly to the switches that configure the antenna selection unit 22, and in accordance with instructions from the control unit 24, The phase of the transmission signal can be individually switched between the normal phase and the reverse phase. However, when the phase switchers 23F, 23P, 23D, and 23R are all set to the positive phase or the reverse phase, the feed lines to the antennas are radio waves transmitted from the antennas 10F, 10P, 10D, and 10P. Are wired so that all of the phases are the same.

  The control unit 24 is based on the detection result from the door sensor group 5 provided in the vehicle in order to individually detect the open / closed state of the door and trunk hood (or rear gate) (hereinafter simply referred to as “open / closed state of the door etc.”). Then, an excitation mode switching process for appropriately switching the settings of the antenna selection unit 22 and the phase switching unit 23 is executed so that radio waves are radiated in any one of three excitation modes described later.

<Frequency setting>
Here, the setting of the frequency of the transmission signal (and thus the radio wave radiated from the antenna unit 10) will be described. Assuming that the natural resonance frequency of the standing wave formed in the specific space SP whose rectangular shape is rectangular and surrounded by the conductor is _flm , the natural resonance frequency _flm is expressed by the following equation (1). Is done. However, a is the dimension of the specific space SP in the longitudinal direction of the vehicle body, b is the dimension of the specific space SP in the lateral direction of the vehicle body, c is the speed of light, l is the wave number of a standing wave formed in the longitudinal direction of the vehicle body, and m is the lateral direction of the vehicle body. Is the wave number of the standing wave formed in The wave numbers l and m (both are integers) represent excitation modes.

Then, P, Q, R, and S are all integers of 2 or more, the longitudinal mode (l, m) = (P, 1), the transverse mode (l, m) = (1, Q), the longitudinal and transverse mode (l , M) = (R, S), P, Q, R, S such that the frequencies are as close as possible (preferably included in the frequency band of the applied communication system). Ask for.

For example, when a = 3.6 m and b = 1.6 m, if the frequency to be used is around 300 MHz, f _lm = 306 MHz, (l, m) when (l, m) = (7,1) ) = (2,3), f _lm = 293 MHz, and (l, m) = (1,3), f _lm = 284 MHz. FIG. 3 is an explanatory diagram schematically showing the distribution of standing waves in each excitation mode, where (a) is the longitudinal mode (l, m) = (7, 1), and (b) is the transverse mode (l, m) = (1, 3), (c) indicates the vertical / horizontal mode (1, m) = (2, 3). In this case, a frequency near the center of the three resonance frequencies (for example, 295 MHz) may be set as the frequency of the transmission signal.

  In FIG. 3, the magnetic field formed by the standing wave is represented by an ellipse. In the standing waves adjacent to each other, the direction of the magnetic field (rotation direction) is reversed, and accordingly, the direction of the electric field is reversed vertically (see FIG. 9). Hereinafter, in FIGS. 6 to 9, “forward” and “reverse” in the drawings represent the directions of these magnetic fields and electric fields.

<Excitation mode switching process>
Here, the contents of the excitation mode switching process executed by the control unit 24 will be described with reference to the flowchart shown in FIG. This process starts when the ACC power supply of the vehicle is turned on and stops when it is turned off.

When this process is started, the control unit 24 sets the excitation mode to the vertical / horizontal mode by switching the settings of the antenna selection unit 22 and the phase switching unit 23 (S110).
Next, the control unit 24 determines whether there is a change in the open / closed state of the door or the like based on the detection result from the door sensor group 5 (S120). However, in an initial state, it is determined that all doors are in a closed state, and a change from that state is determined. If there is no change in the open / close state of the door or the like (S120: NO), the process returns to S120 and waits until the open / close state changes.

  When there is a change in the open / closed state of the door or the like (S120: YES), the control unit 24 determines whether or not the rear gate is opened based on the detection result from the door sensor group 5 (S130), and the rear gate is opened. If not (S120: NO), it is determined whether any of the entry / exit doors is opened (S150).

  If it is determined that the rear gate is open (S130: YES), the control unit 24 sets the excitation mode to the transverse mode by switching the settings of the antenna selection unit 22 and the phase switching unit 23 (S140), and S120. Return to. If it is determined that one of the passenger doors is opened (S150: YES), the control unit 24 switches the setting of the antenna selection unit 22 and the phase switching unit 23 to set the excitation mode to the vertical mode. Then (S160), the process returns to S120. If it is determined that both the rear gate and the entry / exit door are closed (S150: NO), the process returns to S110. That is, the excitation mode is set to the vertical / horizontal mode.

Here, the details of the processing performed when setting the excitation mode executed in the previous S110, S140, and S160 will be described with reference to the flowchart shown in FIG.
First, the control unit 24 sets the on / off state of each switch constituting the antenna selection unit 22 according to the excitation mode to be set (S210).

