JPH0382979A - Apparatus for discriminating movable body - Google Patents

Abstract

PURPOSE:To prevent jamming and erroneous transmission or the generation of noise to some other place by transmitting an auxiliary carrier wave of frequency lower than that of a carrier wave from an interrogator and prohibiting a responder entrance signal in the presence of a communication signal at the start time of the operation of the power supply of a responder. CONSTITUTION:When an ID card (responder) 400 enters an communication region at first, the card receives the non-modulated carrier wave of an interrogator 300 and the power supply of the interrogator 300 begins to operate and the carrier wave is modulated by a modulator 410 to send a responder entrance signal. The interrogator 300 generates an auxiliary carrier wave having frequency lower than that of the carrier wave and higher than signal frequency in place of the carrier wave to transmit the same. Further, the modulated carrier wave and the auxiliary carrier wave are received and demodulated to obtain the responder entrance signal and a discrimination signal. The card 400 receives the auxiliary carrier wave to modulate the same to return the discrimination signal and receives a frequency component equal to or less than the frequency of the auxiliary carrier wave to generate a communication signal and, at the start time of the operation of the power supply 405, the return of the responder entrance signal is prohibited by the monitoring of a high band component detector 406 when the communication signal is present.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a mobile object identification device, and particularly to preventing interference therein.

[Prior Art] In recent years, attempts have been made to attach D (identification) cards to moving objects such as containers, automobiles, and human bodies to perform logistics management, fee collection, gate management, etc. ID cards are used as small and lightweight transceivers (transponders) that respond with identification codes in response to interrogation radio waves from a central transceiver (interrogator), and devices that identify mobile objects without contact are attracting attention. There is.

An example thereof will be explained below with reference to FIGS. 7 and 8.

The carrier wave output from the high frequency oscillator ↓01 (hereinafter referred to as an oscillator) of the interrogator ↓00 is sent to a branch 102', a modulator 103,
The signal is transmitted from the antenna 105 via the circulator]-04. When the interrogator 100 is on standby, that is, when it is waiting for the arrival of the ID card 200 to be sold, the modulation input 1a of the interrogator 100 is nQ as shown in FIG.
The Nn state is maintained and unmodulated high frequency waves continue to be transmitted from the antenna 105.

When the ID card 200 enters the detection area of the interrogator 100, the unmodulated high frequency wave is received by the antenna 20 of the ID card 200 through the route shown in FIG. The high frequency detector 202 detects the wave, and the amplifier 20
3, the peak detector 204 and the waveform shaper 2
The output 2b of the peak detector 204 is input to the power supply 205, and the output 2b of the peak detector 204 is input to the power supply 205,
Power is supplied to the CPU 207 of the D card 200 (7th
(dotted line in the figure), the CPU 207 starts operating.

On the other hand, the unmodulated high frequency wave from the interrogator 100 is simultaneously received by the antenna 211 of the ID card 200 from the IC path. Then, the CPU 207 of the ID card 200
After loading your own ID card from the memory 208 and converting it into a modulated signal, output the signal 2C), the terminal resistor 21.
The unmodulated wave received by the antenna 211 is ASK-modulated by the reflection modulator 20 with the antenna 0 connected to one end, and the antenna 211 sends it back again as shown in FIG. 8 (5>E>).

This returned modulated wave is transmitted to the interrogator 1 via the path 2d.
00 antenna ↓ Received by 05, circulator 10
4 to the mixer 106. This mixer 1
The unmodulated high frequency wave outputted from the branch 1°02 is inputted to 06 as a local oscillation signal, and the mixer 106 performs mixed square law detection (homodyne detection) on the received wave and the local oscillation signal. A signal based on the modulated signal 2C is output. The signal 1d is then passed through an amplifier 107 and a waveform shaper 108 to a post computer (not shown).
is output to.

