JP2000049654A - Rfid system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the power consumption of a reader without sacrificing a communication distance and response. SOLUTION: The passive type RFID (Radio Frequency Identification) system has a control circuit 24 which sets the antenna output electric power of an interrogation radio wave of the reader 10 according to whether or not an answer radio wave is received from a noncontact identification tag. When no answer radio wave is received from the said noncontact identification tag, the antenna output electric power of the interrogation radio wave is set to two kinds of antenna output electric power having a nearly double intensity difference at predetermined constant intervals of time. When the response radio wave is received from the noncontact identification tag, the antenna output electric power is set continuously to the current antenna output electric power for a period needed for identification information transmission and reception and when the identification information reception ends, it is set to the other kind of antenna output electric power.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an RFID system using a passive non-contact identification tag having no battery therein, and more particularly to a reduction in power consumption of a reader.

[0002]

2. Description of the Related Art Conventionally, an RFID using a passive type non-contact identification tag has been used as a non-contact type individual identification system.
(Radio Frequency Identification) system.
FIG. 5 is a block diagram of a conventional RFID system.
Is a reader that transmits an interrogation radio wave, and 2 is a contactless identification tag that, when receiving the interrogation radio wave from the reader 1, returns a response radio wave including identification information for individual identification.

[0003] Also, 11 is a transmission circuit for generating a carrier wave,
A transmitting / receiving antenna 12 transmits the carrier wave as an interrogation radio wave and receives a response radio wave. A receiving circuit 13 extracts identification information from the response radio wave received by the antenna 12.
1 is a transmitting / receiving antenna that receives a query radio wave and transmits a response radio wave, 22 is a receiving circuit that generates a clock signal CLK from the query radio wave received by the antenna 21, 23 is a rectifier circuit that converts the query radio wave into electric power, and 24 is a signal. A control circuit that outputs identification information when CLK is input, and a transmission circuit 25 that multiplexes identification information on the interrogation radio wave received by the antenna 21.

Next, the operation of such an RFID system will be described. The transmission circuit 11 in the reader 1 outputs a carrier wave to the transmission / reception antenna 12, and the antenna 12 transmits this as an interrogation radio wave of the frequency f1. FIG. 6 is a diagram showing the antenna output power of this interrogation radio wave. The rectifier circuit 23 in the contactless identification tag 2 converts the interrogation radio wave received by the transmitting / receiving antenna 21 into electric power. When this power is supplied, the control circuit 24 starts operating. On the other hand, the receiving circuit 22 generates the clock signal CLK from the interrogation radio wave received by the antenna 21.

When the control circuit 24 receives the clock signal CLK from the receiving circuit 22, it reads the identification information from an internal storage circuit (not shown). Subsequently, the transmission circuit 25 uses the interrogation radio wave received by the transmission / reception antenna 21 as a carrier, multiplexes the identification information with the carrier, and outputs the multiplexed identification information to the antenna 21. In this way, the frequency of the carrier is f1 ± f
It becomes 2. Thus, the frequency f
A response radio wave of 1 ± f2 is transmitted. Next, the reading device 1
The receiving circuit 13 extracts identification information from the response radio wave received by the transmitting / receiving antenna 12.

[0006] By obtaining the identification information from the non-contact identification tag 2 in this way, the tag 2 (or an object with the tag 2) can be identified. In such an RFID system, the interrogation radio wave transmitted from the reading device 1 is used as a carrier of the identification information transmitted from the non-contact identification tag 2 to the reading device 1 and supplies driving power to the control circuit 24. It is also used as a feed wave.

[0007] In such a conventional communication method of the RFID system, the reading device 1 continues to output the interrogation radio wave so that the communication can be performed even when the non-contact identification tag 2 enters the communication area (see FIG. 1). 6). Therefore, if the electric field strength of the interrogation radio wave is increased, the communicable distance between the reader and the tag can be increased. However, this RFID system can be used as an inductive communication device under the Radio Law (that is, it does not require the approval of the Minister of Posts and Telecommunications). ), The electric field strength of the interrogation radio wave cannot be made larger than the value specified by the Radio Law.

[0008]

As described above, in the state of waiting for communication with the non-contact identification tag, it is necessary to constantly emit interrogation radio waves from the transmitting / receiving antenna of the reader. For this reason, the reading device consumes considerable power even in the standby state, and it is required to reduce the power consumption. For this purpose, a method for reducing the antenna output power of the interrogation radio wave has been devised. However, reducing the antenna output power as in this method, that is, reducing the power available for the non-contact tag, has the problem of shortening the communication distance. SUMMARY An advantage of some aspects of the invention is to provide an RFID system that can maintain a communication distance as before and reduce power consumption of a reading device without deteriorating responsiveness. Aim.

