JPH0644488A - Communication area detection circuit for non-contact ic card - Google Patents

Abstract

PURPOSE:To prevent the service span of life of a battery from becoming short due to the generation of an interruption to a CPU by the influence of external radio waves even at the outside of a communicable area. CONSTITUTION:A periodic data string transmitted from a tollgate antenna is received by an antenna 1, detected by a detection diode 2 and amplified by an amplifier 3. By half-wave-rectifying the output of the amplifier 3 by a rectifier diode 4 and blunting the waveforms by an LPF 5, the envelope of the data string is obtained. By passing the output of the LPF 5 through a BPF 6, the DC components are removed and further, the output of the BPF 6 is accumulated by an integration circuit 7. The output of the integration circuit 7 is compared with a set value by a comparator 8 and when it is the set value or more, the out put of the same comparator 8 is turned to a high level. Then, the interruption inputted from a data holding circuit 9 to the CPU 10, the CPU 10 is excitated, a limiter amplifier 11 is excited by an instruction from the CPU 10 and a data transmission/reception enabling state is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contactless IC card for wirelessly communicating with a main body side antenna such as a tollgate antenna in an unmanned tollgate, and particularly to a communication possible area. The present invention relates to a communication area detection circuit of a non-contact IC card for detecting that it has entered.

[0002]

2. Description of the Related Art In recent years, in a toll collection system for toll motorways, a non-contact IC card has been introduced to wirelessly transmit data between an antenna at a toll gate and a non-contact IC card carried by a user. , Research is underway to collect fees automatically and without stopping the car. FIG. 3 shows an operational image of a toll collection system for a toll road using the contactless IC card.

In the figure, reference numeral 24 is a tollgate antenna, which is a non-contact IC card 2 carried by a user on the toll road 23.
The wireless communication is performed with the wireless communication terminal 1. The non-contact IC card 21 stores information such as a user number unique to the user (or the vehicle 22 on which the user rides). The non-contact IC card 21 may be attached to the inside of the windshield of the vehicle 22, for example.

Reference numeral 27 is a tollgate computer installed in the unmanned tollgate 26. The toll gate calculator 27 receives information such as a user number and an entrance toll gate number communicated from the non-contact IC card 21 via the toll gate antenna 24, calculates a deduction amount, and displays a message board 28 and the like. Use it to show the deduction amount and the remaining amount to the user. The tollgate computer 27 is installed in the central management center and communicates the withdrawal amount to the central computer 29 connected to the computer 27 through a communication line or the like.
Based on this, the system automatically withdraws the charges from the user's bank account.

By the way, the non-contact IC card 21 described above is used.
Has a function of detecting the communicable area 25 at the tollgate 26 (communication area detecting function). This is to reduce the consumption of the battery built in the non-contact IC card 21, and the communicable area 25 of the tollgate 26.
Other than the above, as described later, the non-contact IC card 2
The CPU, limiter amplifier, and the like of 1 are set in a dormant state. Then, when detecting the entry into the communicable area 25, the CPU, the limiter amplifier and the like of the non-contact IC card 21 are in the excited state, and the wireless communication with the tollgate antenna 24 can be performed. FIG. 4 shows the configuration of the communication area detection circuit of the conventional non-contact IC card 21 that realizes the above-described communication area detection function, and FIG. 5 shows the waveform of each part in the configuration.

In the configuration of FIG. 4, first, the carrier wave output from the tollgate antenna 24 as shown in FIG. 3 is received by the antenna 30 of the non-contact IC card 21, so that the reception shown in FIG. A waveform 39 is obtained. Then, the reception data (reception waveform) 39 of the antenna 30 is detected by the detection diode 31, and the output waveform 40 shown in FIG. 5B is obtained. Furthermore, the detection diode 3
The detection output (output waveform) 40 of No. 1 is amplified by the amplifier 32 to obtain the output waveform 41 shown in FIG.
Is compared with a certain set value.

The comparator 33 sets the output to a high level (High level) only while the output (output waveform) 41 of the amplifier 32 is equal to or more than the set value. This allows the comparator 3
An output like the waveform 42 shown in FIG. 5D is obtained from 3 and supplied to the data holding circuit 34.

The data holding circuit 34 includes a comparator 33.
Is set to a high level at the rising edge of the output (output waveform) 42 of, and the high level state is maintained for a certain period. This is because even if the non-contact IC card 21 enters the communicable area 25 of the tollgate as shown in FIG. 3 and the output (output waveform) 42 of the comparator 33 temporarily becomes high level, the radio wave is generated immediately after entering. The reception status of is unstable,
This is because there may be a low level (Low level) again as shown in FIG. Since the output of the data holding circuit 34 is input to the interrupt terminal of the CPU 35, it is necessary to change the level from the low level to the high level only once when entering the communicable area 25 of the tollgate to interrupt the CPU 35. Therefore, the output 4 of the comparator 33
When 2 becomes high level, the data holding circuit 34 needs to hold the high level state for a certain period of time as shown by a waveform 43 in FIG. 5 (e).