The host combination 1-1 reads the ID code of the ID card 200, and then outputs a write signal 1a as a modulation signal in order to write predetermined data to the ID card 200. Then, the unmodulated high frequency wave from the oscillator 101 is ASK modulated.
The detected write signal is input to the high frequency detector 202 via the amplifier 203 and the waveform shaper 206 (signal 2e), and is input to the CPU 207 (signal 2e).
8 is stored. After that, the CPU 207 stops its read/write operation, but depending on the case, it may output a signal to the modulator 209 to notify the end of writing and send a confirmation signal to the interrogator 100.

During this time, the output of the peak detector 204 of the ID card continues to hold the ON horn (from C) in FIG. 0 point in Figure 8 (4)> and # OF
F/7, and the ID card 200 is about to stop its operation. While this series of operations is progressing on the first ID card, when the second ID card enters, the second ID card starts operating. Initially, malfunctions such as being unable to read or write occur.

Therefore, in order to solve this problem, for example,
- In Publication No. 134978, prior to a data request signal (interrogation signal) to the transponder, the interrogator emits a preliminary signal in the form of a pulse at a constant period, and priority is given to the transponder that has received and replied this preliminary signal. A device that communicates with each other has been proposed.

[Problem B to be Solved by the Invention] However, in the conventional device described above, since the preliminary signals are emitted at intervals, a plurality of transponders enter the communication area between the preceding and following preliminary signals, and both A problem arises in that the signals respond to prior signals and cause interference. In order to reduce this probability, it is necessary to shorten the pulse interval of the prior signal, but if this pulse interval is reduced to the pulse period of the write signal from the interrogator, a false belief with the write signal will occur, and this Since the pre-signal is constantly emitted, there is a risk that it may cause counterfeit noise to be generated in other electronics devices surrounding the identification device that use the same frequency band.

The present invention solves these problems and provides a mobile object identification device that can effectively prevent interference caused by a plurality of transponders that have entered a communication area, and that is free from the possibility of misrepresentation of written signals or generation of noise. purpose.

[Means for Solving the Problems] The configuration of the present invention will be explained with reference to FIG. 1. In a mobile object identification device that performs identification communication between an interrogator provided on a fixed side and a transponder provided on a mobile object, The interrogator includes a carrier wave generating means that continuously generates an unmodulated carrier wave, and a subcarrier having a frequency lower than the carrier wave frequency and higher than the signal frequency, in place of the above carrier wave when the transponder entry signal is received. a subcarrier generating means for generating a subcarrier, a transmitting means for transmitting the carrier or subcarrier, and a demodulating means for receiving and demodulating the modulated carrier or subcarrier to obtain the transponder entry signal or identification signal. On the other hand, the transponder is equipped with a power supply that operates when receiving the carrier wave or subcarrier wave, an approach signal reply means for modulating the received carrier wave and returning the transponder approach signal, and a receiving signal. identification signal return means that modulates the subcarrier and returns the identification signal; communication signal generation means that generates a communication signal when a frequency component lower than the frequency of the subcarrier is received; If a communication signal exists, a reply prohibition means is provided for prohibiting reply of the transponder entry signal.

[Operation] In the mobile object identification device having the above configuration, when the first transponder enters the communication area, the transponder's power supply starts operating upon receiving the unmodulated carrier wave from the interrogator, and the entry signal reply means A transponder entry signal is returned from the transponder.

When the subcarrier generation means of the interrogator receives the transponder entry signal, it generates a subcarrier in place of the carrier wave, and the identification signal return means of the transponder modulates the received subcarrier to generate an identification signal. Reply.

Even if the next transponder enters the communication area during this time, the subcarrier is still being transmitted from the interrogator, so the reply prohibition means is activated and the transponder entry signal is prohibited from being returned, and the communication state is maintained. doesn't fit.

In such operation, the first transponder that enters the communication area receives the interrogator's unmodulated carrier and returns a transponder entry signal; in response, the interrogator emits a subcarrier; Since the time from the reply of the transponder entry signal to the transmission of the subcarrier can be set sufficiently short,
During this time, the probability that the next transponder will enter the communication area is extremely small.

