JP4366376B2 - Vehicle communication device - Google Patents

Description

  The present invention relates to a vehicle communication device that determines a region where a portable device used in an electronic key system or the like is present, and more particularly, to a technique applied to a passive entry that opens and closes a vehicle door only by carrying the portable device. About.

  Conventionally, as a device for remotely controlling an in-vehicle device of an automobile, for example, when a user of a vehicle carrying a portable device approaches the vehicle, the vehicle door is automatically unlocked without using the portable device and used. A vehicle communication device has been proposed in which a vehicle door is automatically locked when a person leaves the vehicle.

In the conventional apparatus, in order to prevent the portable device from being confined in the vehicle, it is necessary to prevent the vehicle door from being automatically locked when the portable device is in the vehicle.
That is, it is necessary to determine whether the portable device is inside the vehicle or outside the vehicle.

In order to determine whether or not the portable device is in the vehicle, the conventional in-vehicle device remote control system transmits a code request signal and a confirmation signal for confirming the position of the portable device from the on-vehicle device to the portable device. When the response code returned from the portable device to the in-vehicle device according to the code request signal matches the preset code, the response code is returned from the portable device to the on-vehicle device according to the confirmation signal. Based on the confirmation response signal, the on-vehicle device can be remotely controlled by the portable device.
Here, the confirmation signal includes an activation signal for confirming that the portable device is located in an area where the portable device is in an activated state and a standby signal for confirming that the portable device is located in an area where the portable device is in a standby state. When the portable device receives a standby signal transmitted from the vehicle-mounted device, it does not send back a confirmation response signal, and when it receives only the activation signal transmitted from the vehicle-mounted device, it sends the confirmation response signal to the vehicle-mounted device. Reply to.
The on-vehicle device recognizes that the portable device is located in the area where the standby signal is received when receiving the response code from the portable device, and the portable device receives only the activation signal when receiving the confirmation response signal from the portable device It is possible to remotely control the vehicle-mounted device using a portable device (for example, see Patent Document 1).

In the conventional system, a transmission antenna (hereinafter referred to as “LF band antenna”) that transmits an LF (Low Frequency) charged wave having a frequency of about 120 kHz to 135 kHz, for example, is attached to various parts of the vehicle.
The LF band antenna is connected with a power source and a vehicle-mounted device that supplies a predetermined frequency to the LF band antenna.

On the other hand, RFID (Radio Frequency IDentification) is known as a technique for authenticating an object using radio waves.
RFID is a technology for authenticating a target by attaching an IC chip with an antenna processed into a tag or a label to a thing or a person, and reading information stored in the IC chip with a device called a reader / writer (for example, Non-Patent Document 1).
The technology related to RFID is called by various names such as a wireless tag, an IC tag, an RF tag, and an ID tag.

  In general, an RFID includes an RF tag having a unique tag ID and a reader / writer. When the radio wave is transmitted from the reader / writer to the RF tag when the RF tag and the reader / writer exist within a communicable range, the tag ID is transmitted from the RF tag that has received the radio wave. The reader / writer receives the tag ID and determines an area where the RF tag exists.

Here, by applying the RFID described in Non-Patent Document 1 to the in-vehicle device remote control system described in Patent Document 1, it is determined whether or not the portable device is in the vehicle. It is conceivable to configure the device.
That is, in the said patent document 1, it replaces with the LF band antenna connected to the vehicle equipment by the wire, and the RF tag described in the said nonpatent literature 1 is provided. The vehicle-mounted device is provided with an antenna that transmits and receives radio waves. Thereby, the wiring which connects an onboard equipment and a LF band antenna is abbreviate | omitted.

  At this time, the RF tag is attached to a plurality of locations of the vehicle in consideration of the radiation range of the radio wave transmitted from the antenna of the vehicle-mounted device. Further, the vehicle-mounted device supplies power sufficient to transmit each tag ID to each RF tag within the radio wave emission range. Further, since the radio field intensity of the tag ID transmitted from the RF tag is very small, the reception sensitivity of the portable device is enhanced to the maximum.

  In the vehicle inside / outside determination device, the vehicle-mounted device transmits a radio wave via an antenna. An RF tag within the radio wave emission range transmits a tag ID to a nearby ID reachable area using the radio wave received from the antenna as a power source. When the portable device existing in the ID reachable area receives the tag ID from the RF tag, it demodulates (receives) the received tag ID and transmits it. The on-vehicle device determines which RF tag the portable device is in the vicinity of, based on the tag ID from the portable device, and determines whether the portable device is inside or outside the vehicle.