  Specifically, in the case of the vertical / horizontal mode, all the switches 22F, 22R, 22D, and 22P are set to ON. In the horizontal mode, the switches 22F and 22R are set to OFF and the switches 22D and 22P are set to ON. In this case, the switches 22F and 22R are turned on and the switches 22D and 22P are turned off.

Next, the control part 24 sets each phase switch which comprises the phase switch part 23 according to the wave number specified from an excitation mode (S220).
Specifically, as shown in FIGS. 6 to 8, when the standing wave generated in each excitation mode is expressed in the normal phase and the reverse phase, the standing wave located closest to the antenna that radiates the radio wave is shown. Set according to the phase. 6 to 8, in order to make the drawings easy to see, the longitudinal mode (m, l) = (3, 3), the longitudinal mode (m, l) = (4, 1), and the transverse mode (m, l). ) = (1, 3).

  In the case of the vertical / horizontal mode shown in FIG. 6, all the phase switches 23F, 23R, 23D, 23P related to the operation are set to the positive phase, and in the case of the horizontal mode shown in FIG. 23D and 23P are both set to the normal phase, and in the case of the longitudinal mode shown in FIG. 8, the phase switch 23F related to the operation is set to the normal phase and the phase switch 23R is set to the reverse phase.

  That is, if the wave number m is an odd number, the phase switchers 23F and 23R are both set to be in positive phase or both in reverse phase, and if the wave number m is an even number, one is normal phase and the other is reverse phase. Set to phase. If the wave number l is an odd number, the phase switchers 23D and 23P are set so that both are in the positive phase or both in the reverse phase. If the wave number l is an even number, one is the positive phase and the other is the reverse phase. Set as follows. In the case of the vertical / horizontal mode, settings are made so as to satisfy the above-described relationship and satisfy the relationship described below. That is, for example, when the upper left standing wave in FIG. 6 is used as a base point, the standing wave located at the p-th (p = 2 in the drawing) in the left-right direction from the base point and the antennas 10F and 10R face each other. Assuming that the standing wave located at the q-th (q = 2 in the figure) and the antennas 10D and 10P face each other in the front-rear direction, the phase switches 23F and 23D have an odd number of (p + q-1) So that they are in phase with each other, and if (p + q-1) is an even number, they are set in phase with each other. As another specific example, as shown in FIG. 9, when the longitudinal and transverse modes (m, l) = (4, 2) and the positional relationship between the standing wave and the antenna is p = 1, q = 2, In order to improve the radiation efficiency of the antenna unit 10, the antennas 10F, 10R, 10D, and 10P are formed in the respective excitation modes. It is desirable to install it as close as possible to the position facing the part of the waves (position where the magnetic current is parallel to the antenna surface).

  Note that the control executed by the control unit 24 may be realized by hardware such as a logic circuit, or the control unit 24 is configured by a microcomputer, and the control is realized by processing executed by the microcomputer, that is, software. May be.

<Operation>
In the wireless communication system configured as described above, when all of the passenger doors and the back gate are closed, the excitation mode is the vertical and horizontal modes, and as shown in FIG. A wave is formed.

  When the back gate is open, the excitation mode is the transverse mode, and as shown in FIG. 7, the radiation of radio waves in the direction orthogonal to the standing wave formation direction (left-right direction) by the antennas 10D and 10P is generated. It is suppressed. As a result, leakage of radio waves from the opening surface of the specific space SP formed when the back gate is opened to the outside is suppressed.

  When the entrance door is in the open state, the excitation mode is the longitudinal mode, and as shown in FIG. 8, the radiation of the radio wave in the direction orthogonal to the direction (longitudinal direction) in which the standing waves are formed by the antennas 10F and 10R. Is suppressed. As a result, leakage of radio waves from the opening surface of the specific space formed when the passenger door is opened to the outside is suppressed.

<Effect>
As described above, in the present embodiment, when the passenger door or the back gate is opened, the excitation mode is set to the vertical mode or the excitation mode according to the position of the opening surface of the specific space SP formed by the opened doors. By switching to the transverse mode, leakage of radio waves from the aperture surface is suppressed. For this reason, communication can be continued even when the door for getting on and off and the back gate are opened.

  In addition, when both the passenger door and the back gate are closed, standing waves distributed in the vehicle front-rear left-right direction are formed in the specific space SP by switching the excitation mode to the vertical and horizontal modes. Compared with the case of operating in the vertical mode or the horizontal mode, the electric field strength in the passenger compartment can be kept more uniform and high.

