JP2007132089A - Communication equipment for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide communication equipment for a vehicle, which employs an RFID capable of forming a desired ID reachable area. <P>SOLUTION: This communication equipment for the vehicle comprises: an on-vehicle machine 1 which is installed in the vehicle so as to emit an RF radio wave; an ID transmitter (RF tag) 2 which can carry out communications when receiving the electric power of the RF radio wave emitted from the on-vehicle machine 1, so as to transmit a transmitter ID stored in the transmitter itself; and a portable machine 3 which transmits the received ID to the on-vehicle machine 1, when receiving the transmitter ID transmitted from the ID transmitter 2. Additionally, the on-vehicle machine 1 determines a position of the portable machine 3 on the basis of the transmitter ID which is transmitted from the portable machine 3, and controls the operation of the prescribed section of the vehicle by using the transmitter ID which is transmitted from the portable machine 3. The ID transmitter 2 is installed in a position and a direction, in which electric power equivalent to/exceeding a minimum level required for the operation of the ID transmitter 2 is received from the on-vehicle 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a communication device for a vehicle having a position specifying function of a portable device, and in particular, a passive entry system (smart that can easily operate locking and unlocking of a vehicle door only by holding the portable device. The present invention relates to a vehicle communication device suitable for application of an entry system).

Conventionally, as a vehicle communication device for remotely controlling an in-vehicle device of an automobile, the vehicle door is automatically unlocked when the user carrying the portable device approaches the vehicle, and when the user leaves the vehicle, the vehicle door A vehicle communication device having a function of automatically locking is proposed.
However, in such a conventional apparatus, when the portable device is in the vehicle, measures are taken so that the door is not automatically locked in order to prevent the portable device from being confined.
Therefore, if the user leaves the vehicle without leaving the portable device in the vehicle, the door is left unlocked, which is a problem in crime prevention.
Therefore, when the user leaves the vehicle, if the portable device is left behind in the vehicle, it is necessary to notify the user of the state. That is, a function for determining whether the portable device is inside or outside the vehicle is required.

As a technique for determining whether or not the portable device is in the vehicle (hereinafter referred to as “inside / outside determination technique”), for example, vehicle communication using LF (Low Frequency) charged waves having a frequency of about 120 KHz to 135 KHz. An apparatus (on-vehicle equipment remote control system) has been proposed. (For example, see Patent Document 1)
According to the vehicle inside / outside determination technology using LF charged waves, antennas that emit LF charged waves (hereinafter referred to as “LF band antennas”) are installed at various locations in the vehicle. The in-vehicle device is connected via a wire to supply a frequency of 1.
The portable device is designed to react when the portable device exists within a predetermined magnetic field intensity of the radiated radio wave from the LF band antenna, and the in-vehicle device responds to the designated LF band antenna from the portable device. Thus, the presence of the portable device is determined.

On the other hand, RFID (Radio Frequency Identification) technology is known as a technology for detecting an object using radio waves (see, for example, Non-Patent Document 1).
As technologies related to RFID, there are technologies called by various names such as wireless tags, IC tags, RF tags, ID tags, and the like.
An RFID system is typically composed of an RF (Radio Frequency) tag and a reader / writer, and when both are present in a communicable range, if radio waves are emitted from the reader / writer to the RF tag, an ID (IDENTIFICATION: Identification information) is transmitted, and the reader / writer receives the ID, whereby the reader / writer can obtain information on the presence of the RF tag and the ID.

Further, in the above-mentioned vehicle interior / external determination technique of Patent Document 1, the in-vehicle device and the LF band antenna are connected by wire, but the technique of Non-Patent Document 1 is applied to replace the LF band antenna, for example, an RF tag. A device that determines the inside / outside of the portable device using the unique ID of the RF tag by wirelessly communicating between the RF tag and the vehicle-mounted device is conceivable.
According to this type of vehicle inside / outside determination device, an RF tag installed at an appropriate position in a vehicle uses a radio wave power received from an antenna of an in-vehicle device, and uses its own tag ID as an ID reachable area. The portable device that transmits and exists in the ID reachable area transmits the received tag ID to the in-vehicle device.
When the in-vehicle device recognizes that the tag ID transmitted from the portable device has been received, the in-vehicle device can determine in which RF tag ID reachable area the portable device exists.

In this case, the RF tag is arranged at a plurality of locations in the vehicle in consideration of the power radiation area from the vehicle-mounted device antenna, and the vehicle-mounted device has a unique ID for each RF tag in the power radiation area. It is designed to supply enough power to transmit.
That is, the in-vehicle device radiates radio waves to the power radiation area via the antenna, and the RF tag in the power radiation area transmits each unique ID to the nearby ID reachable area using the received power of the radio waves. The portable device in the ID reachable area receives the unique ID from the RF tag and transmits it to the in-vehicle device.
Then, the in-vehicle device determines which RF tag the portable device exists in accordance with which unique ID is received by the portable device, and whether the portable device exists inside or outside the vehicle. Will be determined.
Japanese Patent Laying-Open No. 2003-221954 (FIG. 3, paragraphs 0031 to 0034) RFID Handbook <2nd edition> “Principle and application of contactless IC card” [Klaus Finkenzeller, translated by Soft Engineering Institute, published by Nikkan Kogyo Shimbun, Ltd.] (110 pages to 111 pages, Figure 4.74)