When the CPU 35 detects an interrupt from the data holding circuit 34, the CPU 35 changes from the idle state to the excited state. Then, the CPU 35 activates the power supply control circuit 37 to supply power to the limiter amplifier 36. As a result, the limiter amplifier 36 is also in the excited state, and communication is possible. This limiter amplifier 36 is
The data transmitted from the tollgate antenna 24 as shown in FIG. 3, received by the antenna 30 of the non-contact IC card (21), and detected by the detection diode 31 is amplified and transmitted to the CPU 35 as the reception data 38. Yes, Figure 4
In this configuration, the power consumption is the largest.

[0010]

However, in the conventional non-contact IC card configured as described above,
If the received power is higher than a certain value, the detection circuit operates, not limited to the tollgate (within the communicable area), and C
An interrupt factor for PU occurs. At this time, CP
Since the U and limiter amplifiers are in an excited state in which transmission and reception are possible, the battery is significantly consumed. That is, in the conventional non-contact IC card, the detection circuit for detecting the entry into the communicable area operates due to the noise of the external radio wave, and the CPU and the limiter are located at a place other than (the communicable area of) the tollgate. There was a problem that the amplifier was excited, and it was very vulnerable to noise from external radio waves.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to prevent interruption of the CPU due to the influence of external radio waves even outside the communicable area.
Another object of the present invention is to provide a communication area detection circuit for a non-contact IC card that can prevent the battery life from being shortened due to an erroneous operation outside the communication area.

[0012]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a radio wave radiated from a main body side antenna,
It is assumed that packets are modulated as a data string and transmitted periodically, and in the non-contact IC card (amplifies the data radiated from the main body side antenna, received by the antenna of the same card, and detected by the detection diode). Between the amplifier and the comparator (which compares the level of the received data with the set value), a rectifying diode for half-wave rectifying the output of the amplifier, a low-pass filter for blunting the output waveform of this rectifying diode, A bandpass filter for removing the DC component (direct current component) of the output waveform of the low-pass filter and an integrating circuit for accumulating the output of the band-pass filter and outputting it to the comparator are provided, and data from the antenna on the main body side is provided. The feature is that the columns are extracted.

[0013]

In the above arrangement, the waveform of the data string detected by the detection diode and amplified by the amplifier is blunted by the low-pass filter, the DC component is removed by the band-pass filter, and accumulated by the integrating circuit. . That is, the data string received and detected by the non-contact IC card is converted from frequency to voltage. Therefore, unless the data string is periodically received, the output voltage of the integration circuit does not exceed a certain set value, that is, the output of the comparator does not become high level, and the interrupt from the communication area detection circuit to the CPU does not occur. . As a result, the communication area detection circuit does not accidentally operate outside the communicable area due to the noise of the external radio wave, and the CPU and the limiter amplifier are not in the excited state, and the battery consumption can be prevented.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will now be described with reference to the drawings, when it is applied to a contactless IC card applied to a toll collection system for a toll road. FIG. 1 is a block diagram showing a configuration of a communication area detection circuit of a non-contact IC card in the embodiment, and FIG. 2 is a diagram showing waveforms of respective parts in the configuration of FIG.

In FIG. 1, reference numeral 1 denotes an antenna of a non-contact IC card, which receives radio waves radiated from the antenna at a toll gate. The radio wave radiated from this tollgate antenna is not a conventional carrier wave, but is the one that modulates the first packet necessary for communication for toll collection as a data string and is sent out periodically. Therefore, the reception waveform 14 of the antenna 1 in the configuration of FIG. 1 is as shown in FIG.

Received data (received waveform) 14 from the antenna 1
Is supplied to the detection diode 2 and is detected by the diode 2. The output waveform 15 of the detector diode 2 is shown in FIG.
As shown in (b), it has a detected waveform that allows confirmation of the contents of the data string. The output (output waveform) 15 of the detection diode 2 is amplified by the amplifier 3. The output waveform 16 of the amplifier 3 is shown in FIG.

The output (output waveform) 16 of the amplifier 3 is supplied to the rectifying diode 4 and half-wave rectified. The output of the rectifying diode 4 has its waveform blunted by a low-pass filter (hereinafter referred to as LPF) 5. As a result, the envelope of the data string is extracted. The output waveform 17 of the LPF 5 is shown in FIG.

The output (output waveform) 17 of the LPF 5 is passed through a bandpass filter (hereinafter referred to as BPF) 6 to remove its DC component. As a result, from the BPF 6, only a signal centered on the repetition frequency of the data string is obtained, as in the output waveform 18 shown in FIG.

