JP3190572B2 - Communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication apparatus which does not cause interference even if a plurality of transponders are adjacent to each other and is suitable for identification of a moving body.

[0002]

2. Description of the Related Art If an individual identification code of a passing car can be instantaneously read at a tollgate on a toll road, it is not necessary to stop the car at the tollgate by adjusting the toll at a later date. Can be eliminated. Therefore, various communication devices have been proposed for communicating an individual identification code of a vehicle between an interrogator provided on each lane of a tollgate and a transponder mounted on the vehicle. As an example, see Japanese Patent Application Laid-Open No. 6-1.
There is one disclosed in Japanese Patent No. 81449. The following is a brief description of this technique. First,
The interrogator has a plurality of time-division channels and transmits channel information indicating the presence or absence of an empty channel for each channel to a transponder mounted on the vehicle. The transponder selects any empty channel and returns the vehicle's unique identification code. The interrogator receives the returned signal, and when there is a collision (interference) in which a plurality of transponders select the same channel, the interrogator transmits the channel information again with the channel being an empty channel. The transponder confirms that the selected channel does not transmit channel information again as an empty channel and determines that there is no interference. When the channel information of the empty channel is transmitted again from the selected channel, an arbitrary empty channel is selected again, and the unique identification code is returned again. The transponder repeats the return until the selected channel is no longer transmitted as channel information and the channel information is not transmitted again. In such a conventional technique, there is no possibility of interference even if a plurality of transponders exist.

In addition, interference is prevented due to the presence of a transponder in an adjacent lane by allocating time-division channels to interrogators provided in each lane and shifting communication times in each lane. There is technology to do.

[0004]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Laid-Open No. 6-18 / 1994
The conventional technique disclosed in Japanese Patent No. 1449 is excellent in that no interference occurs. However, whether or not the transponder selects an empty channel that does not collide is a matter of chance.If, unfortunately, multiple transponders select the same channel one after another, it will take longer for reliable communication to occur. It may take a long time. In other words, the time required for reliable communication varies. Therefore, in order to be able to cope with a case where a long time is required for communication, for example, the transmitting and receiving antenna on the interrogator side is moved in one direction in the lane.
Instead of being provided at a point, there is a demand for a technique of providing the device long along the traveling direction of the vehicle. On the other hand, the number of transponders existing in the range increases as the transmission / reception antenna becomes longer and the communication time increases, and the possibility of collision in the channel increases accordingly.

[0005] In the technique of distributing each time-divided channel to the interrogator provided in each lane, the communicable time in each lane is short, and it is not suitable for transmitting and receiving a large amount of data. .

Therefore, the prior art is not suitable as a device for communicating a large amount of data during a short time when a car passes at high speed under an interrogator provided in each lane of a toll road. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned disadvantages of the related art, and enables an interrogator to control the frequency of a response carrier of a transponder so as to prevent interference between adjacent transponders. It is an object of the present invention to provide a communication device having the above configuration.

[0008]

In order to achieve the above object, a communication apparatus according to the present invention uses a plurality of interrogators to transmit modulated signals obtained by modulating interrogated carrier waves with different reference frequencies, respectively, to corresponding transponders. Send to
Each of the transponders receives the modulated signal, demodulates the reference frequency, generates a response carrier by a response carrier means comprising a PLL circuit using the reference frequency as a reference signal, and responds to the interrogator corresponding to the response carrier. The interrogator that transmits to the receiver and receives the response carrier is configured such that no interference occurs due to the difference in the frequency of the response carrier between the corresponding transponder and the other transponder.

The response carrier oscillating means for oscillating the response carrier may be turned on / off according to the presence or absence of the demodulation reference frequency.

A plurality of interrogators are provided corresponding to a plurality of lanes, respectively. An interrogator transmitting antenna for transmitting a modulated signal obtained by modulating the interrogation carrier at the reference frequency transmits a beam to the corresponding lane. The transponder may have directivity to irradiate, and the transponder may be arranged on a moving body passing through the lane.

Furthermore, a plurality of the interrogators are arranged in each lane at a tollgate on a toll road, and the transponder is mounted on a car and transmits the response carrier wave oscillated using the demodulated reference frequency as a reference signal. It may be configured to transmit a modulated signal modulated with the vehicle unique identification code to the corresponding interrogator.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will now be described with reference to FIG.
This will be described with reference to FIGS. FIG. 1 is a block circuit diagram of a communication device according to an embodiment of the present invention. FIG. 2 is a diagram in which the communication device of FIG. 1 is applied to a tollgate on a toll road. FIG.
FIG. 3 is a diagram showing an example of setting of a carrier (a) and a reference frequency (b) in each lane of FIG. 2.

In FIG. 1, the interrogator 10 has a query carrier oscillating means comprising a VCO 12 and a PLL 14 for oscillating a query carrier, and a reference frequency oscillating means comprising another VCO 16 and a PLL 18 for oscillating a reference frequency. Then, the reference frequency and the transmission data are selected by the switch 20, and one of the selected signals is given to the modulator 22. Also, this modulator 22
Is also modulated with the selected signal, and the interrogated modulated signal is transmitted from the interrogating transmitting antenna 26 via the power amplifier 24 to the transponder 5.
Sent toward zero.

Further, the response carrier transmitted from the transponder 50 is received by the interrogating receiving antenna 28,
To the mixer 32. The interrogator 32 is also provided with the interrogation carrier, and the mixed output is applied to the demodulator 34 to demodulate and output the received data.

The transponder 50 receives the interrogating carrier at the receiving antenna 52 on the response side and rectifies the interrogated carrier at the rectifier 54. The rectified signal is output as received data via the amplifiers 56 and 58.

A reference frequency is extracted and demodulated from the output of the amplifier 56 by a band-pass filter 60, and the demodulated reference frequency is provided to a phase comparator 62 and a second rectifier 64. The phase comparator 62 receives the frequency-divided output from the frequency divider 66, a signal corresponding to the phase difference between the demodulation reference frequency and the frequency-divided output is supplied to the low-pass filter 68, and the output is supplied to the VCO 70. . The oscillation frequency output from the VCO 70 is a response carrier wave, and is provided to the frequency divider 66 and the modulator 72. The modulator 72 is provided with transmission data on the transponder 50 side, and a response modulation signal obtained by modulating a response carrier with the transmission data is transmitted from the responding transmission antenna 74 to the interrogator 10. Then, the output of the rectifier 64 is given to a smoothing circuit 76, and the DC output signal is
As an ON / OFF control signal.

The operation of the above configuration will be described below. First, for example, the interrogator 10 has a query carrier of 5.800 GHz and a reference frequency of 1.800 GHz.
000 MHz and transmission data rate is 2.0MPP
S. At the time of data transmission, the switch 20 selects transmission data and sends 5.800 G from the interrogation-side transmission antenna 26.
A modulated signal obtained by ASK-modulating the interrogated carrier of the Hz with the transmission data is transmitted to the transponder 50.

Then, the transponder 50 receives the modulated signal, the received data is demodulated by the rectifier 54, and is appropriately amplified via the amplifiers 56 and 58 and output as the received data. Here, the band-pass filter 60 has a characteristic of passing both the reference frequency and the transmission data on the interrogator 10 side. However, the transponder 50 does not receive the transmission data on the transponder 50 side to the modulator 72 because of the sequence based on the received data.

Next, when the transmission of the transmission data from the interrogator 10 is completed, the switch 20 is switched to select a reference frequency.
A modulated signal in which the interrogation carrier is ASK-modulated at the reference frequency is transmitted to the transponder 50. Then, the transponder receives this modulated signal, but the reference frequency output from rectifier 54 has no meaning as received data. However, the reference frequency passes through the band-pass filter 60 and is provided to the phase comparator 62 and the second rectifier 64. The output of the second rectifier 64 is converted to a DC output signal by the smoothing circuit 76, and the control signal is V
The CO 70 is set to the operating state. Then, the response carrier oscillating means is activated, and the response carrier is oscillated and output. If the frequency division ratio of the frequency divider 66 is, for example, 1/5850,
The response carrier is 5.850 GHz. This response carrier is transmitted to the modulator 72 by the transmission data on the
The signal is modulated and transmitted from the response-side transmission antenna 74 to the interrogator 10. Note that the second rectifier 64 and the smoothing circuit 76 may be omitted, and the VCO 70 may always be operating.

Then, the interrogator 10 receives this modulated signal at the interrogating-side receiving antenna 28, and the received signal is
The signal is amplified by 0 and supplied to the mixer 32. This mixer 3
In 2, the signal is mixed with the interrogation carrier of 5.800 GHz, and a signal superimposed on the difference frequency of 50 MHz is output from the demodulator as reception data.

Next, a description will be given, with reference to FIGS. 2 and 3, of a case where the communication device shown in FIG. 1 is applied to a tollgate on a toll road.

In FIG. 2, as an example, the tollgate has a first lane to a third lane, and interrogators 10-1, 10-2, and 10-3 are respectively provided above the lanes. In addition, the transponders 50-1 and 50-1
50-2 and 50-3 are respectively mounted. Further, in the interrogator 10-1 provided in the first lane, 5.800 GHz is set as the interrogation carrier and 1.00000000000 MHz is set as the reference frequency. The interrogator 10-2 provided in the second lane includes:
810 GHz and 1.001709402 MHz are set respectively. Further, the interrogator 10-3 provided in the third lane has 5.820 GHz and 1.0034188.
03 MHz is set respectively. The transponder 50-
1, 50-2 and 50-3 are the same, and the frequency division ratio of the frequency divider 66 is set to 1/5850. Then, the transponder 5 mounted on the car in the first lane 5
The response carrier of 0-1 is 5.850 GHz, and the response carrier of the transponder 50-2 mounted on the vehicle in the second lane is 5.860 GHz, and the transponder 50- mounted on the vehicle on the third lane. 3. The response carrier is 5.870 GHz
Becomes Therefore, the transponders 50-1, 50-2, 50
-3 outputs a response carrier of a different frequency depending on which lane the vehicle is in. And Interrogator 5
Since the interrogating-side transmitting antennas 26 provided at 0-1, 50-2, and 50-3 have directivities for irradiating a beam only to the relevant lane, a transponder mounted on a car in an adjacent lane is used. The reception electric field strength at 50 is much smaller than the reception electric field strength for the interrogator 50 of the lane, and is sufficiently suppressed. As a result, even if there are a plurality of interrogators 10 and transponders 50 in adjacent lanes, no interference occurs. In addition, communication can be secured instantaneously, and reliable communication can be ensured even when a vehicle travels and passes a tollgate.

In the above-described embodiment, the voltage controlled oscillation circuit is used for the interrogating carrier oscillation means and the reference frequency oscillation means of the interrogator 10, but it goes without saying that any oscillation circuit may be used. In the transponder 50,
The smoothing circuit 76 may output a DC output signal for ON / OFF control of the VCO 70, and may be a circuit having a large time constant such as a low-pass filter or a CR integrator.
The response carrier oscillating means turns on / off the VCO 70
It is not limited to the one that is activated / deactivated by the FF control, but may be any one that is controlled according to the presence or absence of the reference frequency. Further, the frequency of the interrogation carrier of the interrogator 10 may not be different for each lane.

[0024]

As is apparent from the above description, the communication apparatus of the present invention has the following special effects.

In the communication apparatus according to the first aspect, a plurality of interrogators transmit modulated signals obtained by modulating interrogated carrier waves with different reference frequencies, and the corresponding transponders use the reference frequency as a reference signal. Since the response carriers having different frequencies are transmitted, even if there are a plurality of transponders in the interrogator, no interference occurs between the corresponding transponder and the other transponders.

In the communication apparatus according to the second aspect, the transponder demodulates the reference frequency and, when its existence is confirmed, puts the response carrier oscillation means into an operating state. There is no unnecessary power consumption.

In the communication device according to the third aspect, since the reference frequency of each lane is different and the interrogating transmitting antenna has directivity for irradiating a beam to the corresponding lane, the transponders are adjacent to each other. Since the electric field strength from the lane is weak and sufficiently suppressed, and a response carrier having a different frequency is transmitted for each lane, no interference occurs with the interrogator and transponder in the adjacent lane.

Further, in the communication device according to the fourth aspect, the interrogator provided at the tollgate on the toll road and the transponder mounted on the car do not cause interference, and the communication is instantaneous. Since data can be secured, data can be sufficiently exchanged even when a car passes through a tollgate while traveling. Therefore,
Ideal for eliminating congestion at toll booths.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of an embodiment of a communication device according to the present invention.

FIG. 2 is a diagram in which the communication device of FIG. 1 is applied to a tollgate on a toll road.

3A is a diagram illustrating setting of a carrier wave in each lane, and FIG. 3B is a diagram illustrating setting of a reference frequency in each lane.

[Explanation of symbols]

 Reference Signs List 10 Interrogator 12, 16, 70 VCO 14, 18 PLL 20 Switch 22, 72 Modulator 24, 30, 56, 58 Amplifier 26 Interrogator transmitting antenna 28 Interrogator receiving antenna 32 Mixer 34 Demodulator 50 Transponder 52 Responder Receiving antennas 54, 64 Rectifier 60 Band-pass filter 62 Phase comparator 66 Divider 68 Low-pass filter 74 Response-side transmitting antenna 76 Smoothing circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-102349 (JP, A) JP-A-58-151132 (JP, A) JP-A-8-23291 (JP, A) JP-A 8- 36052 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04B 1/59 G01S 13/75-13/79 H04B ⁷ /24-7/26

Claims (4)

(57) [Claims] A plurality of interrogators transmit modulated signals obtained by modulating interrogated carrier waves at different reference frequencies to corresponding transponders, and the transponders receive the modulated signals respectively. The reference frequency is demodulated, a response carrier comprising a PLL circuit is used as a reference signal to generate a response carrier using the reference frequency as a reference signal, the response carrier is transmitted toward the corresponding interrogator, and the response carrier is received. A communication device, wherein an interrogator is configured such that interference does not occur due to a difference in the frequency of a response carrier between a corresponding transponder and another transponder. 2. The communication apparatus according to claim 1, wherein said response carrier oscillating means for oscillating said response carrier is ON / OFF controlled according to the presence or absence of said demodulation reference frequency. . 3. The communication device according to claim 1, wherein a plurality of said interrogators are respectively arranged in correspondence with a plurality of lanes, and transmit a modulated signal obtained by modulating said interrogation carrier at said reference frequency. A communication device, wherein the interrogating-side transmission antenna has directivity for irradiating a beam to a corresponding lane, and the transponder is arranged on a moving object passing through the lane. 4. The communication device according to claim 3, wherein a plurality of said interrogators are respectively arranged in each lane at a tollgate on a toll road, and said transponder is mounted on a car, and said interrogator is referenced to said demodulation reference frequency. A communication device, wherein a modulated signal obtained by modulating the response carrier oscillated as a signal with a unique identification code of the vehicle is transmitted to the corresponding interrogator.