In the above-described conventional vehicle communication device using RFID, the RF tag supplies sufficient power to transmit the unique ID held by the RF tag. Arranged in multiple places.
However, when the antenna polarization direction of the RF tag is installed out of the polarization direction at the installation position, the RF tag can efficiently receive the radio wave radiated by the vehicle-mounted device antenna due to the polarization loss. The desired ID reachable area cannot be formed.
Further, when the RF tag is installed close to a conductor such as a vehicle, the antenna impedance of the RF tag changes, so that not only the power feeding loss to the antenna increases and the radiated power decreases, but also the conductor Because the radiation pattern of the RF tag antenna changes depending on the distance between the desired ID area and the desired ID reachable area cannot be formed.

  The present invention has been made to solve the above-described problems, and an RFID capable of forming a desired ID reachable area by optimally arranging an RF tag as an ID transmitter in a vehicle. An object of the present invention is to obtain a vehicular communication device using the.

  A vehicle communication device according to the present invention is installed in a vehicle and radiates a radio wave, and can communicate with a transmitter installed in the vehicle and receive power of a radio wave radiated from the transmitter. When the ID transmitter that transmits the stored transmitter ID and the transmitter ID that is normally carried by the vehicle user and transmitted by the ID transmitter is received, the received ID is transmitted to the transmitter. And the transmitter determines the position of the receiver based on the transmitter ID transmitted from the receiver and transmits the transmitter from the receiver. In the vehicle communication device that controls the operation of the predetermined part of the vehicle by using the ID, in a position and a direction for receiving the power of the minimum level or more necessary for the ID transmitter to operate from the transmitter, Above It is intended to place the D transmitter.

  According to the vehicle communication device of the present invention, the ID transmitter is installed at a position and a direction for receiving the electric power of the minimum level or more necessary for the operation of the ID transmitter. An ID reachable area of a desired size can be formed within the operating range.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the drawings, the same reference numerals represent the same or equivalent ones.
Embodiment 1 FIG.
1 is a block diagram showing a configuration of a vehicle communication device according to Embodiment 1 of the present invention.
As shown in the figure, the vehicle communication device is composed of an in-vehicle device 1 that can communicate with each other, an RF (Radio Frequency) tag 2 and a portable device 3, and the in-vehicle device 1 and the RF tag 2 are installed in the vehicle. Is done.
The in-vehicle device 1 is capable of mutual communication between the RF tag 2 and the portable device 3, and can transmit a power supply radio wave to the RF tag 2 or receive a radio wave from the portable device 3. it can.

The in-vehicle device 1 installed in the vehicle includes an antenna 11 for transmitting power supply radio waves to the RF tag 2 installed in the vehicle, and an antenna 12 for receiving radio waves from the portable device 3. And an electronic control unit 13 connected to the antenna 11 and the antenna 12.
The electronic control unit 13 controls transmission of radio waves from the antenna 11 and controls each part of the vehicle based on a signal received by the antenna 12 (for example, control of locking or unlocking the vehicle door).
Although FIG. 1 shows a case where the antennas 11 and 12 are individual antennas, the antennas 11 and 12 may be configured by the same antenna.

The RF tag 2 functions as an ID (identification information) transmitter, and transmits a transmitter ID held by itself in response to reception of a radio wave from the in-vehicle device 1.
Therefore, the RF tag is also referred to as an ID transmitter.
1 shows a case where a plurality of RF tags 201, 202, 203,... 2n are used as the RF tag 2, but one RF tag 2 (single or plural cases are generic names). And may be referred to as “RF tag 2”.
In addition, the use frequency of the RF tag 2 (201, 202, 203,... 2n) is suitable in the 950 MHz band or 2.45 GHz band, but may be in a high frequency band, and these frequencies (that is, 950 MHz) are not necessarily required. Band or 2.45 GHz band frequency).
Although not shown, the RF tags 2 (201, 202, 203,... 2n) are, for example, an antenna and an antenna circuit that receive radio waves from the vehicle-mounted device 1, and power generation that extracts power from the received radio waves. A circuit, various circuits that operate with the generated power, and a transmission circuit that transmits the transmitter ID as a radio wave are provided.
The in-vehicle device 1 and the portable device 3 are designed according to the frequency of the RF tag 2 to be used.

The portable device 3 has a shape that can be easily carried by a user, and includes an antenna 31 for receiving a transmitter ID transmitted from the RF tag 2 and an antenna 32 for transmitting data to the in-vehicle device 1.
The transmitting antenna 32 of the portable device 3 constitutes ID communication means in association with the receiving antenna 12 of the in-vehicle device 1, and the ID communication means is a transmitter from the portable device 3 toward the in-vehicle device 1. Send ID.
In addition, although the antennas 31 and 32 are each comprised by the separate antenna so that transmission / reception between the RF tag 2 and the vehicle equipment 1 is possible, they may be comprised by the same antenna.