In the above-described in-vehicle / outside determination device, unlike the above-described general reader / writer, a transmitter (on-vehicle device) that transmits radio waves to an RF tag and a receiver (portable device) that receives a tag ID from the RF tag. And are separated from each other. Therefore, the portable device cannot determine the timing when the RF tag transmits the tag ID.
In addition, various signals are input to the portable device due to noise or the like even when the tag ID is not transmitted from the RF tag. Therefore, the portable device needs to detect a preamble (synchronization) signal that synchronizes processing from signals having various pulse widths. Here, since the reception sensitivity of the portable device is enhanced to the maximum, an event that the portable device erroneously detects noise as a preamble signal and fails to demodulate the tag ID from the RF tag frequently occurs.

JP 2003-221954 A Klaus Finkenzeller, Translated by Software Engineering Laboratory, "RFID Handbook Principle and Application of Contactless IC Card", 2nd edition, Nikkan Kogyo Shimbun, May 31, 2004

In the conventional in-vehicle / outside determination device, the portable device cannot determine the timing at which the RF tag transmits the tag ID. Further, an event frequently occurs in which the portable device erroneously detects noise as a preamble signal and fails to demodulate the tag ID from the RF tag.
For this reason, there is a problem that the demodulation accuracy of the tag ID from the RF tag is low, and the reliability as a vehicle inside / outside determination device is poor.

  An object of the present invention is to solve the above-described problems, and the object of the present invention is to accurately detect a preamble signal even when the vehicle-mounted device and the portable device are separated from each other. Another object of the present invention is to provide a vehicle communication device capable of demodulating a tag ID from an RF tag with high accuracy.

  A vehicle communication device according to the present invention is attached to a plurality of locations of a vehicle, each of which has a plurality of RF tags each having a unique tag ID, a portable device carried by a user of the vehicle, and provided in the vehicle to transmit and receive radio waves. A plurality of RF tags, each of which receives a radio wave transmitted from the antenna, emits a tag ID using the radio wave as a power source. When the tag ID is received, the received tag ID is transmitted, and the vehicle-mounted device transmits a radio wave via the antenna and receives the tag ID from the portable device to determine an area where the portable device exists. The vehicle communication device, the portable device includes a radio wave intensity detecting means for detecting the radio wave intensity of the radio wave from the vehicle-mounted device, and timing for starting the reception processing of the tag ID from the RF tag based on the radio wave intensity It is intended to determine.

According to the vehicle communication device of the present invention, the portable device determines the timing for starting the reception processing of the tag ID from the RF tag, based on the radio wave intensity detected by the radio wave intensity detecting means.
Therefore, even when the vehicle-mounted device and the portable device are separated from each other, the preamble signal can be accurately detected and the tag ID from the RF tag can be demodulated with high accuracy.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding members and parts will be described with the same reference numerals.

Embodiment 1 FIG.
1 is a configuration diagram showing a vehicle 1 equipped with a vehicle communication device according to Embodiment 1 of the present invention.
In FIG. 1, a vehicular communication device is provided in a plurality of RF tags 2 that are attached to a plurality of locations of a vehicle 1 and each have a unique tag ID, a portable device 3 carried by a user of the vehicle 1, and the vehicle 1. And an on-vehicle device 5 to which an antenna 4 for transmitting and receiving radio waves is connected.

The RF tag 2 is attached to a plurality of locations such as the periphery of the door, bonnet, and trunk of the vehicle 1. In FIG. 1, six RF tags 2 are attached to the vehicle 1. However, the present invention is not limited to this, and an arbitrary number of RF tags 2 are attached to the vehicle 1 as necessary.
When the RF tag 2 receives a radio wave transmitted from the antenna 4, the RF tag 2 transmits a tag ID using the received radio wave as a power source.

The portable device 3 includes a receiving circuit (described later) for receiving a tag ID from the RF tag 2 and a transmitting circuit (not shown) for transmitting the received tag ID, and a plurality of RF tags When the tag ID transmitted by at least one of the two is received, the received tag ID is demodulated and transmitted.
The vehicle-mounted device 5 transmits a radio wave to the surroundings via an antenna 4 provided in the approximate center of the vehicle 1 and receives a tag ID from the portable device 3 to determine an area where the portable device 3 exists.

Here, as shown in FIG. 2, the antenna 4 connected to the vehicle-mounted device 5 includes a first unmodulated wave, a question signal following the first unmodulated wave, and a second unmodulated wave following the question signal. Transmit radio waves including.
In FIG. 2, the first unmodulated wave activates all the RF tags 2 attached to the vehicle 1. The question signal designates an arbitrary RF tag 2 among all the RF tags 2.
When the RF tag 2 receives the radio wave shown in FIG. 2 and is specified by the interrogation signal, the RF tag 2 superimposes the tag ID as a response signal on the second unmodulated wave following the interrogation signal. The radio wave shown in is sent.