Since the unmodulated carrier wave mentioned above is continuous, when the first transponder enters the communication area, a transponder entry signal is immediately emitted and subcarrier transmission begins, and the next transponder follows at a short time interval. Transponder communication is reliably prohibited.

In addition, since the carrier wave is unmodulated, even if it is emitted all the time, it can be avoided from being mistaken for a write signal, and it will not cause any adverse effects such as noise on other devices.

[Example] In FIG. 2, 300 is an interrogator that transmits and receives high-frequency radio waves to read and write to a transponder (ID card) attached to a mobile object, and 400 is an interrogator that reads and writes to a transponder (ID card) attached to a mobile object. It is a possible ID card.

In the interrogator 300, 301 is an oscillator that generates an unmodulated carrier wave for transmission and reception. 302 is a branch that distributes high frequency waves in two directions at a predetermined power ratio. 303 is composed of a PIN diode, etc., and electrically transmits high frequency)
A modulator that performs ASK modulation by performing n Q F F //. 304 is a circulator that controls a high frequency transmission path. 305 is an antenna that transmits and receives high frequency radio waves. 30
6 is composed of a Schottky barrier diode, etc., and 2
It is a mixer that performs mixed power detection using human power, and in this embodiment, it works as a homodyne detector. An amplifier 307 receives the output of the mixer 306 and amplifies only the amplitude modulation component of the received wave. 3
08 is an envelope detector that detects only the subcarrier-0 transmission component of the amplified amplitude modulation component. 309 is a waveform shaper that shapes the output of the envelope detector 308 into a digital signal.

In the ID card 400, a reception-only antenna 401 receives the unmodulated wave for operation and the high frequency wave for writing from the interrogator 300. 402 is a carrier wave detector that detects a high frequency component and outputs its envelope.

403 is an amplifier that amplifies the output of the direct detector 402;

404 is a peak detector that detects and holds the peak value of the amplified envelope. 405 is a power supply that receives the output of the peak detector 404 and supplies the power supply voltage through the dotted line path in the figure when in the tt ON n state. 406 is a high-frequency component detector that passes the frequency component of the write ASK signal and the frequency component of the subcarrier out of the envelope output from the amplifier 403, and outputs a J*N horn when the frequency component exists. .

407 is a waveform shaper that shapes the output of the amplifier 403 into a digital signal. 408 is activated by the output of the power supply 405 (dotted line in the figure), outputs a readout 1 final modulation signal at the timing when the output of the high frequency component detector 406 is generated, and inputs the output of the waveform shaper 407 as a write signal. The CPU 0409, which is programmed with a predetermined processing routine, is connected to the CPU 408, holds data for reading, and executes the CPU 0409 when reading data.
A memory that outputs data to the PU 408 and inputs and holds write data from the CPU 408 during writing.
It has a function that retains its contents even when it is stopped.

Reference numeral 410 denotes a modulator having the same configuration as the modulator 303, and by terminating one terminal with a terminating resistor 411, reflective ASK modulation is realized. In other words, modulation input n ON
When n, the received high frequency is absorbed by the terminating resistor 411,
ASK modulation is performed by not reflecting, but reflecting at the time of modulation (QF F n). 411 is a terminating resistor equal to the characteristic impedance of the line. 412 is a transmitting and receiving antenna.

The operation of such a mobile object identification device will be explained with reference to FIGS. 3 to 7.