Next, a schematic operation according to the first embodiment of the present invention shown in FIG. 1 will be described.
First, the in-vehicle device 1 installed in the vehicle radiates radio waves to at least one RF tag 2 installed in a proper place of the vehicle.
The RF tag 2 uses the power generated by the power generation circuit described above to transmit a unique transmitter ID held by itself.
On the other hand, the portable device 3 possessed by the user receives the transmitter ID from the RF tag 2 and transmits the transmitter ID from the portable device 3 to the in-vehicle device 1 via the ID communication means.

Finally, the in-vehicle device 1 determines the position of the portable device 3 based on the transmitter ID received from the portable device 3.
That is, by setting the communicable areas (reachable range of transmitter IDs) 401 to 405 of the RF tags 201 to 205 so as not to exist outside the vehicle, the portable device 3 existing outside the vehicle can be set to the transmitter ID. Can not receive.
Therefore, whether the portable device 3 exists in the vehicle or outside the vehicle can be determined depending on whether the portable device 3 receives the transmitter ID.
The RF tag 2 that functions as an ID transmitter may be a device having a function of receiving an electric wave from the outside and transmitting an ID, but in this embodiment, the RF tag 2 is used as shown in FIG. The case will be described.

Next, how power and data are exchanged between the in-vehicle device 1, the RF tag 2, and the portable device 3 via radio waves will be described.
First, the vehicle-mounted device 1 supplies power to, for example, the RF tag 2n by radiating radio waves from the transmitting antenna 11.
The RF tag 2n that has received the radio wave radiation has voltage extraction means using a known technique called Rectenna, and rectifies the received radio wave to extract the voltage, and the RF tag 2n uses the extracted voltage to extract the voltage. The internal circuit is operated, and the transmitter ID held by the RF tag 2n is transmitted by radio waves.
The rectenna (Rectenna = Rectifier + Antenna) is a circuit (antenna) that extracts DC energy from AC energy of received radio waves.
At this time, the carrier wave used for transmitting the transmitter ID may be supplied from the vehicle-mounted device 1 or may be generated by the RF tag 2n oscillating internally.
The portable device 3 receives the transmitter ID transmitted from the RF tag 2n.

Here, the communicable area between the RF tag 2n and the portable device 3 will be described.
FIG. 2 is a diagram for explaining the reachable range (communication area 4n) of the transmitter ID from the RF tag 2n.
In FIG. 2, a circular frame 4n indicated by a two-dot chain line indicates a reachable range of the transmitter ID from the RF tag 2n (that is, a communicable area where the portable device 3 can receive the transmitter ID of the RF tag 2n). ing.
The reachable range (communication area 4n) of the transmitter ID from the RF tag 2n depends on the power of the carrier used for the RF tag 2n to transmit the transmitter ID.
Therefore, when the carrier wave is supplied from the in-vehicle device 1, it is necessary to receive from the in-vehicle device 1 sufficient power to realize the desired communicable area 4 n.

The portable device 3 can receive the transmitter ID when it exists inside the communicable area 4n of the RF tag 2n, but cannot receive the transmitter ID when it exists outside the communicable area 4n.
The portable device 3 existing in the communicable area 4n transmits the received transmitter ID from the antenna 32 to the vehicle-mounted device 1 by radio waves.
The in-vehicle device 1 can recognize that the portable device 3 exists in the communicable area 4n of the RF tag 2n based on the transmitter ID transmitted from the portable device 3.

Next, the arrangement state and operation of the RF tag 2 when the RF tag 2 is installed in the interior of the vehicle and it is determined that the portable device 3 exists in the vehicle will be described.
FIG. 3 is a plan view showing an installation state of the RF tags 201 to 205 on the vehicle 5, schematically showing an image of the vehicle 5 viewed from directly above.
In FIG. 3, the vehicle-mounted device 1 is mounted in the vehicle 5, and RF tags 201 to 205 are installed in the interior of the vehicle 5.
Each of the RF tags 201 to 205 has a communicable area 401 to 405 (a reachable range of the transmitter ID).
The RF tags 201 to 205 are installed, for example, in the interior of the door portion of the vehicle 5 so that the positions shown in FIG.

As can be seen from FIG. 3, when the communicable areas 401 to 405 of the RF tags 201 to 205 are overlapped, it is understood that the entire area in the vehicle 5 is covered.
That is, the first arrangement condition of the RF tags 201 to 205 is to cover the entire area in the vehicle 5 as shown in FIG.
In addition, as a setting condition of the communicable areas (transmitter ID reachable ranges) 401 to 405 of the RF tags 201 to 205, it can be mentioned that they do not exist outside the vehicle 5.
That is, the second arrangement condition of the RF tags 201 to 205 is that the portable device 3 (see FIGS. 1 and 2) existing outside the vehicle 5 cannot receive the transmitter ID.