<Modification>
In the present embodiment, a total of four antennas are provided at each of the front end, rear end, right end, and left end of the vehicle in the passenger compartment. However, as shown in FIG. 10A, antennas 10D and 10P are provided. One of them (antenna 10P in the figure) may be omitted, or as shown in FIG. 10B, one of antennas 10F and 10R (antenna 10R in the figure) may be omitted. Further, as shown in FIG. 10C, either one of the antennas 10D and 10P and one of the antennas 10F and 10R (antennas 10P and 10R in the figure) may be omitted. In these cases, a switch and a phase switch corresponding to the omitted antenna can be omitted, and the apparatus configuration can be simplified.

[Second Embodiment]
In the first embodiment, the antenna unit 10 is composed of four antennas, and the excitation mode is switched according to the opening / closing of the door. On the other hand, in the present embodiment, as shown in FIG. 11A, the antenna unit 10 is configured by only the antennas 10F and 10R, and only the operation corresponding to the vertical mode is performed.

  According to the present embodiment, since leakage of radio waves from the opening surface of the specific space SP formed when the passenger door is opened, communication can be continued even when the passenger door is opened. Moreover, since it is not necessary to switch the excitation mode according to the open / closed state of the door, the apparatus configuration can be simplified.

<Modification>
In the present embodiment, as shown in FIG. 11B, one of the antennas 10F and 10R (the antenna 10R in the figure) constituting the antenna unit 10 may be omitted. In this case, since the phase adjustment between the antennas is unnecessary, the apparatus configuration can be further simplified.

  In the second embodiment, the antenna unit 10 includes only the antennas 10F and 10R. However, as illustrated in FIG. 12A, the antenna unit 10 includes only the antennas 10D and 10P, which corresponds to the transverse mode. Only the operation may be performed. Furthermore, as shown in FIG. 12B, either one of the antennas 10D and 10P (the antenna 10P in the figure) constituting the antenna unit 10 may be omitted. In these cases, since leakage of radio waves from the opening surface of the specific space SP formed when the rear gate is opened is suppressed, communication can be continued even when the rear gate is opened. In particular, in the latter case, it is not necessary to adjust the phase between the antennas, so that the apparatus configuration can be further simplified.

[Other Embodiments]
As mentioned above, although embodiment of this invention was described, it cannot be overemphasized that this invention can take a various form, without being limited to the said embodiment.

  (1) In the above embodiment, the case where the wireless communication system is mounted on a vehicle has been described. However, the present invention is not limited to this, and a specific space that is covered with a conductor and may be opened to an external space by an opening / closing member. You may apply to various mobile bodies, buildings, etc. which need to communicate within.

  (2) Each component of the present invention is conceptual and is not limited to the above embodiment. For example, the functions of one component may be distributed to a plurality of components, or the functions of a plurality of components may be integrated into one component. Further, at least a part of the configuration of the above embodiment may be replaced with a known configuration having the same function. In addition, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Communication apparatus 3 ... Electronic device 5 ... Door sensor group 10 ... Antenna part 20 ... Communication apparatus main body 21 ... Communication processing part 22 ... Antenna selection part 23 ... Phase switching part 24 ... Control part SP ... Specific space

Claims (5)

The horizontal direction with the boundary surface of the specific space opened to the external space by an opening / closing member that opens and closes the specific space is installed in a specific space (SP) covered at least in the horizontal direction with a conductor. And the antenna part 10 which consists of one or more antennas which radiate | emits a radio wave in the direction along the said open surface,
A communication device (20) for transmitting radio waves using the antenna unit;
The radio communication system is characterized in that the frequency of the radio wave radiated from the antenna unit is set to a size such that a standing wave is formed in the specific space along the radiation direction of the radio wave. . The opening / closing member is provided at a plurality of locations such that the directions of the open surfaces are different from each other,
The antenna unit includes a plurality of antennas corresponding to the orientations of the open surface,
The communication device
Monitoring means (24: S120, S130, S150) for individually monitoring the open / closed state of the open / close member;
Switching means (22, 24) for switching the antenna to be used so that the antenna associated with the target surface is selected with the open surface of the opening / closing member detected as being in the open state by the monitoring means. S210),
The wireless communication system according to claim 1, further comprising: The antenna unit includes a pair of antennas opposed to each other and associated with the same open surface,
The communication device adjusts a phase of a transmission signal supplied to the pair of antennas to be in phase or in phase by a wave number of a standing wave formed by radio waves radiated from the pair of antennas. The wireless communication system according to claim 1, further comprising (23, S24: S220).   The wireless communication system according to any one of claims 1 to 3, wherein the specific space is a vehicle cabin space.   The wireless communication system according to any one of claims 1 to 4, wherein the opening / closing member includes at least one of a door and a rear gate of the vehicle.