An unmodulated carrier wave generated by an oscillator 301 of an interrogator 300 is transmitted from an antenna via a branch 302, a modulator 303, and a circulator 304. Interrogator 3
00 standby, that is, ID card 40 to be read and written
When waiting for the arrival of 0, the modulator 3 of the interrogator 300
The modulation input 3a of 03 is I as shown in A of Fig. 3 (1).
The t ON // state is maintained, and the unmodulated carrier wave continues to be transmitted from the antenna 305 (D in FIG. 3 (2)). When the ID card 400 enters the detection area (not shown) of the interrogator 300, the unmodulated carrier wave is transmitted to the ID card 40 from the path 3B in FIG.
0 antenna 401, detected by high frequency detector 402, and then amplified by amplifier 403 (signal 4a)
. The output of amplifier 403 is input to peak detector 404 . The peak detector 404 outputs J) ON n to the power supply 405 for operating the CPU 0409 (H) in FIG. Start up.

On the other hand, the unmodulated wave from the interrogator 300 is simultaneously received by the anti-3 screen 412 of the ID card 400 via the 3C path. After startup, the CPU 408 of the ID card 400 sends the ID to the interrogator 300.
In order to notify that the card 400 is entering, a predetermined code (in this embodiment, three pulses, J in FIG. 3(5)) is output to the modulator 410. Modulator 410 receives this modulation signal, performs ASK modulation on the carrier wave received by antenna 412, and sends it back again (L in FIG. 3 (6)). This modulated carrier wave is route 4
The signal is input to the mixer 306 via the antenna 305 of the interrogator 300 and the circulator 304 via d. This mixer 306 is always outputted from the branch 302. The unmodulated carrier wave is input as a local oscillation signal, and the mixer 306 performs mixed square detection of the received wave and the local oscillation signal, and outputs an I
A signal based on the modulated signal 4C of the D card 400 is output. The signal is then input to a detector 308 via an amplifier 307. The detector 308 performs envelope detection of a subcarrier (described later), which is a frequency component sufficiently faster than the baud rate indicating the data transmission speed (for example, at a transmission speed of 49,600 baud, the subcarrier is several hundred KHz). shall be set>, the amplified signal is transmitted to the detector 30
8 and is outputted to the host computer via the waveform shaper (N in FIG. 3 (8)).

The host computer detects the entry of the ID card 400 and sends a subcarrier (digital AM without information) to the modulator 303 of the interrogator 300 in order to read the ID code held by the ID card 400. The frequency of this subcarrier is set to be sufficiently faster than the data transmission speed frequency that defines the baud rate, but sufficiently lower than the non-modulated carrier. Chopper modulation for generating subcarriers can be easily realized (for example, for a data transmission rate of 9600 baud, the subcarriers are several hundred KH2 and the number of unmodulated carriers is GHz).

The subcarrier is transmitted to the antenna 3 via the circulator 304.
05 (E in Figure 3 (2)). Its enlarged view is shown in Figure 4. This transmitted sub-5 carrier wave is input from channel #13b, and while maintaining the peak detection output. , on the other hand, is input to the modulator 4 of the ID card 400 from the path 3C.

The CPU 408 of the ID card 400 loads its own code from the memory 409, converts it into a modulation signal, and then modulates it (K in Fig. 3 <5>).

The subcarrier is received by the interrogator 300 via the ff84d, inputted to the mixer 306 via the circulator 304, and the modulated signal component is amplified and inputted to the detector 308 (M in Fig. 3 (7)). The detector 308 performs envelope detection on the subcarrier, shapes the waveform, and outputs it to the host computer (P in FIG. 3 (8)).

The host computer reads the ID code of the ID card 400, and then sends the interrogator 3 to write predetermined data.
A modulated signal is output to the modulator 303 of 00 (the third
Figure (1>C>) The modulated carrier wave is received by the 40 antennas of the ID card 400 via the path 3b, and transmitted to the CP via the detector 402, amplifier 403, and waveform shaper 407.
The write data is input to U408 and stored in memory 409. After this, the ID card 400 enters an unprocessed state and eventually leaves the communication area with the interrogator (G in FIG. 3 (3)).

A case in which another ID card enters during such a series of operations will be described below.