In order to satisfy the above-described first arrangement condition and second arrangement condition regarding the RF tags 201 to 205, for example, it is effective to install the RF tags 201 to 205 in the interior lower than the window glass of the vehicle 5 It is.
However, as long as the first and second arrangement conditions are satisfied, the number and position of the RF tags 201 to 205 are not necessarily the same as those shown in FIG.
The RF tags 201 to 205 and the in-vehicle device 1 are arranged in the vehicle 5 so as to satisfy the above conditions, and the transmitter ID transmitted from the RF tags 201 to 205 in response to the radiated radio wave from the in-vehicle device 1 is a portable device. 3 is configured to communicate the received transmitter ID from the portable device 3 to the in-vehicle device 1.
Thereby, the vehicle equipment 1 can determine that the portable device 3 exists in the vehicle 5 when the transmitter ID from the portable device 3 is received.
The RF tags 201 to 205 may be affixed to the interior surface such as a seat, an instrument panel, a floor, or a ceiling of the vehicle 5 or may be installed so as to be embedded in the interior.

Next, the direction in which the RF tag 2n is installed will be described in detail.
When there is no radio wave reflector near the RF tag 2n and the RF tag 2n is present in the beam directing direction of the vehicle-mounted device antenna 11, the antenna polarization direction of the RF tag 2n is the polarization of the vehicle-mounted device antenna 11. If the RF tag 2n is installed so as to coincide with the direction, the RF tag 2n can efficiently receive the radio wave radiated from the vehicle-mounted device antenna 11.
FIG. 4 schematically shows an RF tag installation state when the RF tag 2n is installed so that the antenna polarization direction of the RF tag 2n, which is an ID transmitter, matches the polarization direction of the vehicle-mounted device antenna 11. FIG.
In this case, as shown in FIG. 4, the vehicle-mounted device antenna 11 has a unidirectional radiation pattern 61 and is an antenna that emits less light in the wide-angle and rear direction, and the RF tag 2 n emits less radio waves. It is installed not in a direction (for example, a wide-angle direction or a back surface direction) but in a direction (for example, a front direction) in which radio waves are emitted.

Specifically, when the vehicle-mounted device antenna 11 having the unidirectional radiation pattern 61 is installed on the vehicle ceiling and a transmission radio wave is radiated downward from the vehicle, the RF tag 2n is connected to the vehicle seat or center. This corresponds to the case where it is installed in the console section.
By installing the RF tag 2n in such a position and direction, the influence of the direct wave 62 in the radio wave received by the RF tag 2n out of the radio wave radiated by the vehicle-mounted device antenna 11 is increased, and the polarization direction fluctuation due to reflection is increased. It becomes difficult to be affected by.
That is, as shown in FIG. 4, by installing the RF tag 2 n so that the antenna polarization direction of the RF tag 2 n matches the antenna polarization direction of the vehicle-mounted device antenna 11, the vehicle-mounted device 1 is connected to the vehicle-mounted device 1. The power transmitted from 11 can be received efficiently, and power saving can be realized.

Therefore, the maximum communication area can be formed at a predetermined installation position of the RF tag 2n only by changing the installation direction of the RF tag 2n so as to coincide with the polarization direction of the vehicle unit antenna 11.
Conversely, when the RF tag 2n is installed in a direction in which the antenna polarization direction of the RF tag 2n is orthogonal to the antenna polarization direction of the vehicle-mounted device antenna 11, the efficiency of the RF tag 2n receiving the transmission power of the vehicle-mounted device 1 is the highest. It becomes low, and the minimum communication area can be formed at the predetermined installation position of the RF tag 2n by changing the installation direction of the RF tag 2n to be orthogonal to the polarization direction of the antenna 11 of the vehicle-mounted device 1.

On the other hand, when there is a radio wave reflector in the vicinity of the RF tag 2n or when the RF tag 2n is not present in the beam directing direction of the vehicle-mounted device antenna 11, the RF tag 2n that can receive the transmission power of the transmitter at the maximum. The antenna polarization direction does not always coincide with the polarization direction of the vehicle-mounted device antenna 11.
FIG. 5 is a conceptual diagram schematically showing an installation state of the RF tag when there is a radio wave reflector (for example, the vehicle conductor 64) in the vicinity of the RF tag 2n.
FIG. 6 is a conceptual diagram schematically showing an installation state of the RF tag when the RF tag 2n does not exist in the beam directing direction of the vehicle-mounted device antenna 11.
In FIG. 5 or FIG. 6, 63 is an indirect wave (multipath) received via one or more reflection points.
In FIG. 6, the vehicle-mounted device antenna 11 has a unidirectional radiation pattern 61 and is an antenna that emits less radiation in the wide-angle, rear direction, and does not radiate radio waves rather than in a direction in which radio waves are radiated in a large amount (for example, the front direction). A case is shown in which the RF tag 2n is installed in a direction in which there is little (for example, a wide angle direction or a back direction).