The output (output waveform) 18 of the BPF 6 is supplied to the integrating circuit 7. The integrating circuit 7 stores the output (output waveform) 18 of the BPF 6. As a result, the output waveform 19 as shown in FIG. 2 (f) is obtained from the integrating circuit 7.

The output (output waveform) 19 of the integrating circuit 7 is supplied to the comparator 8. The comparator 8 outputs the output (output waveform) 19 of the integration circuit 7 (similar to the comparator 33 in the communication area detection circuit of the conventional non-contact IC card shown in FIG. 4 comparing the output of the amplifier 32 with the set value). If the output (output waveform) 19 of the integrating circuit 7 is larger than the set value and compared with a set value, the comparator 8
Make sure the output of is at a high level. The output waveform 20 of the comparator 8 is shown in FIG.

The output (output waveform) 20 of the comparator 8 is supplied to the data holding circuit 9. The data holding circuit 9
C which is set to a high level at the rise of the output (output waveform) 20 of the comparator 8 and constitutes the center of the non-contact IC card
An interrupt to PU10 is generated.

When the CPU 10 detects an interrupt from the data holding circuit 9 (of the communication area detection circuit), it determines that it has entered the communication area and changes itself from the dormant state to the excited state and acts on the power supply control circuit 12. Then, the limiter amplifier 11 is supplied with power (the amplifier 11 is put into an excited state), and the non-contact IC card in which the limiter amplifier 11 is mounted is brought into a communicable state. In this state, the limiter amplifier 11 is received by the antenna 1 of the non-contact IC card,
The data detected by the detection diode 2 is amplified and transmitted to the CPU 10 as the reception data 13.

Although the present invention has been described as applied to the toll collection system for toll motorways, the present invention wirelessly communicates between the main body side antenna and the non-contact IC card in a management system for physical distribution and the like. The same can be applied to any non-contact IC card system in which the main body side identifies the moving body by performing the above.

[0024]

As described above in detail, according to the present invention, the envelope of the periodic data string output from the antenna on the main body side is converted from frequency to voltage, and the result of comparison between the integrated value and the set value is converted. According to the configuration, an interrupt to the CPU in the non-contact IC card is generated. Therefore, the interrupt to the CPU does not occur in a place where a periodic data string is not received, such as outside the communicable area, and CPU and (same C
The limiter amplifier does not enter the excited state in which data can be transmitted / received, and the limiter amplifier detects the entry into the communication area only from the received power level of the carrier wave. As compared with the communication area detection circuit in (1), the occurrence of interruption by external radio waves is eliminated, and the battery life can be significantly improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a communication area detection circuit of a non-contact IC card according to an embodiment of the present invention.

FIG. 2 is a diagram showing a waveform of each part in the configuration of FIG.

FIG. 3 is a diagram showing an operation image of a toll collection system for a toll road using a contactless IC card.

FIG. 4 is a block diagram showing a configuration of a communication area detection circuit of a conventional non-contact IC card.

5 is a diagram showing waveforms at various parts in the configuration of FIG.

[Explanation of symbols]

1 ... Antenna, 2 ... Detection diode, 3 ... Amplifier, 4 ...
Rectifier diode, 5 ... LPF (low pass filter), 6
... BPF (band pass filter), 7 ... integrator circuit, 8 ...
Comparator, 9 ... Data holding circuit, 10 ... CPU, 1
1 ... Limiter amplifier, 12 ... Power supply control circuit, 14 ... Antenna 1 reception waveform, 17 ... LPF5 output waveform, 18 ...
Output waveform of BPF 6, 19 ... Output waveform of integrating circuit 7, 2
0 ... Output waveform of the comparator 8.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical display location G07B 11/00 8111-3E 15/00 L 8111-3E H04B 7/26 E 9297-5K (72) Inventor Masayuki Yasui 1-1-1 Wadasaki-cho, Hyogo-ku, Kobe-shi, Hyogo Prefecture Mitsubishi Heavy Industries, Ltd. Kobe Shipyard

Claims (1)

[Claims] 1. A non-contact IC card having a built-in CPU for wirelessly communicating with a main body side antenna within a communicable area, wherein a radio wave radiated from the main body side antenna is received and detected. , A rectifying diode for half-wave rectifying the waveform obtained by amplification, a low-pass filter for blunting the output waveform of this rectifying diode, and a band-pass filter for removing the DC component of the output of this low-pass filter. An integration circuit for accumulating the output of the bandpass filter, and a comparator for comparing the output of the integration circuit with a set value to detect that the output is greater than or equal to the set value. The radio waves radiated from the antenna are
A packet is modulated as a data string and output periodically, and by receiving this data string periodically, the output of the integration circuit becomes equal to or more than the set value,
A communication area detecting circuit in a non-contact IC card, wherein an interrupt to the CPU indicating that the CPU has entered the communicable area is generated and the CPU is brought into an excited state.