  Further, the portable device 3 includes a radio wave intensity detecting means (described later) for detecting the radio wave intensity of the radio wave transmitted from the vehicle-mounted device 5 via the antenna 4, and based on the detected radio wave intensity, from the RF tag 2. The timing for starting the demodulation (reception processing) of the tag ID is determined.

The frequency characteristic of the RF tag 2 is suitable near 900 MHz or around 2.45 GHz, but is not necessarily limited to these frequencies, and may be any frequency in the high frequency band.
The antenna 4 and the vehicle-mounted device 5 are designed according to the frequency characteristics of the RF tag 2.

FIG. 4 is a block diagram showing a receiving circuit of portable device 3 according to Embodiment 1 of the present invention.
In FIG. 4, the receiving circuit includes an antenna 6, a coupler 7, a distributor 8, an amplifier circuit 9, a mixer 10, an amplifier circuit 11, a comparator 12, a signal processor 13, a detector 14, Comparator 15 is included.
Here, the distributor 8, the amplifier circuit 9, the mixer 10, the amplifier circuit 11, and the comparator 12 constitute a detection circuit 16 that detects a signal including the tag ID transmitted from the RF tag 2. The detector 14 and the comparator 15 constitute a radio wave intensity detection circuit 17 (radio wave intensity detection means) that detects the radio wave intensity of the radio wave from the vehicle-mounted device 5.
The signal processing unit 13 is configured by a microprocessor (not shown) having a CPU and a memory storing a program.

  The antenna 6 receives a radio wave transmitted from the vehicle-mounted device 5 (see FIG. 2) and a radio wave transmitted from the RF tag 2 (see FIG. 3) as reception signals. The coupler 7 distributes the reception signal received by the antenna 6, outputs one to the distributor 8, and outputs the other to the detector 14. The distributor 8 further distributes the signal distributed by the coupler 7, outputs one to the amplifier circuit 9, and outputs the other to the mixer 10. The amplifier circuit 9 amplifies the input signal and outputs it to the mixer 10 as a detection reference signal.

  Based on the signal output from the distributor 8 and the detection reference signal output from the amplifier circuit 9, the mixer 10 detects the signal including the tag ID by the self-homodyne detection method and outputs the signal to the amplifier circuit 11. . The amplifying circuit 11 amplifies the signal including the tag ID detected by the mixer 10 and outputs the amplified signal to the comparator 12. The comparator 12 binarizes the amplified signal and outputs the binarized signal to the signal processing unit 13.

The detector 14 outputs a voltage to the comparator 15 according to the radio wave intensity of the first unmodulated wave of the input signal (radio wave transmitted from the vehicle-mounted device 5). The comparator 15 binarizes the voltage output from the detector 14 on the basis of a predetermined voltage (radio wave intensity) that is arbitrarily set, and outputs it to the signal processing unit 13 as a reception start signal.
Here, the reception start signal becomes active when the voltage output from the detector 14 is larger than the predetermined voltage.

When the reception start signal is in an active state based on the signal including the tag ID binarized by the comparator 12 and the reception start signal output from the comparator 15, the signal processing unit 13 The tag ID is demodulated from the signal including, and the process proceeds to transmission processing by the transmission circuit.
That is, the portable device 3 determines the timing when the RF tag 2 transmits the tag ID by determining whether or not the reception start signal is in an active state, and demodulates the tag ID from the RF tag 2 (reception processing). ).

The operation of the signal processing unit 13 according to the first embodiment of the present invention will be described below with reference to the flowchart of FIG. 5 together with FIGS.
First, the signal processing unit 13 determines whether or not the reception start signal output from the comparator 15 is in an active state (step S21).
If it is determined in step S21 that the reception start signal is not in an active state (that is, No), the process immediately proceeds to step S21.

On the other hand, if it is determined in step S21 that the reception start signal is in an active state (that is, Yes), demodulation of the tag ID is started (step S22), and whether or not the tag ID has been correctly demodulated. Determination is made (step S23).
If it is determined in step S23 that the tag ID has not been correctly demodulated (that is, No), the process immediately proceeds to step S21.

  On the other hand, if it is determined in step S23 that the tag ID has been correctly demodulated (that is, Yes), the process proceeds to the transmission process by the transmission circuit (step S24), and the process of FIG.

Here, referring to FIG. 6, the signal processing unit 13 can demodulate the tag ID from the RF tag 2 with high accuracy compared to the case where the reception start signal is not input and the case where the reception start signal is not input. explain.
Inside the signal processing unit 13, a reference clock signal (demodulation reference clock) for demodulating the tag ID is generated, and this reference clock signal has a cycle so as to match the preamble signal included in the received signal. It is changed and an extra pulse is generated.