In addition to the peak detector 404 and waveform shaper 407, the output of the amplifier 403 of the ID card 400 is input to a high frequency component detector 406.
6 is n Q N n only when receiving the signal 4e (as shown in FIG. When input and activated, this signal 4
e is monitored, and at the same time when 4e becomes )l ON //, it is determined that another ID card is already in operation, its operation is postponed, and then it is activated after 4e becomes JJ OFFn state. Take the step of starting.

The processing procedure for the ID card 400 is shown in FIG.
FIG. 6 shows the processing procedure of the host computer connected to the computer.

7 That is, the first ID card receives signal 4b (Fig.
After being activated at the rising edge of >, it is determined in steps 41 and 42 whether 4b-horn ON//and 4e-〃FF〃. The fact that this condition is met also indicates that the second ID card is not operating, and the first ID card executes steps 43 to 47 and ends the process. The interrogator host computer has an ID card 30.
Steps 31 to 33 are repeated during the entry standby of 0, and when the first ID card enters, step 33 becomes ``YES'', and resteps 34 to 37 are executed, and the process returns to the standby state.

Here, the first ID card is recognized by the interrogator's host computer and the second ID card is recognized by the interrogator's host computer while performing steps 34-37.
When the ID card enters, step 42 of the second ID card does not hold, and the second ID card enters step 43.
The user waits for the first ID card to complete.

Moreover, the 4cmJ signal that conveys the presence of an ID card to the interrogator's host computer is common to all ID cards, making recognition possible in an extremely short time.
Interference and malfunction caused by the D card can be prevented.

In addition, in the second embodiment, A of the ID card 400,
Even if the SK modulator is replaced with a PSK modulator, the other configurations remain the same and the same effect can be obtained.

[Effects of the Invention] As described above, according to the mobile object identification device of the present invention, it is possible to reliably prevent interference from a plurality of transponders entering the communication area with an interrogator at short time intervals. At the same time, the problem of erroneous belief with a write signal or noise interference with other equipment does not occur when the intrusion detection accuracy is increased, as in the prior art.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to the claims of the present invention, Figs. 2 to 6 show an embodiment of the present invention, Fig. 2 is an overall block diagram of the device, and Figs. 3 and 4 are signal time charts. ,
5 and 6 are flowcharts showing the processing procedures of the ID card and interrogator, respectively, FIGS. 7 and 8 show a conventional example, FIG. 7 is an overall block diagram of the device, and FIG. Time chart 1-. 300... Interrogator 30↓... Oscillator 303... Modulator 305... Antenna 306... Mixer 308... Envelope detector 400... ID cart (responder) 401... Antenna 402...High frequency detector 404...Peak detector 405...Power source 406...High frequency component detector 408...CPU 409...Memory 410...Modulator 4 upper 2...・Antenna Fig. 8 Fig. 8 Interrogation ship response ping Fig. 2 4'OO Fig. 5 Fig. 6 Fig. 7 1b ■ 00

Claims (1)

[Claims] In a mobile object identification device that performs identification communication between an interrogator provided on a fixed side and a transponder provided on a mobile object, the interrogator includes a carrier wave generating means that continuously generates an unmodulated carrier wave; subcarrier generating means for generating a subcarrier with a frequency lower than the frequency of the carrier wave and higher than the signal frequency in place of the carrier wave when a transponder entry signal is received; and a transmitting means for transmitting the carrier wave or subcarrier wave; demodulation means for receiving and demodulating the modulated carrier wave or subcarrier wave to obtain the transponder entry signal or identification signal; an operating power supply; an ingress signal return means for modulating the received carrier wave and returning the transponder approach signal; an identification signal return means for modulating the received subcarrier wave and returning the identification signal; communication signal generation means for generating a communication signal when a frequency component lower than the frequency of the carrier wave is received; and reply prohibition means for prohibiting reply of the transponder entry signal when the communication signal is present when the power source starts operating. A mobile object identification device comprising: