JP2003060543A - In-vehicle radio communication apparatus and system thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve in-vehicle radio communication between a fixed station and a mobile station in vehicles. SOLUTION: In order to perform radio communication mutually with a mobile terminal in a vehicle, an In-vehicle radio communication apparatus is installed in the vehicle. A dipole antenna 11 is arranged in a vertical direction at the dashboard of the vehicle. A dipole antenna 12 is arranged in a horizontal direction. The main polarization of the dipole antenna 11 becomes vertical polarization, and the main polarization of the dipole antenna 12 becomes horizontal polarization. The comparing and selecting device 13 of a diversity device 15 compares the reception levels of the dipole antennas 11 and 12 and selects one of them of a higher reception level. A transmitter and receiver 14 communicates with the mobile station by using the selected antenna. Whichever direction the polarization direction of the mobile station may be, in-vehicle radio communication is improved by polarization diversity reception.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-vehicle wireless communication device, and more particularly to an in-vehicle wireless communication device installed in a vehicle so as to mutually wirelessly communicate with a mobile terminal in the vehicle.

[0002]

2. Description of the Related Art A conventional wireless communication system in a vehicle is, for example, "Nikkei Electronics (1999.12.
13) No. 759 ”, pages 142-143. This is because fixed stations such as audio devices and navigation devices installed in automobiles and mobile stations such as mobile phones, headsets and notebook personal computers brought into automobiles are equipped with antennas and Bluetooth modules, respectively. Then, an in-vehicle wireless system that enables communication between the devices is configured.

[0003]

However, the conventional in-vehicle wireless communication system has a problem that the in-vehicle wireless communication cannot be satisfactorily performed. Because the polarization of the fixed station is determined by the type of antenna and its installation direction, but the direction of the polarization of the mobile station brought into the vehicle is not determined, so the polarization of the fixed station is vertical polarization, This is because if the polarized wave of the mobile station is horizontal polarized wave, good communication cannot be performed.

Further, in the vehicle, since a reflected wave is generated at the door or roof, the fading environment has a high polarization dependency, and there is a problem that the reception level drops significantly depending on the position of the mobile station. It was

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems and provide an in-vehicle wireless communication device capable of favorably performing in-vehicle wireless communication between a fixed station and a mobile station in the vehicle. .

[0006]

In order to solve the above problems, the present invention provides an in-vehicle wireless communication device installed at a predetermined place in a vehicle so as to perform wireless communication with a mobile terminal in the vehicle. A plurality of antennas arranged so that polarization directions are different from each other and diversity means for selecting or combining reception signals of the plurality of antennas are provided. With this configuration, the in-vehicle wireless communication between the fixed station and the mobile station can be favorably performed by the polarization diversity reception.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. For simplicity,
In all the embodiments, description will be made assuming that Bluetooth is an example of the in-vehicle wireless communication means and the used frequency is the 2.4 GHz band.

(First Embodiment) A first embodiment of the present invention is an in-vehicle wireless communication device in which two antennas having different polarization directions are arranged on a dashboard of a vehicle.

FIG. 1 is a conceptual diagram showing a basic configuration of an in-vehicle wireless communication device according to the first embodiment of the present invention.
FIG. 1A is a block diagram of an in-vehicle wireless communication device. FIG. 1B is a front view of the in-vehicle wireless communication device built in the dashboard of the automobile as seen from the inside of the vehicle.
In FIG. 1, dipole antennas 11 and 12 are antennas arranged in a vertical direction and a horizontal direction. Comparison selection device
13 is a means for comparing the reception levels of the dipole antennas 11 and 12 and selecting a dipole antenna having a high reception level. The transmission / reception device 14 is a device that wirelessly communicates with a mobile station in the vehicle. The diversity device 15 is means for selecting one of the received signals of the two antennas, whichever has the higher received level. A means for synthesizing the reception signals of the two antennas and averaging the reception sensitivity may be used.

FIG. 2 is a diagram showing the reception level when the position of the mobile station is changed in the automobile. In FIG. 2, the horizontal axis represents the relative position inside the vehicle, and the vertical axis represents the reception level. FIG. 2A is a diagram showing the reception levels in the transmission / reception device 14 when the comparison / selection device 13 always selects the dipole antenna 11 and when the dipole antenna 12 is always selected. A solid line 21 indicates the reception level of vertically polarized waves by the dipole antenna 11. solid line
Reference numeral 22 indicates the level of horizontally polarized wave received by the dipole antenna 12.

FIG. 2B is a diagram showing the reception level in the transmission / reception device 14 when the comparison / selection device 13 appropriately switches the dipole antennas 11 and 12 to perform polarization diversity reception. The solid line 23 is the envelope above the solid lines 21 and 22. The minimum amount of change in the position of the mobile station is sufficiently smaller than 1/20 of one wavelength (about 120 mm).

FIG. 3 is a diagram showing a cumulative probability distribution derived from each reception level shown in FIG. 2, with the horizontal axis representing the reception level,
The vertical axis represents the cumulative probability distribution of the reception level. The horizontal axis represents the median value of the reception level normalized to 0 dB. The solid line 31 corresponds to the vertical polarization of the solid line 21, the solid line 32 corresponds to the horizontal polarization of the solid line 22, and the solid line 33 corresponds to the polarization diversity of the solid line 23. The dotted line 34 indicates the Rayleigh distribution. As can be seen from the figure, the polarization diversity has a higher probability of increasing the reception level.

The operation of the in-vehicle wireless communication device according to the first embodiment of the present invention configured as described above will be described. First, the function of each unit of the in-vehicle wireless communication device will be described with reference to FIG. Dipole antenna 11,12
Is composed of, for example, a conductor plate having a width of about 1 mm. Its length is about half the wavelength of the operating frequency (operating frequency is 2.
In case of 4 GHz, it is set to 60 mm). The dipole antenna 11 is arranged in the vertical direction (indicated by Z in the figure) in the automobile. The dipole antenna 12 is arranged orthogonal to the dipole antenna 11 in the horizontal direction (indicated by Y in the drawing).

The feed points of the dipole antennas 11 and 12 are connected to the comparison / selection device 13 and the transmission / reception device 14 of the diversity device 15. The ground points of the dipole antennas 11 and 12 are connected to a chassis of an automobile (not shown) or the like. Therefore, the main polarization of the dipole antenna 11 becomes vertical polarization, and the main polarization of the dipole antenna 12 becomes horizontal polarization. The comparison / selection device 13 compares the reception levels from the dipole antenna 11 and the dipole antenna 12, and selects the dipole antenna having a high reception level.

Next, with reference to FIGS. 2 and 3, the radio wave propagation characteristics in the vehicle when the in-vehicle wireless communication device of the present embodiment is used will be described. As is clear from Figs. 2 and 3, vertically polarized waves (21, 31) are horizontally polarized waves (22, 32).
The fading is shallower than that. Polarization diversity (23, 3
In 3), fading is even shallower than vertical polarization. 0.1
With a cumulative probability of%, the diversity gain due to polarization diversity is about 13 dB higher than vertically polarized waves. Therefore, in-vehicle wireless communication can be satisfactorily performed regardless of the direction of polarization of a mobile station such as a mobile phone, a headset, or a notebook personal computer brought into an automobile.

Although the dipole antenna has been described as an example, the type of the antenna is not limited to this, and a patch antenna, a loop antenna, a monopole antenna, a slot antenna or the like may be used. The location for fixing the antenna is not limited to the dashboard, but may be a rearview mirror, a roof, a center console, or the like. The number of antennas may be three or more. In any case, if the antenna is arranged in the vehicle so that the polarization directions are different, almost the same effect can be obtained.

As described above, in the first embodiment of the present invention, since the in-vehicle wireless communication device has two antennas with different polarization directions arranged on the dashboard, it is fixed by polarization diversity reception. In-vehicle wireless communication between the station and the mobile station can be favorably performed.

(Second Embodiment) A second embodiment of the present invention is an in-vehicle wireless communication device in which two antennas are arranged on a dashboard of a vehicle at a distance.

FIG. 4 is a front view of the in-vehicle wireless communication device according to the second embodiment of the present invention. It is the figure which looked at the in-vehicle wireless communication device built into the dashboard of the automobile from the interior of the vehicle. The functional block diagram of the in-vehicle wireless communication device is
Since it is the same as FIG. In FIG.
The dipole antenna 11 is at a certain point in the car (position 1)
The antenna is located at. Dipole antenna 12
Is an antenna placed at another point (position 2) with a distance from the dipole antenna 11. Dipole antenna
The power supply points 11 and 12 are comparison / selection devices for the diversity device 15.
13 and the transmitter / receiver 14. The ground points of the dipole antennas 11 and 12 are connected to a car chassis (not shown) or the like. The same components are designated by the same reference numerals, and detailed description will be omitted.

FIG. 5 is a diagram showing the reception level of the in-vehicle wireless communication device according to the second embodiment of the present invention. It is a figure which shows the case where the position of a mobile station is changed in a vehicle. FIG. 5A is a diagram showing the reception levels in the transmission / reception device 14 when the comparison / selection device 13 always selects the dipole antenna 11 and when the dipole antenna 12 is always selected. A solid line 51 indicates the reception level of the dipole antenna 11 at the position 1. The solid line 52 shows the reception level by the dipole antenna 12 at the position 2. Figure 5 (b)
FIG. 6 is a diagram showing a reception level in the transmission / reception device 14 when the comparison / selection device 13 appropriately switches the dipole antennas 11 and 12 to perform space diversity reception. The solid line 53 is
It is the envelope above the solid lines 51 and 52. The minimum amount of change in the position of the mobile station is sufficiently smaller than 1/20 of one wavelength (about 120 mm).

FIG. 6 is a diagram showing a cumulative probability distribution derived from each reception level shown in FIG. 5, in which the median value is normalized to 0 dB. The solid line 61 corresponds to the solid line 51 indicating the reception level of the dipole antenna 11 at the position 1. The solid line 62 corresponds to the solid line 52 indicating the reception level of the dipole antenna 12 at the position 2. The solid line 63 corresponds to the space diversity of the solid line 53. The dotted line 64 indicates the Rayleigh distribution.

The operation of the in-vehicle wireless communication device according to the second embodiment of the present invention configured as described above will be described. The basic operation of the in-vehicle wireless communication device shown in FIG.
Since this is the same as the first embodiment, only the different points will be described. The comparison / selection device 13 compares the reception level of the dipole antenna 11 arranged at the position 1 with the reception level of the dipole antenna 12 arranged at the position 2,
Select a dipole antenna with a high reception level.

The radio wave propagation characteristics in the automobile will be described with reference to FIGS. 5 and 6. As is apparent from FIGS. 5 and 6, the reception level (52, 62) at position 2 is at position 1
Fading is shallower than the reception level (51, 61). At the reception level (53, 63) using space diversity,
Fading is shallower than the reception level at position 2. 0.
At a cumulative probability of 1%, the diversity gain due to spatial diversity is about 10 dB higher than at position 2. Therefore, in-vehicle wireless communication can be favorably performed even if the position of a mobile station such as a mobile phone, a headset, or a notebook personal computer brought into an automobile changes.

The type of antenna has been described by taking a dipole antenna as an example, but the present invention is not limited to this and may be a patch antenna, a loop antenna, a monopole antenna, a slot antenna, or the like. The location for fixing the antenna is not limited to the dashboard, but may be a rearview mirror, a roof, a center console, or the like. The number of antennas may be three or more. In any case, if the antennas are arranged in the vehicle at a distance, almost the same effect can be obtained.

As described above, according to the second embodiment of the present invention, since the in-vehicle wireless communication device has the structure in which the two antennas are arranged on the dashboard at a distance, the space diversity reception can be performed. In-vehicle wireless communication between the fixed station and the mobile station can be favorably performed.

(Third Embodiment) A third embodiment of the present invention is an in-vehicle wireless communication device in which two antennas having different directivities are arranged in a center console.

FIG. 7 is a diagram showing a basic configuration of an in-vehicle wireless communication device according to the third embodiment of the present invention. Figure 7
(A) is a functional block diagram of an in-vehicle wireless communication device. FIG. 7B is a top view of the in-vehicle wireless communication device built in the center console of the automobile as viewed from above the automobile. FIG. 7C is a side view of the automobile as viewed from the lateral direction. In FIG. 7, the antenna 71 is a half-wavelength dipole antenna. The antenna 72 is an open-ended diamond antenna. The center console 74 is a console box provided between the driver seat and the passenger seat.

FIG. 8 is a diagram showing the details of the in-vehicle wireless communication device built in the center console of the automobile. Figure 8
(A) is a perspective view. FIG. 8B is a top view seen from above. FIG. 8C is a side view seen from the lateral direction. FIG. 8D is a rear view seen from the rear side. The same components as those in the first and second embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 9 is a diagram showing a radiation pattern on the vertical XZ plane of the dipole antenna 71 and the open-ended diamond antenna 72 with a reflector. FIG. 10 is a diagram showing the reception level when the position of the mobile station is changed in the automobile. Figure 10
(A) shows the case where the comparison / selection device 13 always selects the dipole antenna 71, and the open-ended diamond antenna 72 with a reflector.
FIG. 6 is a diagram showing a reception level in the transmission / reception device 14 when is always selected. FIG. 11 is a diagram showing a cumulative probability distribution derived from each reception level shown in FIG.

The operation of the in-vehicle wireless communication device according to the third embodiment of the present invention configured as described above will be described. First, the antenna will be described. The antenna 71 shown in FIGS. 7 and 8 is composed of, for example, a linear conductor having a diameter of about 1 mm. The length of the antenna element is about half the wavelength of the operating frequency (60 mm). It is composed of antenna elements 71-1 and 71-2 each having a length of about a quarter wavelength. The antenna 71 is arranged in the vertical direction on the rear side of the center console 74.

One antenna element 711 of the antenna 71 is
The comparison / selection device 13 of the diversity device 15 and the transmission / reception device 14 are also connected via a feeding point 75 provided at one end thereof. The other antenna element 712 of the antenna 71 is connected to the conductor plate 73 via a ground point 76 provided at one end thereof. The other ends of the antenna elements 711 and 712 are electrically open. The antenna elements 711 and 712 form a dipole antenna 71.

On the other hand, each of the antenna elements 721 and 722 has a length of about 1 wavelength (120 mm). It is composed of a conductor plate having a width of 1 mm. The antenna elements 721 and 722 are bent at an angle of 90 degrees at a position of half the length and face each other so as to form a rhombus, and are horizontally arranged on the upper surface of the center console 74. The conductor plates 73 are arranged inside the center console 74 in parallel with the diamond-shaped antenna 72 and separated by a distance d (for example, 30 mm). The length of one side of the conductor plate 73 is one wavelength (120 mm) or more.

One antenna element 721 of the antenna element 72
Is connected to the comparison / selection device 13 of the diversity device 15 and the transmission / reception device 14 via a feeding point 77 provided at one end thereof. The other antenna element 722 of the antenna 72 is connected to the conductor plate 73 via a ground point 78 provided at one end thereof. The other ends of the antenna elements 721 and 722 are electrically open. The antenna elements 721 and 722 form a diamond-shaped open-ended antenna. Since the conductor plate 73 operates as a reflector because one side has one wavelength or more, an open-ended diamond antenna with a reflector is formed.

Next, the diversity operation will be described. FIG. 9 shows the radiation patterns of the dipole antennas 711 and 712 and the open-ended diamond-shaped antennas 721 and 722 with a reflector in the vertical (XZ) plane. A solid line 91 shows the vertically polarized component of the dipole antenna 71. The directional gain in the horizontal (XY) plane is
It is about 0 dBd. On the other hand, the dotted line 92 shows the horizontally polarized component of the open-ended diamond antenna 72 with a reflector. Roof (Z)
It becomes unidirectional in the direction, and the directional gain is about 8 dBd. Therefore, the dipole antenna 71 is suitable for communication with a mobile station located in the horizontal direction, while the open-ended diamond antenna 72 with a reflector is suitable for communication using reflected waves from the roof. The comparison / selection device 13 compares the reception levels of the dipole antenna 71 and the open-ended diamond-shaped antenna 72 with a reflector, and selects the antenna with the higher reception level.

Thirdly, with reference to FIGS. 10 and 11, the radio wave propagation characteristic in the vehicle when the in-vehicle wireless communication device of the present embodiment is used will be described. FIG. 10 shows the reception level when the position of the mobile station is changed in the car. FIG. 10A shows the reception level in the transmission / reception device 14. A solid line 101 represents a horizontal plane directivity reception level by the dipole antenna 71, and is a case where the comparison / selection device 13 always selects the dipole antenna 71. The solid line 102 is
This is the reception level of the directivity in the Z direction by the open-ended diamond-shaped antenna 72 with a reflector, and is the case where the comparison and selection device 13 always selects the open-ended diamond-shaped antenna 72 with a reflector.

FIG. 10 (b) shows the reception level in the transmission / reception device 14 when the comparison / selection device 13 appropriately switches the dipole antenna 71 and the open-ended diamond-shaped antenna 72 with a reflector to receive the directional diversity. Solid line 103 is solid line 1
It is the upper envelope of 01 and 102. The minimum amount of change in the position of the mobile station is measured sufficiently smaller than 1/20 of one wavelength (about 120 mm).

FIG. 11 shows a cumulative probability distribution derived from each reception level shown in FIG. Median reception level is 0 dB
Is normalized to. The solid line 111 corresponds to the horizontal plane directivity of the solid line 101, the solid line 112 corresponds to the Z-direction directivity of the solid line 102, and the solid line 113 corresponds to the directivity diversity of the solid line 103. The dotted line 114 indicates the Rayleigh distribution.

10 and 11, horizontal plane directivity (10
The fading of (1, 111) is shallower than that of the Z direction directivity (102, 112). With directional diversity (103, 113), fading is even shallower than horizontal directionality. 0.1
With the cumulative probability of%, the diversity gain due to the directional diversity is as high as about 12 dB. Therefore, in-vehicle wireless communication can be favorably performed regardless of the position or directivity of a mobile station such as a mobile phone, a headset, or a notebook personal computer brought into the vehicle.

The type of antenna is not limited to that of this embodiment, but may be a patch antenna, a loop antenna, a monopole antenna, a slot antenna, or the like. The location for fixing the antenna is not limited to the center console, and may be a dashboard, a rearview mirror, a roof, or the like.
The number of antennas may be three or more. In any case, if the antennas are arranged in the vehicle so that the maximum radiation directions are different, almost the same effect can be obtained.

As described above, in the third embodiment of the present invention, the in-vehicle wireless communication device is installed in the center console,
Since two antennas having different directivities are arranged, directional diversity reception can be performed, and in-vehicle wireless communication between the fixed station and the mobile station can be favorably performed.

(Fourth Embodiment) In a fourth embodiment of the present invention, an antenna is integrated with a front panel of an information communication terminal device, and two antennas having different polarization directions are arranged in a vehicle. It is a wireless communication device.