Here, when the reception start signal is not input, the cycle of the reference clock signal is always changed according to the reception signal. For this reason, the period of the reference clock signal is also changed by an erroneous received signal due to noise or the like.
On the other hand, when the reception start signal is input, the start position of the preamble signal included in the reception signal can be detected in advance according to the state of the reception start signal. Therefore, the period of the reference clock signal starts to change when the reception start signal becomes active, and the period becomes difficult to change.
Therefore, the tag ID from the RF tag 2 demodulated with this reference clock signal is demodulated with high accuracy.

According to the vehicle communication device according to the first embodiment of the present invention, the portable device 3 receives the reception start signal based on the reception start signal output according to the radio wave intensity transmitted from the vehicle-mounted device 5. In the active state, the demodulation (reception processing) of the tag ID from the RF tag 2 is started.
Therefore, even when the vehicle-mounted device 5 and the portable device 3 are separated, the preamble signal can be accurately detected and the tag ID from the RF tag 2 can be demodulated with high accuracy.

Embodiment 2. FIG.
In Embodiment 1 described above, radio wave irregular reflection occurs in the vehicle 1 that is an enclosed space, and there are places where the radio field intensity is high and areas where the radio field intensity is low. Always changes, and the tag ID from the RF tag 2 cannot be received stably.
Therefore, it is desirable to adjust the gain of the amplifier circuit 9 so as to keep the reception sensitivity of the portable device 3 constant according to the intensity of the radio wave transmitted from the vehicle-mounted device 5.

FIG. 7 is a block diagram showing a receiving circuit of portable device 3 according to Embodiment 2 of the present invention.
In FIG. 7, the reception circuit includes a reception signal level adjustment circuit 18 (reception signal level adjustment means) that adjusts the reception signal level of the tag ID from the RF tag 2.
The reception signal level adjustment circuit 18 includes a detector 14 and an amplifier circuit 9A, and the output of the detector 14 is input to the amplifier circuit 9A.

The amplifier circuit 9A changes the gain according to the voltage output from the detector 14, amplifies the signal output from the distributor 8 with this gain, and adjusts the received signal level within an arbitrary predetermined range. It outputs to the mixer 10 as a detection reference signal.
The mixer 10 can detect the signal including the tag ID in the region having the same sensitivity point by using the detection reference signal output from the amplifier circuit 9A.
Other configurations and operations are the same as those in the first embodiment, and a description thereof will be omitted.

According to the vehicle communication device of the second embodiment of the present invention, the received signal level adjusting means changes the gain of the amplifier circuit 9A according to the voltage output from the detector 14, and the amplifier circuit 9A Based on the above, a detection reference signal for adjusting the received signal level within an arbitrary predetermined range is output to the mixer 10.
Therefore, the tag ID from the RF tag 2 can be stably received, and the tag ID from the RF tag 2 can be demodulated with higher accuracy.

It is a block diagram which shows the vehicle carrying the vehicle communication apparatus which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the electromagnetic wave transmitted from the antenna connected to the onboard equipment which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the electromagnetic wave containing tag ID transmitted from RF tag which concerns on Embodiment 1 of this invention. It is a block diagram which shows the receiver circuit of the portable device which concerns on Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the signal processing part which concerns on Embodiment 1 of this invention. It is explanatory drawing explaining that the tag ID from RF tag can be demodulated with high precision in the signal processing part which concerns on Embodiment 1 of this invention. It is a block diagram which shows the receiving circuit of the portable device which concerns on Embodiment 2 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Vehicle, 2 RF tag, 3 portable machine, 4 antenna, 5 onboard equipment, 17 radio wave intensity detection circuit (radio wave intensity detection means), 18 reception signal level adjustment circuit (reception signal level adjustment means).

Claims (2)

A plurality of RF tags attached to a plurality of locations of the vehicle, each having a unique tag ID;
A portable device carried by a user of the vehicle;
An in-vehicle device provided in the vehicle and connected to an antenna for transmitting and receiving radio waves;
Each of the plurality of RF tags, when receiving the radio wave transmitted from the antenna, transmits the tag ID using the radio wave as a power source,
When the portable device receives the tag ID from the RF tag, the portable device transmits the received tag ID,
The vehicle-mounted device is a vehicle communication device that transmits the radio wave via the antenna, receives a tag ID from the portable device, and determines a region where the portable device exists,
The portable device includes a radio wave intensity detecting unit that detects a radio wave intensity of the radio wave from the vehicle-mounted device, and determines a timing for starting reception processing of a tag ID from the RF tag based on the radio wave intensity. A vehicle communication device.   The portable device includes a received signal level adjusting unit that adjusts a received signal level of the tag ID from the RF tag, and the received signal level adjusting unit keeps the received signal level within a predetermined range according to the radio wave intensity. The vehicle communication device according to claim 1, wherein the vehicle communication device is adjusted.

Images