[0009]

SUMMARY OF THE INVENTION The present invention provides the following means for solving this problem.

[0010] An RFID system according to a first aspect of the present invention includes a non-contact identification tag that, when receiving an interrogation radio wave, obtains driving power for an internal circuit from the radio wave and transmits a response radio wave including identification information; An RFID system comprising a reader that transmits a radio wave and receives a response radio wave, wherein the antenna output power of the interrogation radio wave of the reader is changed according to whether or not the response radio wave is received from the non-contact identification tag. It has a control circuit for setting as follows. (1) When the response radio wave from the non-contact identification tag is not received, the antenna output power of the interrogation radio wave is set to two types of antenna output powers having an intensity difference of about twice at predetermined time intervals. (2) When a response radio wave is received from the contactless identification tag, the antenna output power is set to the current antenna output power for a period necessary for transmitting and receiving the identification information.
Set the type of antenna output power.

The RFID system according to a second aspect of the present invention is the RFID system according to the above-mentioned RFID system, wherein the reading device changes the antenna output power of the interrogation radio wave in response to the reception or non-reception of the response radio wave from the non-contact identification tag. It has a control circuit for setting as follows. (1) When the response radio wave from the non-contact identification tag is not received, on / off of the antenna output power of the interrogation radio wave is set at a predetermined constant time interval, and when the response radio wave is turned on, the predetermined constant time interval is set. To set two types of antenna output powers with almost twice the intensity difference. (2) When receiving a response radio wave from the non-contact identification tag, the antenna output power should be kept set to the current antenna output power for a period necessary for transmitting and receiving the identification information. (3) When the transmission and reception of the identification information is completed, the antenna output power is set to off for a predetermined time, and then another one is set.
Set the type of antenna output power.

[0012]

Next, embodiments of the present invention will be described in detail with reference to examples.

[0013]

Embodiment 1 FIG. 1 is a block diagram of an RFID system showing an embodiment of the present invention, and the same components as those in FIG. 5 are denoted by the same reference numerals. In FIG. 1, 1a is a reading device,
Reference numeral 14a denotes a control circuit that sets the antenna output power of the interrogation radio wave of the reader 1a as follows when the response radio wave from the non-contact identification tag 2 is received or not.

(1) When the response radio wave from the non-contact identification tag 2 is not received, the antenna output power of the interrogation radio wave is increased twice at a predetermined time interval of a predetermined time interval ratio of 1 to 2 with an intensity difference of about twice. Set the type of antenna output power. (2) When a response radio wave is received from the contactless identification tag, the antenna output power is set to the current antenna output power for a period necessary for transmission and reception of the identification information.
Set the type of antenna output power. 2A and 2B are diagrams showing the antenna output power of the interrogation radio wave of the reader 1a. FIG. 2A shows a state when the response radio wave from the contactless identification tag 2 is not received, and FIG. 2B shows a state when the response radio wave is received. FIG.

Next, the operation of such an RFID system will be described. Since the transmission and reception of the identification information is the same as the conventional example, the description is omitted, and only the setting of the antenna output power will be described. When the non-contact identification tag 2 is not within the response range, the non-contact identification tag 2 cannot generate enough power to drive its built-in circuit with the interrogation radio wave from the reader 1a. As shown in ()), two types of antenna output powers having almost twice the intensity difference are alternately output at a fixed time interval of a predetermined time interval ratio of 1: 1.

Now, in such a state, the non-contact identification tag 2
Is within the response range, as shown in (1) of FIG. 2B, a response radio wave including identification information is first emitted from the contactless identification tag 2 in an area where the antenna output power is large, and Transmission and reception of information is performed. During this period, the reading device 1a keeps the same antenna output power, then halves it to almost half the antenna output power, and waits for the next contactless identification tag 2 to enter the response range. Although not shown, if the contactless identification tag 2 falls within the response range at approximately half the antenna output power after the transmission and reception of the identification information,
The transmission / reception of the identification information is executed with the antenna output power.

When the next non-contact identification tag 2 does not come within the response range, it is the same as when the above-mentioned non-contact identification tag 2 is not within the response range. The operation is as shown in FIG. Where 2
Higher output power of different types of antenna
If the antenna output power is the same as the system, as described above, even if the intensity of the antenna output power of the interrogation radio wave from the reader 1a is increased or decreased, the identification information can be transmitted and received without impairing the communication distance and the responsiveness. Becomes

[0018]

[Embodiment 2] FIG. 3 shows another embodiment of the present invention.
FIG. 6 is a block diagram of the FID system, and the same components as those in FIG. 5 are denoted by the same reference numerals. In FIG. 3, reference numeral 1b denotes a reader, and 14b denotes a control circuit for setting the antenna output power of the interrogation radio of the reader 1a as follows when receiving or not receiving a response radio wave from the contactless identification tag 2. is there.

(1) When the response radio wave from the non-contact identification tag is not received, the antenna output power of the interrogation radio wave is set on / off at predetermined time intervals at a predetermined time interval ratio of 1: 5. When this is done, the antenna output power should be set to a predetermined time interval ratio of 1 to 1 and the antenna output power having an intensity difference of about twice at regular time intervals. (2) When receiving a response radio wave from the non-contact identification tag, the antenna output power should be kept set to the current antenna output power for a period necessary for transmitting and receiving the identification information. (3) When the transmission and reception of the identification information is completed, the antenna output power is set to off for a predetermined time, and then another one is set.
Set the type of antenna output power. 4A and 4B are diagrams showing the antenna output power of the interrogation radio wave of the reader 1b. FIG. 4A shows the state when the response radio wave from the contactless identification tag 2 is not received, and FIG. 4B shows the state when the response radio wave is received. FIG.

Next, the operation of such an RFID system will be described. Since the transmission and reception of the identification information is the same as in the conventional example, a description thereof will be omitted, and only the setting of the antenna output power will be described as in the first embodiment. When the non-contact identification tag 2 is not within the response range, the non-contact identification tag 2 cannot generate enough power to drive the built-in circuit from the interrogation radio wave from the reader 1b.
As shown in (A), a predetermined time interval ratio of 1: 5
To turn on / off the antenna output power of the interrogation radio at fixed time intervals.
When the power is turned off and the power is turned on, the antenna output power having an intensity difference of almost twice at a predetermined time interval is alternately output at a predetermined time interval ratio of 1: 1.

Now, in such a state, the non-contact identification tag 2
Is within the response range, as shown in (1) of FIG. 4B, first, in a region where the antenna output power is large, a response radio wave including identification information is radiated from the non-contact identification tag 2, and identification is performed. Transmission and reception of information is performed. This period identification device 1b keeps the same antenna output power, then turns off the antenna output power, then halves it to approximately half the antenna output power, and waits for the next contactless identification tag 2 to enter the response range. Will be. Although not shown, if the contactless identification tag 2 falls within the response range at approximately half the antenna output power after the transmission and reception of the identification information, the transmission and reception of the identification information with the antenna output power may be performed. Becomes

When the next non-contact identification tag 2 does not come within the response range, it is the same as when the above-mentioned non-contact identification tag 2 is not within the response range. The operation is as shown in FIG. Where 2
Higher output power of different types of antenna
Assuming that the output power is the same as the antenna output power of the system, as described above, even if the intensity of the antenna output power of the interrogation radio wave from the reader 1b is increased or decreased, the identification information can be transmitted and received without impairing the communication distance and the responsiveness Becomes

In the present embodiment, the antenna output power of the interrogation radio wave of the reader is set to be approximately twice as large as two types. Of course, the ratio may be changed, and it is needless to say that the fixed time interval and the one other than this embodiment can be appropriately selected as long as no problem occurs in the communication distance and the response.

[0024]

According to the first aspect of the present invention, when the non-contact identification tag is not within the response range, the non-contact identification tag generates enough power to drive the built-in circuit from the interrogation radio wave output from the reader. Because it is not possible, the predetermined time interval ratio 1
Two types of antenna output powers having an intensity difference of about two times are alternately output at a fixed time interval of one to one. When the contactless identification tag enters the response range, the non-contact identification tag is output in a region where the antenna output power is large. The response radio wave is radiated from the contact identification tag, and the transmission and reception of the identification information are performed. During this time, the reader keeps the same antenna output power, then halves it to almost half the antenna output power, and the next contactless identification tag responds. If the contactless identification tag falls within the response range at approximately half the antenna output power after transmitting / receiving the identification information, the transmission / reception of the identification information shall be performed with the antenna output power. And

For this reason, assuming that the higher power of the two types of antenna output power is the same as the antenna output power of the conventional RFID system, as described above, the antenna output power of the interrogation radio wave output by the reader is Even if the strength is added, it is possible to transmit and receive the identification information without impairing the communication distance and the responsiveness. Therefore, according to the RFID system according to the present invention, it is possible to construct a non-contact solid-state identification system having low power consumption, excellent responsiveness, and excellent communication distance.