FIG. 12 is a diagram showing the basic configuration of an in-vehicle wireless communication device according to the fourth embodiment of the present invention. Figure 12
(A) is a front view of a state in which an antenna of an in-vehicle wireless communication device is built in a front panel of an information communication terminal device such as a car navigation device or an audio device. Figure 12
(B) is the side view which looked at this from the side. Figure 12 (c)
[FIG. 1] is a front view of a car navigation device built in a dashboard of an automobile as seen from the inside of a vehicle. A block diagram of the in-vehicle wireless communication device is the same as that in FIG. In FIG. 12, the conductor plate 121 is a ground conductor. The display screen unit 122 is a display unit on the front panel of the car navigation device. The front panel 123 is a front panel of the car navigation device. The same components are designated by the same reference numerals, and detailed description will be omitted.

The operation of the in-vehicle wireless communication device according to the fourth embodiment of the present invention configured as described above will be described. First, the antenna will be described. The dipole antenna 11 is a front panel of the car navigation system.
It is vertically installed on one side of the outer circumference of the 16 display screens 122. The dipole antenna 12 is the other one on the outer periphery of the display screen section 122 of the front panel 123 of the car navigation device.
It is built in at the side of the dipole antenna 11 orthogonal to it. The dipole antennas 11 and 12 are connected to the comparison / selection device 13 of the diversity device 15 and the transmission / reception device 14 via a feeding point provided at one end of each central gap. A ground point is provided at the other end of the gap at the center of each of the dipole antennas 11 and 12,
It is grounded to the conductor plate 121. Therefore, the main polarization of the dipole antenna 11 becomes vertical polarization, and the main polarization of the dipole antenna 12 becomes horizontal polarization.

Secondly, the diversity operation will be described. The comparison / selection device 13 compares the reception levels of the dipole antenna 11 and the dipole antenna 12, and selects the dipole antenna with the higher reception level. The dipole antennas 11 and 12 and the diversity device 15 can be integrated with the front panel 123 of the car navigation device. The car navigation device integrated with the front panel 123 can be installed in the front of the vehicle interior such as an in-dash or a dashboard. The radio wave propagation characteristics in the vehicle when the in-vehicle wireless communication device of the present embodiment is used are similar to the characteristics shown in FIGS. 2 and 3. Diversity gain by polarization diversity is about 10
Since the dB is improved, the in-vehicle wireless communication can be satisfactorily performed regardless of the polarization direction of the mobile station.

The type of antenna integrated with the front panel is not limited to that of this embodiment, but may be a patch antenna, a loop antenna, a monopole antenna, a slot antenna, or the like. The number of antennas may be three or more. In any case, if the front panel is built so that the polarization directions are different, almost the same effect can be obtained.

The device incorporating the antenna is not limited to the car navigation device, and the same effect can be obtained as long as it is a device fixed in the vehicle, such as an audio device. The position where the antenna is built in is not limited to the position of this embodiment,
Space diversity may be achieved by incorporating one antenna on each of the outer peripheries of the front panel facing each other. The same effect can be obtained even if two antennas having different directivities are built in to achieve directivity diversity.

As described above, in the fourth embodiment of the present invention, the in-vehicle wireless communication device has the antenna integrated with the front panel of the information communication terminal device, and two antennas having different polarization directions are arranged. With this configuration, the fixed station can be downsized and simplified, and polarization diversity reception can favorably perform in-vehicle wireless communication between the fixed station and the mobile station.

(Fifth Embodiment) In a fifth embodiment of the present invention, an antenna is integrated with a front panel of a car navigation to perform polarization diversity reception by switching polarization with one antenna. It is an in-vehicle wireless communication device.

FIG. 13 is a diagram showing a basic configuration of an in-vehicle wireless communication device according to the fifth embodiment of the present invention. FIG. 3 is a front view of a state in which the antenna of the in-vehicle wireless communication device is built in the front panel of the car navigation device. Figure 13
, The loop antenna 131 has a length of one wavelength (about 60
mm) loop antenna. The length of one side is a quarter wavelength (about 15 mm).

The operation of the in-vehicle wireless communication device according to the fifth embodiment of the present invention configured as described above will be described. The one-wavelength loop antenna 131 is built in on the outer periphery of the display screen section 136 of the front panel 137 of the car navigation device. A gap is provided at the center of each of the two orthogonal sides, and a selection device 132 and a selection device 133 are provided in each gap. The selection devices 132 and 133 are
It is connected to the comparison / selection device 134 and the transmission / reception device 135.
The selection device 132, the selection device 133, and the comparison selection device 134 operate in conjunction with each other, and transit between the two states.

This operation will be described with reference to FIGS. 13 (a) and 13 (b). FIG. 13A shows a first state of the selection devices 132 and 133 and the comparison selection device 134. FIG. 13B shows the second state of the selection devices 132 and 133 and the comparison selection device 134. As shown in FIG. 13A, when the selection device 133 closes the one-wavelength loop antenna, the selection device 132 is connected to the comparison / selection device 134 and the transmission / reception device 135. The main polarization at this time is vertical polarization.

On the other hand, as shown in FIG.
If 132 closes the one wavelength loop antenna, the selection device 133 is connected to the comparison selection device 134 and the transceiver device 135. The main polarization at this time becomes horizontal polarization. Comparison selection device
Reference numeral 134 compares the reception levels of the vertically polarized wave shown in FIG. 13A and the horizontally polarized wave shown in FIG. 13B and selects the dipole antenna with the higher reception level. In this way, one antenna can switch between vertically polarized waves and horizontally polarized waves. The directional gain can be increased as compared with the case where two antennas are used as in the first to fourth embodiments.

The radio wave propagation characteristics in the automobile when the in-vehicle wireless communication device of the present embodiment is used are similar to the characteristics shown in FIGS. Since the diversity gain due to the polarization diversity is improved by about 10 dB, the in-vehicle wireless communication can be favorably performed regardless of the polarization direction of the mobile station.

In this way, the in-vehicle wireless communication device is
It can be integrated with the front panel 137 of the car navigation device. The car navigation device, which is integrated with the front panel 137, can be installed on the in-dash in front of the vehicle compartment or on the dashboard. The type of antenna that is integrated with the front panel is
The present invention is not limited to this embodiment, and may be a circular one-wavelength loop antenna or an elliptical one-wavelength loop antenna. Similar effects can be obtained as long as the polarization changes by switching the feeding point in one antenna. The device incorporating the antenna is not limited to the car navigation device, and the same effect can be obtained as long as it is a device fixed in the vehicle, such as an audio device.

As described above, in the fifth embodiment of the present invention, the in-vehicle wireless communication device has the antenna integrated with the front panel of the car navigation, and the polarization diversity is achieved by switching the polarization with one antenna. Since the device is configured to perform reception, the device can be downsized and simplified, and the in-vehicle wireless communication between the fixed station and the mobile station can be favorably performed.

(Sixth Embodiment) A sixth embodiment of the present invention is an in-vehicle wireless communication device in which an antenna is built in a front panel of a car navigation system and a rear of a headrest.

FIG. 14 is a diagram showing the basic structure of an in-vehicle wireless communication device according to the sixth embodiment of the present invention. Figure 14
(A) is a functional block diagram of an in-vehicle wireless communication device. FIG. 14B shows an antenna of the in-vehicle wireless communication device,
It is a top view of the state where it was built into the front panel and the back of the headrest of the car navigation device. Figure 14 (c)
Is a side view thereof. In FIG. 14, the antenna 141
Is an antenna built in the front panel of the car navigation system. The antenna 142 is an antenna built in the rear of the headrest. The same components as those in the first to fifth embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

The operation of the in-vehicle wireless communication device according to the sixth embodiment of the present invention configured as above will be described. The arrows in FIG. 14 indicate the state of radio waves radiated from the antennas 141 and 142. The antenna 141 radiates radio waves toward the center of the passenger compartment, and the antenna 142 radiates radio waves toward the center of the rear seat. The two antennas are arranged in the vehicle so as to be spaced apart from each other and have different maximum radiation directions. Even if the radio wave of the antenna 141 is blocked by the human body or a sheet, the radio wave of the antenna 142 can be received. In this way, radio waves can reach every corner of the vehicle.

The type of antenna used is not limited, and a dipole antenna, a patch antenna, a loop antenna, a monopole antenna, a slot antenna or the like may be used. The antenna may be fixed not only in the car navigation device and headrest but also in the dashboard, room mirror, roof, room lamp and rear tray. The number of antennas may be three or more. In any case, substantially the same effect can be obtained by arranging the antennas so that the maximum radiation direction is different from each other in the vehicle so that radio waves are not blocked by the human body or the seat.

As described above, in the sixth embodiment of the present invention, the antenna of the in-vehicle wireless communication device is built in the front panel and the rear of the headrest of the car navigation device. Thus, even if the radio wave from one antenna is blocked, the other antenna can receive the radio wave, and the in-vehicle wireless communication between the fixed station and the mobile station can be favorably performed.

(Seventh Embodiment) A seventh embodiment of the present invention is an in-vehicle wireless communication device equipped with three antennas whose polarization planes are orthogonal to each other in the vehicle interior.

FIG. 15 is a diagram showing the basic structure of an in-vehicle wireless communication device according to the seventh embodiment of the present invention. Figure 15
(A) is a functional block diagram of an in-vehicle wireless communication device. FIG. 15B is a top view showing a state where the three antennas are built in the dashboard and the roof. Figure 15 (c)
Is a side view thereof. In FIG. 15, the dipole antenna 151 is an antenna horizontally arranged on the ceiling of the vehicle compartment. The same components as those of the first to sixth embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

The operation of the in-vehicle wireless communication device according to the seventh embodiment of the present invention configured as above will be described. The dipole antennas 11 and 12 are built in the dashboard or the front panel of the car navigation system, similar to those shown in FIGS. 1 and 12. The dipole antenna 11 is arranged in the vertical (Z) direction, and the dipole antenna 12 is arranged in the horizontal (Y) direction. The dipole antenna 151 is built in the roof or the room lamp and is arranged in the horizontal (X) direction. That is,
The three antennas are arranged in the vehicle so that the polarization directions of the three antennas are spatially orthogonal to each other.

The comparison / selection device 152 compares the reception levels from the three dipole antennas and selects the dipole antenna having the highest reception level. A case where a mobile station (not shown) has a dipole antenna will be described as an example. When the axis of the mobile station dipole antenna is in the X direction,
The reception level at the dipole antenna 151 is the highest. When the axis of the mobile station dipole antenna is in the Y direction, the reception level at the dipole antenna 12 is the highest. When the axis of the mobile station dipole antenna is in the Z direction, the reception level at the dipole antenna 11 is the highest.

The type of antenna used is not limited to that of this embodiment. It may be a patch antenna, a loop antenna, a monopole antenna, a slot antenna, or the like. The number of antennas may be four or more. The fixing place of the antenna is not limited to that of this embodiment. In any case, if the antenna is arranged in the vehicle so that at least three spatially orthogonal polarization directions exist, substantially the same effect can be obtained.

As described above, in the seventh embodiment of the present invention, since the in-vehicle radio communication device is provided with the three antennas whose polarization directions are orthogonal to each other, polarization diversity reception is possible and the mobile station The in-vehicle wireless communication between the fixed station and the mobile station can be satisfactorily performed regardless of the polarization direction.

[0067]

As is apparent from the above description, according to the present invention, there is provided an in-vehicle wireless communication device installed at a predetermined place in the vehicle so as to perform wireless communication with a mobile terminal in the vehicle.
A plurality of antennas arranged so that the polarization directions are different,
Since the diversity means for selecting or synthesizing the received signals of the plurality of antennas is provided, it is possible to obtain the effect that the polarization diversity reception can be performed and the in-vehicle wireless communication between the fixed station and the mobile station can be favorably performed.

Further, a plurality of antennas arranged at a predetermined interval and a plurality of antennas are provided in an in-vehicle wireless communication device installed at a predetermined place in the vehicle so as to perform wireless communication with a mobile terminal in the vehicle. Since the diversity means for selecting or synthesizing the received signal of the antenna is provided, there is an effect that spatial diversity reception can be performed and excellent in-vehicle wireless communication between the fixed station and the mobile station can be performed.

Further, a plurality of antennas arranged so as to have different maximum radiation directions and a plurality of antennas are arranged in an in-vehicle wireless communication device installed at a predetermined place in the vehicle so as to perform wireless communication with a mobile terminal in the vehicle. Since it is provided with the diversity means for selecting or synthesizing the reception signal of the antenna, the directional diversity reception can be performed, and the in-vehicle wireless communication between the fixed station and the mobile station can be favorably performed.

Further, since the plurality of antennas are provided in the vicinity of the display portion of the information communication terminal device installed in the vehicle, which is directed toward the passenger compartment, the antennas can be downsized and the structure of the fixed station can be simplified. With the diversity reception, there is an effect that the in-vehicle wireless communication between the fixed station and the mobile station can be favorably performed.

In addition, a one-wavelength loop antenna having a plurality of feeding points and a plurality of feeding points are provided in an in-vehicle wireless communication device installed at a predetermined location in the vehicle so as to perform wireless communication with a mobile terminal in the vehicle. And a means for selecting one of the two are provided, the effect that the in-vehicle wireless communication between the fixed station and the mobile station can be satisfactorily achieved by the polarization diversity reception is obtained.

Further, since the one-wavelength loop antenna is provided in the vicinity of the display portion facing the passenger compartment of the information communication terminal device installed in the vehicle, the antenna can be downsized and the structure of the fixed station can be simplified. At the same time, there is an effect that the in-vehicle wireless communication between the fixed station and the mobile station can be favorably performed by the polarization diversity reception.

Since the plurality of antennas are three antennas whose polarization planes are orthogonal to each other, the effect that the in-vehicle wireless communication between the fixed station and the mobile station in the vehicle can be satisfactorily achieved is obtained.

Further, it is an in-vehicle wireless communication device which is used in a system for performing wireless communication between at least two points in the vehicle, and which is installed in a predetermined place in the vehicle. With multiple antennas aimed at,
Since a means for selecting a plurality of antennas is provided, even if the radio wave of one antenna is blocked, another antenna can receive the signal, and the in-vehicle wireless communication between the fixed station and the mobile station can be favorably performed. Is obtained.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of an in-vehicle wireless communication device according to a first embodiment of the present invention,

FIG. 2 is a diagram showing radio wave propagation characteristics (reception level) by the in-vehicle wireless communication device according to the first embodiment;

FIG. 3 is a diagram showing radio wave propagation characteristics (cumulative probability distribution) by the in-vehicle wireless communication device according to the first embodiment;

FIG. 4 is a basic configuration diagram of an in-vehicle wireless communication device according to a second embodiment,

FIG. 5 is a diagram showing radio wave propagation characteristics (reception level) by the in-vehicle wireless communication device according to the second embodiment;

FIG. 6 is a diagram showing radio wave propagation characteristics (cumulative probability distribution) by the in-vehicle wireless communication device according to the second embodiment;

FIG. 7 is a basic configuration diagram of an in-vehicle wireless communication device according to a third embodiment,

FIG. 8 is a diagram showing details of a basic configuration of an in-vehicle wireless communication device according to the third embodiment;

FIG. 9 is a diagram showing directivity of an in-vehicle wireless communication device according to the third embodiment;

FIG. 10 is a diagram showing radio wave propagation characteristics (reception level) by the in-vehicle wireless communication device according to the third embodiment;

FIG. 11 is a diagram showing radio wave propagation characteristics (cumulative probability distribution) by the in-vehicle wireless communication device according to the third embodiment;

FIG. 12 is a basic configuration diagram of an in-vehicle wireless communication device according to a fourth embodiment,

FIG. 13 is a basic configuration diagram of an in-vehicle wireless communication device according to a fifth embodiment,

FIG. 14 is a basic configuration diagram of an in-vehicle wireless communication device according to a sixth embodiment,

FIG. 15 is a basic configuration diagram of an in-vehicle wireless communication device according to a seventh embodiment.

[Explanation of symbols] 11,12,71,151 dipole antenna 13,134,152 Comparative selection device 14,135 transceiver 15 Diversity device 16,123,137 front panel 72 Open-ended diamond antenna 73,121 Conductor plate 74 Center console 75,77 feeding point 76,78 Ground point 122,136 Display screen section 131 loop antenna 132,133 Selector 141,142 Antenna

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masami Makino             3-1, Tsunashima-Higashi 4-chome, Kohoku-ku, Yokohama-shi, Kanagawa             Matsushita Communication Industry Co., Ltd. (72) Inventor Koichi Asaoka             3-1, Tsunashima-Higashi 4-chome, Kohoku-ku, Yokohama-shi, Kanagawa             Matsushita Communication Industry Co., Ltd. F term (reference) 5K059 CC03 CC04 CC05 DD02 DD10                       DD24 DD27 DD37                 5K067 AA42 BB04 CC24 EE02 EE10                       EE22 KK02 KK03

Claims (9)

[Claims] 1. An in-vehicle wireless communication device installed at a predetermined location in a vehicle so as to perform wireless communication with a mobile terminal in the vehicle, and a plurality of antennas arranged so as to have different polarization directions, An in-vehicle wireless communication device, comprising: diversity means for selecting or combining received signals of a plurality of antennas. 2. An in-vehicle wireless communication device installed at a predetermined place in a vehicle so as to wirelessly communicate with a mobile terminal in the vehicle, and a plurality of antennas arranged at predetermined intervals, and the plurality of antennas. In-vehicle wireless communication device, comprising: diversity means for selecting or synthesizing a received signal from the antenna. 3. An in-vehicle wireless communication device installed at a predetermined place in a vehicle to perform wireless communication with a mobile terminal in the vehicle, and a plurality of antennas arranged so that maximum radiation directions are different, An in-vehicle wireless communication device, comprising: diversity means for selecting or combining received signals of a plurality of antennas. 4. The antenna according to claim 1, wherein the plurality of antennas are provided in the vicinity of a display portion of the information communication terminal device installed in the vehicle, which is directed toward the passenger compartment. In-vehicle wireless communication device. 5. A one-wavelength loop antenna having a plurality of feeding points, and the plurality of power feedings in an in-vehicle wireless communication device installed at a predetermined location in the vehicle so as to wirelessly communicate with a mobile terminal in the vehicle. And a means for selecting one of the points. 6. The in-vehicle wireless communication according to claim 5, wherein the one-wavelength loop antenna is provided in the vicinity of a display portion of the information communication terminal device installed in the vehicle, which is directed toward a vehicle compartment. apparatus. 7. The in-vehicle wireless communication device according to claim 1, wherein the plurality of antennas are three antennas whose polarization planes are orthogonal to each other. 8. An in-vehicle wireless communication device, which is used in a system for performing wireless communication between at least two points in a vehicle and is installed at a predetermined place in the vehicle, wherein directivity is provided in a plurality of areas in a vehicle compartment. An in-vehicle wireless communication device comprising a plurality of antennas directed to the antenna, and means for selecting the plurality of antennas. 9. A vehicle, comprising: the in-vehicle wireless communication device according to claim 1; and a mobile terminal that mutually wirelessly communicates with the in-vehicle wireless communication device in the vehicle. Internal wireless communication system.