In the case where one of the two conditions described above (that is, one of the conditions shown in FIG. 5 or FIG. 6) is satisfied, the influence of the indirect wave (multipath) 63 received through one or more reflection points is reduced. Since it cannot be ignored and is easily affected by fluctuations in the polarization direction due to reflection in radio wave propagation in the vehicle, the antenna polarization direction of the RF tag 2n that can receive the maximum transmission power of the transmitter is the polarization direction of the vehicle-mounted device antenna 11. Does not necessarily match.
Therefore, when installing the RF tag 2n in such a place, the RF tag 2n is transmitted by the transmitter by installing the RF tag 2n in a direction in which the maximum power can be received based on the actually measured electric field strength. It is possible to efficiently receive power to be saved and to realize power saving.
Thus, according to Embodiment 1, in the vehicle communication device using the RF tag, when the influence of the indirect wave is small and the influence of the direct wave is large, the antenna polarization direction of the RF tag 2n is the in-vehicle device. By installing the RF tag 2n so as to coincide with the polarization direction of the antenna 11, the RF tag 2n can efficiently receive the radio wave radiated from the vehicle-mounted device antenna 11, and can realize power saving.

As described above, according to the vehicle communication device of the present embodiment, the in-vehicle device 1 that is a transmitter installed in the vehicle and radiates radio waves (RF radio waves), and the in-vehicle device installed in the vehicle. (Transmitter) An ID transmitter (RF tag) 2 that can communicate when receiving power of radio waves radiated from the transmitter 1 and transmits a transmitter ID stored in itself, and is usually carried by a vehicle user. When the transmitter ID transmitted from the ID transmitter 2 is received, the portable terminal (receiver receiving the transmitter ID) 3 transmits the received ID to the vehicle-mounted device (transmitter) 1. Further, the in-vehicle device (transmitter) 1 determines the position of the portable device (receiver) 3 based on the transmitter ID transmitted from the portable device (receiver) 3 and the portable device (transmitter) 1 Using the transmitter ID transmitted from the machine (receiver) 3 In the vehicle communication device that controls the operation of the predetermined part of the vehicle, the vehicle receives a power of at least a minimum level necessary for the operation of the ID transmitter (RF tag) 2 from the in-vehicle device (transmitter) 1. The ID transmitter 2 is installed at the position and direction to be operated.
Therefore, an ID reachable area of a desired size can be formed within a range in which the ID transmitter (RF tag) 2 operates.
In this embodiment, “in-vehicle device” and “portable device” are expressions indicating components on the application side. If functional expressions are performed, “in-vehicle device” is “transmitter”, “mobile device” "Machine" means "receiver".

Moreover, according to the vehicle communication device according to the present embodiment, since the ID transmitter 2 is installed at a position and direction where the ID transmitter 2 receives the maximum power, the radio wave transmitted by the in-vehicle device 1 is transmitted as an ID. It becomes possible for the machine 2 to efficiently receive, and power saving can be realized.
Moreover, since the vehicle communication apparatus according to the present embodiment installs the ID transmitter 2 at a position and a direction for receiving the minimum level of power required for the operation of the ID transmitter 2, the ID transmitter The smallest ID reachable area can be formed within the range in which 2 operates.
In addition, according to the vehicle communication device according to the present embodiment, the antenna polarization direction of the ID transmitter 2 is a direction in which the electric power exceeding the minimum level necessary for the operation of the ID transmitter is received. In addition, since the ID transmitter 2 is installed, an ID reachable area having a desired size can be formed within a range in which the ID transmitter 2 operates.

Further, according to the vehicle communication device of the present embodiment, the ID transmitter 2 is installed so that the antenna polarization direction of the ID transmitter 2 is the direction in which the ID transmitter 2 receives the maximum power. Therefore, the ID transmitter 2 can efficiently receive the radio wave transmitted by the in-vehicle device 1, and power saving can be realized.
Further, according to the vehicle communication device of the present embodiment, the ID transmitter 2 is installed so that the antenna polarization direction of the ID transmitter 2 is the direction in which the ID transmitter 2 receives the minimum power. Therefore, the maximum ID reachable area can be formed at the position where the ID transmitter 2 is installed.
Further, according to the vehicle communication device of the present embodiment, the antenna polarization direction of the ID transmitter 2 is set to a direction for receiving the minimum level of power required for the operation of the ID transmitter 2. Therefore, the smallest ID reachable area can be formed within the range in which the ID transmitter 2 operates.

Further, according to the vehicle communication device of the present embodiment, the antenna polarization direction of the ID transmitter 2 matches the antenna polarization direction of the in-vehicle device (transmitter) 1 that supplies power to the ID transmitter 2. Since the ID transmitter 2 is installed in the direction, the maximum ID reachable area can be formed at the position where the ID transmitter 2 is installed.
Further, according to the vehicle communication device of the present embodiment, the antenna polarization direction of the ID transmitter 2 is orthogonal to the antenna polarization direction of the in-vehicle device (transmitter) 1 that supplies power to the ID transmitter 2. Since the ID transmitter 2 is installed in the direction in which the ID transmitter 2 is installed, a minimum ID reachable area can be formed at the position where the ID transmitter 2 is installed.

Embodiment 2. FIG.
FIG. 7 is a conceptual diagram schematically showing an installation state of the RF tag in the vehicle communication device according to the second embodiment.
Here, in the vehicle communication device using the RF tag described in detail in the first embodiment, particularly as to the position where the RF tag 2n is installed, particularly the merit of adjusting the separation from the vehicle conductor 64. Details will be described.
First, generally manufactured RF tags operate by transmitting radio waves to both the front and back sides of the surface on which they are installed and receiving radio waves from both sides.
Therefore, when the RF tag 2n is installed in the vicinity of the vehicle conductor 64, as shown in FIG. 5, the direct wave 62 that the RF tag 2n directly transmits / receives from the front side of the installation surface and the vehicle conductor 64 The radio wave combined with the indirect wave 63 that indirectly transmits and receives the radio wave reflected by the back side of the installation surface is transmitted and received.
Therefore, in the radio wave in which the direct wave 62 and the indirect wave 63 are combined, there are directions in which the direct wave and the indirect wave are strengthened and weakened by the phase relationship.

By using the principle described above, the radiation pattern of the antenna can be changed to a desired pattern by adjusting the separation of the RF tag 2n from the vehicle conductor 64.
For example, power can be efficiently transmitted and received between the RF tag 2n and the vehicle-mounted device by directing the maximum gain direction of the antenna of the RF tag 2n toward the vehicle-mounted device antenna.
Furthermore, an optimal communicable area can be formed by adjusting the separation from the vehicle conductor portion 64 according to various positions in the vehicle where the RF tag 2n is installed.
The RF tag 2n can be installed by installing the RF tag 2n on the vehicle conductor 64 via a spacer 71 made of a material that does not affect the propagation of radio waves such as foamed polystyrene. This is suitable for the case where the RF tag 2n is built in the lining portion of the vehicle door, the lining portion of the vehicle ceiling, or the lining portion of the vehicle instrument panel that can ensure a necessary separation from the vehicle conductor portion 64.
That is, in order to form an optimal communicable area, the RF tag 2n needs to maintain a predetermined distance from the vehicle conductor 64, but the lining portion of the vehicle door, the lining portion of the vehicle ceiling, By incorporating the RF tag 2n in the lining portion of the vehicle instrument panel, the distance from the vehicle conductor 64 can be easily set to a desired distance.
The instrument panel is an abbreviation for an instrument panel, and is a panel containing instruments (instruments) in front of the driver's seat.

First, a method for adjusting the power received by the RF tag 2n using the antenna impedance that changes depending on the separation of the RF tag 2n from the vehicle conductor 64 will be described.
When the RF tag 2n is installed close to the vehicle conductor portion 64 at less than 1/30 wavelength in the use frequency, the antenna impedance matching state of the RF tag 2n is deteriorated, so that loss in antenna feeding occurs.
For this reason, the received power of the RF tag 2n is reduced by the amount of the power supply loss, and the communication area is small compared to the case where the RF tag 2n is installed at a distance of 1/30 wavelength or more from the vehicle conductor 64. Can be formed.
On the other hand, by installing the RF tag 2n on the vehicle conductor 64 with a separation of 1/30 wavelength or more at the use frequency, the maximum transmission direction of the antenna of the RF tag 2n without deteriorating the matching state of the antenna impedance and The maximum receiving direction can be directed to a desired direction.
Thereby, for example, power can be efficiently transmitted and received between the RF tag 2n and the vehicle-mounted device by directing the maximum reception direction or the maximum transmission direction of the antenna of the RF tag 2n toward the vehicle-mounted device antenna.

FIG. 7 is a diagram (vehicle top view) for explaining an example in which the antenna radiation pattern of the RF tag 2n is changed to a desired pattern by changing the distance d between the RF tag 2n and the vehicle conductor 64. In the interior of the vehicle pillar lining 70, the RF tag 2n is separated from the vehicle conductor 64 by a spacer 71 with a separation d (that is, d) that is an integer (n) times a half wavelength (λ / 2) at the use frequency. = N × λ / 2) is a diagram showing a state when installed.
When the RF tag 2n is installed in the vehicle pillar lining 70, interior parts such as the seat back portion 72 are often present at the front position of the RF tag 2n. Therefore, the portable device 3 is located at the front position of the RF tag 2n. Can not exist.
On the other hand, as shown in FIG. 7, the antenna radiation pattern of the RF tag 2n installed so that the distance from the vehicle conductor portion 64 is an integral multiple of a half wavelength is in the normal direction of the sticking surface of the RF tag 2n. The power radiation becomes null, and the maximum radiation direction can be given in an oblique direction with respect to the pasting surface.

“Null” means that the gain of the antenna is low (does not radiate radio waves).
If the distance d between the conductor (vehicle conductor portion) and the RF tag is an integral multiple of a half wavelength, the reflected wave from the conductor and the direct wave from the RF tag are weakened in the direct path between the conductor and the RF tag. In the front (normal) direction, the radio wave emission of the RF tag is null.
On the other hand, with respect to the oblique direction, there is a direction in which the phases are strengthened due to the path difference, and therefore the maximum radiation direction can be provided in the oblique direction.
The condition of whether the phase of the reflected wave from the conductor and the direct wave from the RF tag intensify or weaken is determined by the path difference in that direction, and the path difference (distance d to the conductor) is an integral multiple of a half wavelength. Weak each other and strengthen each other when there is an odd multiple of a quarter wavelength.
In the RF tag 2n installed state as shown in FIG. 7, unnecessary radio wave radiation is prevented from being emitted to the front position of the RF tag 2n where the seat backrest portion 72 and the like exist, and the RF tag in which the portable device 3 can actually exist. It is possible to form a communicable area 4n extending in the 2n diagonal direction.
Therefore, it is possible to efficiently transmit and receive radio wave power between the RF tag 2n and the portable device 3, and it is possible to reduce the number of RF tags 2n to be originally installed.
In the above description, a preferred example of improving the efficiency of power transmission / reception between the RF tag 2n and the portable device 3 has been described. However, the power between the RF tag 2n and the vehicle-mounted device antenna 11 existing in two different directions is described. The present invention can also be applied to improve the efficiency of transmission / reception.

As described above, according to the second embodiment of the present invention, in the vehicle communication device using the RF tag, even if it is a general-purpose RF tag having a uniform radiation pattern, the RF tag is separated from the vehicle conductor. By changing the radiation pattern of the RF tag antenna, it is possible to realize an optimum radiation pattern, that is, an optimum communicable area according to the vehicle position where the RF tag is installed.
Further, not only can radio wave transmission / reception between the RF tag and the portable device or between the RF tag and the vehicle-mounted device be made efficient, but the number of RF tags that should be originally installed can be reduced.

As described above, according to the vehicle communication device according to the present embodiment, the ID transmitter 2 is connected to the vehicle conductor by a distance that allows the ID transmitter 2 to receive power of a minimum level or more necessary for the operation of the ID transmitter 2. Since it is installed away from the unit 64, an optimal radiation pattern, that is, an optimal communicable area can be realized according to the vehicle position where the ID transmitter 2 is installed.
Further, not only can the radio wave transmission / reception between the ID transmitter (RF tag) 2 and the portable device 3 or the ID transmitter (RF tag) 2 and the vehicle-mounted device 1 be made efficient, but also the ID transmission that should be originally installed. The quantity of the machine (RF tag) 2 can be reduced.

In addition, according to the vehicle communication device of the present embodiment, the distance between the ID transmitter 2 and the vehicle conductor 64 is a distance that is an integral multiple of a half wavelength at the use frequency of the ID transmitter 2. The front direction of the antenna of the machine 2 can be the null direction of power radiation.
Moreover, according to the vehicle communication device according to the present embodiment, the distance between the ID transmitter 2 and the vehicle conductor 64 is equal to or greater than 1/30 wavelength of the use frequency of the ID transmitter 2, so the vehicle-mounted device 1 The ID transmitter 2 can efficiently receive the radio wave transmitted by the transmitter, which can realize power saving and an ID reachable area of a desired size within the range in which the ID transmitter 2 operates. Can be formed.
Moreover, according to the vehicle communication device according to the present embodiment, the distance between the ID transmitter 2 and the vehicle conductor 64 is less than 1/30 wavelength of the use frequency of the ID transmitter 2. The smallest ID reachable area can be formed within the range in which the machine operates.

Embodiment 3 FIG.
FIG. 8 is a conceptual diagram schematically showing an installation state of the RF tag in the vehicle communication device according to the third embodiment.
FIG. 8 is a diagram (vehicle top view) for explaining another example in which the radiation pattern of the antenna of the RF tag 2n is changed to a desired pattern by changing the distance of the RF tag 2n from the vehicle conductor 64. This shows a state in which the RF tag 2n is installed at a distance that is an odd number (n ') times a quarter wavelength of the use frequency with respect to the vehicle conductor portion 64.
In the present embodiment, a communicable area is formed in the luggage room 74 of the vehicle using the RF tag 2n installed on the rear hatch gate lining 73.

In a vehicle of the kind intended for cargo such as a station wagon, since it is generally long in the front direction of the rear hatch gate where the RF tag 2n is installed, the RF tag 2n installed on the rear hatch gate lining 73 should be formed 3 is required to have a high gain with respect to the front direction of the antenna of the RF tag 2n.
On the other hand, in the present embodiment, as shown in FIG. 8, the RF tag 2 n is installed at a distance that is an odd multiple of a quarter wavelength of the use frequency with respect to the vehicle conductor portion 64, thereby reducing the RF tag 2 n. Since the antenna gain can be increased by 3 dB in the normal (front) direction of the sticking surface of the tag 2n, a long communicable area 4n can be formed in the front direction of the RF tag 2n.
Thereby, not only can radio wave transmission / reception between the RF tag 2n and the portable device 3 be made efficient, but also the number of RF tags 2n that should be originally installed can be reduced.

Thus, according to the present embodiment, even if the vehicle to which the vehicle communication device is applied is a vehicle of the kind intended for freight such as a station wagon, in the vehicle communication device using the RF tag. Even for general-purpose RF tags with a uniform radiation pattern, the radiation pattern of the RF tag antenna can be optimized according to the position of the vehicle where the RF tag is installed by changing the distance from the vehicle conductor of the RF tag. A pattern, that is, an optimal communicable area can be realized.
Further, not only can radio wave transmission / reception between the RF tag and the portable device or between the RF tag and the vehicle-mounted device be made efficient, but the number of RF tags that should be originally installed can be reduced.

  As described above, according to the vehicle communication device of the present embodiment, the distance between the ID transmitter 2 and the vehicle conductor 64 is an odd multiple of a quarter wavelength at the frequency used by the ID transmitter 2. Since the distance is a distance, it is possible to increase the gain of the ID transmitter 2 in the front direction of the antenna, and a long communicable area 4n can be formed in the front direction of the ID transmitter 2.

  The present invention is useful, for example, for realizing a vehicle communication device that can be used in a smart entry system and can form an ID reachable area of a desired size within a range in which an ID transmitter operates.

1 is a block diagram showing a configuration of a vehicle communication device according to Embodiment 1. FIG. It is a figure for demonstrating the reach | attainment range (communication area) of transmitter ID from ID transmitter (RF tag). It is a top view which shows the installation state of ID transmitter to a vehicle. It is a figure which shows typically the state at the time of installing an ID transmitter so that the antenna polarization direction of ID transmitter may correspond with the polarization direction of vehicle equipment antenna. It is a figure which shows typically the installation state of ID transmitter when there exists an electromagnetic wave reflector (vehicle conductor part) in the vicinity of the ID transmitter. It is a figure which shows typically the installation state of ID transmitter when an ID transmitter does not exist in the beam directing direction of a vehicle-mounted apparatus antenna. In the vehicle communication apparatus which concerns on Embodiment 2, it is a figure which shows typically the installation state of ID transmitter. In the vehicle communication apparatus which concerns on Embodiment 3, it is a figure which shows typically the installation state of ID transmitter.

Explanation of symbols

1 In-vehicle device (transmitter)
2, 2n RF tag (ID transmitter)
3 Mobile devices (receivers)
5 Vehicle 11, 12, 31, 32 Antenna 13 Electronic control unit 4n Communicable area 61 On-board unit antenna radiation pattern 62 Direct wave 63 Indirect wave 64 Vehicle conductor part

Claims (15)

A transmitter installed in a vehicle that emits radio waves and a transmitter ID installed in the vehicle that receives radio wave power radiated from the transmitter can communicate and transmit a transmitter ID stored in itself. An ID transmitter and a receiver that is normally carried by a vehicle user and receives the transmitter ID transmitted by the ID transmitter, and transmits the received ID to the transmitter. Further, the transmitter determines the position of the receiver based on the transmitter ID transmitted from the receiver, and uses the transmitter ID transmitted from the receiver to determine the position of the predetermined part of the vehicle. In a vehicle communication device that controls operation,
A vehicular communication apparatus, wherein the ID transmitter is installed at a position and a direction in which electric power of a minimum level or more necessary for the operation of the ID transmitter is received from the transmitter.   The vehicle communication device according to claim 1, wherein the ID transmitter is installed at a position and a direction in which the ID transmitter receives maximum power.   2. The vehicle communication device according to claim 1, wherein the ID transmitter is installed at a position and a direction in which a minimum level of electric power necessary for the operation of the ID transmitter is received.   The ID transmitter is installed such that the antenna polarization direction of the ID transmitter is a direction to receive power of a minimum level or more necessary for the operation of the ID transmitter. The vehicle communication device according to claim 1.   2. The vehicle communication device according to claim 1, wherein the ID transmitter is installed such that an antenna polarization direction of the ID transmitter is a direction in which the ID transmitter receives maximum power. .   2. The vehicle communication device according to claim 1, wherein the ID transmitter is installed so that an antenna polarization direction of the ID transmitter is a direction in which the ID transmitter receives a minimum power. .   2. The vehicle communication according to claim 1, wherein the antenna polarization direction of the ID transmitter is set to a direction for receiving a minimum level of power required for the operation of the ID transmitter. apparatus.   The ID transmitter is installed in a direction in which the antenna polarization direction of the ID transmitter coincides with the antenna polarization direction of the transmitter that supplies power to the ID transmitter. Vehicle communication device.   2. The ID transmitter is installed in a direction in which an antenna polarization direction of the ID transmitter is orthogonal to a polarization direction of an antenna of the transmitter that supplies power to the ID transmitter. The vehicle communication device described.   2. The vehicle according to claim 1, wherein the ID transmitter is installed at a distance from a vehicle conductor portion that can receive electric power of a minimum level or more required for the operation of the ID transmitter. Communication device.   The vehicle communication device according to claim 10, wherein a distance between the ID transmitter and the vehicle conductor is a distance that is an integral multiple of a half wavelength at a frequency used by the ID transmitter.   The vehicle communication device according to claim 10, wherein the distance between the ID transmitter and the vehicle conductor portion is a separation of 1/30 wavelength or more of a use frequency of the ID transmitter.   The distance between the said ID transmitter and the said vehicle conductor part is less than 1/30 wavelength of the utilization frequency of the said ID transmitter, The vehicle communication apparatus of Claim 10 characterized by the above-mentioned.   11. The vehicle communication device according to claim 10, wherein the distance between the ID transmitter and the vehicle conductor is an odd multiple of a quarter wavelength at a frequency used by the ID transmitter.   15. The transmitter according to claim 1, wherein the transmitter is an in-vehicle device installed in a vehicle, and the receiver is a portable device carried by a user of the vehicle. Vehicle communication device.

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