According to the second aspect of the present invention, when the non-contact identification tag is not within the response range, the non-contact identification tag generates enough power to drive the built-in circuit from the interrogation radio wave output from the reader. Because it is not possible, the predetermined time ratio 1
The antenna output power of the interrogation radio wave is turned on / off at fixed time intervals at a ratio of 5, and when turned on, a predetermined time ratio of 1
When the antenna output power of almost twice the intensity difference is alternately output at a fixed time interval of one to one and the contactless identification tag comes within the response range, first, in the area where the antenna output power is large, the contactless identification tag A response radio wave is radiated, and transmission / reception of identification information is performed. During this period, the reading device holds the same antenna output power, then turns off the antenna output power, and thereafter halves the antenna output power to almost half, and then returns to the next antenna. Waiting for the contact identification tag to enter the response range, and after transmitting and receiving the identification information, if the contactless identification tag enters the response range when the antenna output power is almost half, the identification is performed with the antenna output power. Send and receive information.

For this reason, assuming that the higher power of the two types of antenna output power is the same as the antenna output power of the conventional RFID system, as described above, the antenna output power of the interrogation radio wave output by the reader is Even if the strength is added, it is possible to transmit and receive the identification information without impairing the communication distance and the responsiveness. Therefore, according to the RFID system according to the present invention, the transmission of the interrogation wave is periodically stopped in addition to the first aspect of the present invention. It is possible to construct an individual identification system.

[Brief description of the drawings]

FIG. 1 is a block diagram of an RFID system showing one embodiment of the present invention.

FIG. 2 is a diagram showing antenna output power of an interrogation wave of the reader of the invention of FIG. 1;

FIG. 3 is a block diagram of an RFID system showing another embodiment of the present invention.

FIG. 4 is a diagram showing the antenna output power of the interrogation wave of the reader of FIG. 3;

FIG. 5 is a block diagram of a conventional RFID system.

FIG. 6 is a diagram showing antenna output power of a query radio wave of a conventional reader.

[Explanation of symbols]

 1, 1a, 1b reader 2 non-contact identification tag 11 transmission circuit 11 transmission circuit 12 transmission / reception antenna 13 reception circuit 14a, 14b control circuit 21 transmission / reception antenna 22 reception circuit 23 rectification circuit 24 control circuit 25 transmission circuit

Claims (2)

[Claims] 1. A non-contact identification tag that, upon receiving an interrogation radio wave, obtains driving power for an internal circuit from the radio wave and transmits a response radio wave including identification information, and transmits the response radio wave by transmitting the interrogation radio wave. RFID equipped with a reader for receiving
An RFID system, comprising: a control circuit that sets an antenna output power of an interrogation radio wave of the reader as follows in response to reception or non-reception of a response radio wave from the non-contact identification tag. . (1) When the response radio wave from the non-contact identification tag is not received, the antenna output power of the interrogation radio wave is set to two types of antenna output powers having an intensity difference of about twice at predetermined time intervals. (2) When a response radio wave is received from the contactless identification tag, the antenna output power is set to the current antenna output power for a period necessary for transmitting and receiving the identification information.
Set the type of antenna output power. 2. The RFID system according to claim 1, further comprising a control circuit for setting the antenna output power of the interrogation radio wave of the reader as follows in response to reception or non-reception of a response radio wave from the non-contact identification tag. An RFID system, characterized in that: (1) When the response radio wave from the non-contact identification tag is not received, on / off of the antenna output power of the interrogation radio wave is set at a predetermined constant time interval, and when the response radio wave is turned on, the predetermined constant time interval is set. To set two types of antenna output powers with almost twice the intensity difference. (2) When receiving a response radio wave from the non-contact identification tag, the antenna output power should be kept set to the current antenna output power for a period necessary for transmitting and receiving the identification information. (3) When the transmission and reception of the identification information is completed, the antenna output power is set to off for a predetermined time, and then another one is set.
Set the type of antenna output power.