WO2007072563A1

WO2007072563A1 - Rfid system and rfid reading apparatus

Info

Publication number: WO2007072563A1
Application number: PCT/JP2005/023629
Authority: WO
Inventors: Hiroshi Tanae
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2005-12-22
Filing date: 2005-12-22
Publication date: 2007-06-28

Abstract

A RFID system and an RFID reading apparatus wherein a spectrum spread modulation scheme can be directly applied to an existing RFID, which exhibits a low power consumption and which is small-sized and low at cost, to increase the communication distance. In this RFID system and RFID reading apparatus, during a CW transmission, an ASK modulation data and a spread code are always set to fixed values, the addition of carrier (carrier wave CW) is rendered off, and the spread process is not performed. During a command transmission, the ASK modulation data is set to a transport data (command data), the spread code is always set to the fixed value, and the addition of carrier is rendered off. In this way, the existing RFID (200) can be used to recognize a command from a reader (900). During a transmission and a response reception, if a response wave is to be obtained, the transport wave is multiplied by the spread code for a spectrum spreading and the addition of carrier is rendered off. This can increase the communication distance of a reflected response wave that is PSK-modulated (or ASK-modulated) and reflected by the RFID (200).

Description

Specification

RFID system and RFID reader

Technical field

[0001] The present invention relates to an RFID system and an RFID reading apparatus to which a spread spectrum method is applied as a reading method of a wireless IC tag.

Background art

Conventionally, an RFID (Radio Frequency Identification) system is known as an information reading system for identifying and managing a person or an object with a small wireless chip.

[0003] The RFID system has been studied as a product identification 'management technology to replace barcodes in the distribution industry, but is gaining attention as a fundamental technology for promoting the use of IT in society.

[0004] In an RFID system, a reader, which is an RFID reader for reading RFID data, stores data in a wireless IC tag (RFID) with a size of several centimeters, and communicates with the RFID by radio waves and electromagnetic waves.

[0005] RFID includes a label type, a card type, a coin type, a stick type, and the like having a communication distance of about several millimeters to several tens of meters, and is used depending on the application.

[0006] Further, this type of RFID has RFID power S of active type, passive type, semi-passive type and the like.

[0007] An active RFID has a built-in battery and can communicate with a reader over a long distance of about several tens of meters.

[0008] Passive type RFID is a type that does not incorporate a battery and obtains an electromotive force by a transmission wave from a reader by a non-contact power transmission technique from the antenna side.

[0009] Semi-passive RFID uses a power regeneration circuit that is provided by another means that is not a received wave from a reader.

In the RFID reading operation in such an RFID system, first, the reader sends a transmission wave to the surrounding RFID.

[0011] The RFID receiving the transmission wave rectifies the transmission wave from the built-in battery or the reader. The internal circuit is driven by the electromotive force obtained in the above.

[0012] When the circuit operates, the RFID reads a command placed on a transmission wave, and returns (reflects) a response wave carrying information such as an ID number to the reader in accordance with the read command.

[0013] By the way, a general passive RFID can be used semi-permanently because it does not have a battery, but it normally communicates with a reader at a short distance of several millimeters or less using a frequency band of 13 MHz. There are a lot of types to do.

[0014] Since this type of RFID responds by contacting the reader at a short distance, it can generate a fairly powerful electromotive force by magnetic induction such as an electromagnetic coil, and incorporates a relatively complex microcomputer. Can be operated without using a battery.

[0015] Thus, this type of general RFID has been used at a relatively short distance until now.

In recent years, the use of a high frequency band such as 900 MHz or 2.4 GHz has been studied for use in an RFID system that can communicate with a reader even at a communication distance of several tens of meters from the reader.

As such an RFID system, for example, when a truck loaded with a load passes through a gate, the RFID attached to the truck load is read by a reader to manage the shipment and arrival of the load. The introduction to is considered.

[0017] On the other hand, this type of RFID is required to be able to communicate within a range of several tens of meters, and to have a built-in chip that is as small as possible and inexpensive. It has also been studied to form by printing with a printer.

[0018] However, in such an RFID system, when the reader reads the RFID, it is necessary that the radio wave of the reader has a communication power intensity enough to reciprocate between the reader and the RFID. .

[0019] For this reason, in the RFID system that requires long-distance communication, when the conventional RFID having a small and inexpensive configuration as described above is used, the command transmission wave transmitted from the reader is Even if it reaches the receiver, the communication power intensity of the response wave reflected by the RFID is weak, so that the response wave from the RFID does not reach the reader.

[0020] In order to solve such a problem, it is necessary to make a response wave from RFID reach the reader. It is necessary to increase the communication distance between the RFID and the RFID, especially the communication distance of the RFID response wave.

[0021] In the conventional RFID system, as a method of extending the communication distance between the reader and the RFID, it is effective to perform spread spectrum modulation on the transmission wave of the reader by multiplying the transmission wave of the reader by the spread code generator and the spread code. It is.

Conventionally, as an RFID system using such a spread spectrum modulation method, spread code modulation is applied to an interrogator (reader) interrogator (reader) that communicates with a responder (RFID) attached to a mobile body in a contactless manner. There is known a mobile unit identification device that is provided with means and a spreading code demodulation means in the response signal receiving unit of the interrogator (see, for example, Patent Document 1).

As shown in FIG. 14, the mobile object identification device described in Patent Document 1 generates a carrier wave from the carrier wave oscillator 11 of the interrogator Q and spreads it using the spreading code generated by the spreading code generator 12. The modulator 13 performs spread spectrum modulation on the carrier wave and radiates a broadband signal through the antenna 14.

[0024] The transponder A receives the spectrum-spread signal radiated from the interrogator Q by the antenna 15, thereby modulating the signal received using the code modulator 17 with the data in the memory 16, This modulated signal (broadband signal) is radiated (reflected) by the antenna 15.

The interrogator Q receives the wideband signal radiated from the responder A by the antenna 18, so that the interpolator 20 uses the same spreading code sequence as that produced by the spreading code generator 19 to perform the spreading / demodulation 20 Performs spread spectrum demodulation using, and narrows the spectrum spread broadband signal

Then, the interrogator Q reads the data held by the responder A by demodulating the signal that has been spread demodulated using the spread demodulator 20 with the code demodulator 21.

[0027] In this mobile unit identification device, the noise of the other device power received by the interrogator Q is a diffusion demodulator.

20 spreads to a wideband signal, so that the influence of noise on the code demodulator 21 can be significantly reduced.

[0028] In addition, since this mobile object identification device is provided with the spread code generator 12 and the spread modulator 13 in the interrogator Q, the responder A can be reduced in size and weight.

[0029] Further, since the responder A of the mobile object identification device requires less current consumption, the built-in battery can have a longer life when configured to operate with a battery. [0030] As an RFID system using another spread spectrum modulation method, data can be read and written even in the presence of multiple interrogators and radio wave reflecting objects around the responder. A mobile identification communication system that can obtain a range is known (for example, see Patent Document 2).

[0031] As shown in FIG. 15, the interrogator Q in the mobile unit identification communication system described in Patent Document 2 reads the information from the responder A, and the interrogator signal generation means 22 converts the carrier signal into, for example, spread spectrum modulation. The transmitted carrier spread signal 23 is radiated from the transmitting antenna 25 as the interrogation signal 26 via the switching means 24.

[0032] The interrogator Q changes the operation mode of the responder A, and the data storage means of the responder A

When sending information to write data to 27, the carrier wave spread signal 23 is amplitude-shift modulated by the amplitude shift modulation means 28 of the interrogation signal generating means 22, and this amplitude shift modulated signal is passed through the switching means 24. Radiated as interrogation signal 26 from transmitting antenna 25.

When the transponder A enters the communication area of the interrogator Q, the interrogator Q receives the interrogator signal 26 output from the interrogator Q and detects it.

Alternatively, the transponder A changes the reflection condition by, for example, reflecting or terminating the interrogation signal 26 by the detection / data modulation means 30 according to the data held in the data storage means 27, and shifts the amplitude. A spread modulation signal that has been modulated in the form of modulation or the like is obtained, and this signal is reflected from the response antenna 29 as a response signal 31.

[0035] The interrogator Q can share the signal from the interrogation signal generating means 22 for transmission and reception, and has a receiving antenna.

The response signal 31 received at 32 is demodulated from the demodulation signal 34 obtained by frequency conversion by the reception demodulation means 33.

It should be noted that the interrogator Q switches the switching means 24 by the switching signal 36 from the communication state determination means 35 and changes the inquiry signal 26 depending on whether the communication is information reading or writing. .

[0037] The interrogator Q in the mobile identification communication system emits different carrier spread signals 23 obtained by performing spread spectrum modulation on the carrier signal, so that even if there are a plurality of interrogators Q, the interrogator Q does not correspond. Are uncorrelated in the demodulation process, only correlated signals Are demodulated, so that they can be operated without mutual influence.

[0038] Further, the interrogator Q in this mobile unit identification communication system can share the spread modulation signal for transmission and reception, and does not need to take complicated synchronization, so that the configuration can be simplified.

[0039] Furthermore, the interrogator Q in this mobile unit identification communication system can read the data of the responder A even in a state where the spread modulation is performed, and the responder A can receive data including control data. You can also send and write.

[0040] Further, as an RFID system using another spread spectrum modulation scheme, intersymbol interference is reduced by assigning codes having the same spreading code and different periods to each of a plurality of responders. A transbonder is known in which the number of responders that can be simultaneously received is increased (see, for example, Patent Document 3).

[0041] The transbonder described in Patent Document 3 includes an interrogator Q interrogator generator as shown in FIG.

The interrogation wave generated at 37 is transmitted by the antenna 38.

[0042] The transponders A and B receive the interrogation wave from the interrogator Q by the antennas 39 and 40, and transmit the response signal to the interrogator Q.

At this time, from the responder A, the response signal to which the spreading code having the period tl is assigned by the spreading code generator 41 is transmitted by the antenna 42.

[0044] Further, from the responder B, the response signal to which the spreading code of the period t2 is assigned by the spreading code generator 43 is transmitted by the antenna 44.

Next, the response signals transmitted from the responders A and B are received by the antenna 45 of the interrogator Q.

[0046] At this time, the interrogator Q multiplies the received signal by the interrogator wave from the interrogator generator 37 by the multiplier 46 to remove the interrogation wave component, and extracts the spread code from each response signal.

[0047] The extracted spreading code is input to the correlator 48 of the correlator 47, correlated with the spreading code of the spreading code generator 49, and a correlation value is obtained.

Here, the correlation value obtained by correlator 47 is assigned a spreading code with period tl to the response signal from responder A, and a spreading code with period t2 is assigned to the response signal from responder B. Et Therefore, the autocorrelation peak of the responder A with the period tl and the autocorrelation peak of the responder B with the period t2 appear.

Next, the correlation value obtained by the correlation unit 47 is input to the decoding unit 50.

[0050] In decoding section 50, period determination circuit 51 determines the period of the spreading code, and identifies and separates the spreading code of responder A and the spreading code of responder B.

[0051] Here, the period determination circuit 51 detects how many response signals are received from the number of responders by examining the number of periods in which the autocorrelation peak appears.

[0052] In addition, the cycle determination circuit 51 detects which responder force response signal is received by checking whether the cycle in which the autocorrelation peak appears is the same as the preset cycle.

[0053] The correlation value from each of the responders A and B identified and separated in this way is a reception presence / absence determination circuit.

It is input to 52 and 53 to determine the presence or absence of a received signal.

[0054] When there is a reception signal from the responder A, data for the response device A is output from the reception presence / absence determination circuit 52, and when there is a reception signal from the response device B, a reception presence / absence determination circuit 53 responder B data is output.

[0055] Thereby, in this transbonder, each of the responders A, B with respect to the plurality of responders A, B

By assigning the same spreading code for each B and having a different period, intersymbol interference is reduced and the autocorrelation peak identification capability is improved, so that the number of receivable responders can be increased.

[0056] In addition, the period of the spreading code assigned to the plurality of responders A and B is determined in advance, and the period of the spreading code for which the interrogator Q obtains the correlation value with the spreading code of the plurality of responders A and B is determined. By determining, the number of responders simultaneously receiving can be specified.

Patent Document 1: JP-A-5-297131

Patent Document 2: JP-A-7-84040

Patent Document 3: Japanese Patent Laid-Open No. 2003-78445

Disclosure of the invention

Problems to be solved by the invention

[0057] However, in the conventional RFID system, it is transmitted from a reader (interrogator). When the transmission wave to be transmitted is spread spectrum modulated, the RFID (responder) having the conventional configuration described above cannot recognize the command transmitted from the reader.

That is, in order for RFID to recognize a command of a transmission wave that has been subjected to spread spectrum modulation, it is necessary to change the RFID to one that corresponds to the spread spectrum modulation method.

[0059] Specifically, it is necessary to reconfigure the RFID so that a command can be recognized by providing a despreading demodulation circuit for determining whether or not to respond according to a command instruction from the reader inside the RFID.

However, when such a spread spectrum signal demodulating circuit is provided inside the RFID, it is necessary to detect the spreading code, so the RFID circuit scale becomes large and complicated, and the power consumption increases. End up.

[0061] Further, in recent RFID systems, it is required to configure the RFID with a chip that is as small and inexpensive as possible, and the use of passive RFID that does not incorporate a battery is becoming mainstream.

[0062] Under such circumstances, providing a despreading demodulation circuit in RFID leads to downsizing of RFID and low cost.

[0063] Further, since the passive RFID does not have a built-in battery, it is difficult to secure an electromotive force sufficient to stably drive the RFID even if it is provided with a despreading demodulation circuit.

[0064] Therefore, in the RFID system using the spectrum spread modulation method, the conventional RF

It was difficult to adapt ID (especially passive RFID) to spread spectrum modulation as it is.

As described above, the RFID system using the spread spectrum modulation method is less feasible than the conventional RFID system using the general RFID using the ASK (Amplitude Shift Keying) modulation method.

[0066] In addition, in the case of RFID that performs clock extraction, it is difficult to correctly extract the clock from the spread spectrum signal.

[0067] Furthermore, in the RFID system using the spectrum spread spectrum modulation system, the spectrum spread signal cannot obtain a stable detection potential with respect to the time axis. The conversion efficiency is worse. [0068] For this reason, this type of RFID system has a problem that the spread spectrum modulation method cannot be applied as it is to a conventional low power consumption, small and inexpensive existing RFID.

An object of the present invention is to provide an RFID system and an RFID reader capable of extending a communication distance by directly applying a spread spectrum modulation method to an existing RFID that is low in power consumption, small and inexpensive. .

Means for solving the problem

[0070] An RFID system of the present invention includes an RFID having storage means storing data, and an RFID reader that reads the data stored in the storage means by wireless communication with the RF ID. When transmitting a command to the RFID, the RFID reader transmits the command by an ASK modulation method that varies the amplitude of a transmission wave, and receives a response wave reflected by the RFID In some cases, it communicates with the RFID by a spread spectrum method in which a spread code is applied to the transmission wave.

The invention's effect

[0071] According to the present invention, the spread spectrum modulation method can be applied as it is to an existing RFID that is low in power consumption, small and inexpensive, so that a complex circuit is newly provided in the RFID or the power consumption of the RFID The communication distance between the RFID reader and RFID can be increased without increasing the communication.

Brief Description of Drawings

[0072] [Fig.1] Diagram showing the state of the transmitted wave and the response wave (reflected wave) that can be considered when the interrogator reader reads the RFID responder

[Figure 2] Diagram showing RFID reading sequence in the RFID system

[Fig.3] Diagram showing reader transmission and reception, RFID reception and response operations

[Figure 4] Configuration diagram showing the basic configuration of the reader used in the RFID system

[Figure 5] Configuration diagram showing the basic configuration of RFID used in the RFID system

[Figure 6] Configuration diagram showing the basic configuration of a clock recovery type RFID used in an RFID system

[Figure 7] Explanation of operation of the modulation SW unit when the amplitude of the carrier wave entering the RFID is varied [Figure 8] Explanation of operation of the modulation SW unit when the phase of the carrier wave entering the RFID is changed

FIG. 9 is a configuration diagram showing a configuration of a reader in the RFID system according to one embodiment of the present invention.

[Fig. 10] Fig. 10A is a waveform diagram showing the RF transmission waveform of the ASK modulated wave used in the bandwidth of 1 MHz, and Fig. 10B shows the empirical curve of the RF transmission wave of the ASK modulated wave used in the bandwidth of 1 MHz. Fig. 10C is a waveform diagram showing how a 100kbps ASK modulated wave is used in the 1MHz band.

[Fig. 11] Fig. 11A is a waveform diagram showing the RF transmission waveform of the ASK modulation wave used in the band of 0.7 MHz, and Fig. 11B is the RF transmission wave of the ASK modulation wave used in the band of 0.7 MHz. Waveform diagram showing the detection waveform obtained by detecting the envelope, Fig. 11C is a waveform diagram showing the use of a 100kbps ASK modulated wave in the band 0.7MHz

[Fig.12] Waveform diagram showing the use of 800kbps ASK modulated wave at 1MHz band [Fig.13] Fig.13A shows that Reader A, Reader B, and Reader C use different bands. Fig. 13B shows a communication method in which Reader A, Reader B, and Reader C perform spread spectrum in the transmission and response reception periods across three bands, and increase the spreading factor by combining multiple bands into one. Illustration of

FIG. 14 is a block diagram showing the configuration of the mobile object identification device described in Patent Document 1.

FIG. 15 is a block diagram showing a configuration of a mobile unit identification communication system described in Patent Document 2.

FIG. 16 is a block diagram showing the configuration of the transbonder described in Patent Document 3.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same reference numerals are given to components having the same configuration or function and corresponding parts, and the description thereof will not be repeated.

First, an RFID reading method in the RFID system according to an embodiment of the present invention will be described.

[0075] FIG. 1 is a diagram showing a situation of a transmission wave and a response wave (reflected wave) that can be considered when a reader that is an interrogator reads RFID that is a responder. As shown in FIG. 1, the path of the transmission wave transmitted from the reader 100 to the RFID 200 is as follows:

There are three main cases:

(1) When the transmission wave 101 of the reader 100 is reflected perpendicularly to the wall (or obstacle) 300, the environment reflected wave 301 containing no information returns to the reader 100 as it is.

(2) When the transmission wave 101 transmitted from the reader 100 reaches the RFID 200 directly,

A response wave 201 of RFID 200 is returned directly to the reader 100.

[0079] (3) When the transmission wave 101 transmitted from the reader 100 is reflected on the wall (or obstacle) 300 and reaches the RFID 200 as the environment reflection transmission wave 302, the response wave 201 from the RFID 200 Is reflected on the wall (or obstacle) 300 and becomes the environment reflection response wave 202. 10

Return to 0.

Here, the RFID 200 reflects the transmission wave 101 from the reader 100 and responds to the reader 100.

When returning as 201 or the environment reflection response wave 202, the data (tag data) in the built-in memory is modulated.

[0081] The reader 100 responds to the response wave 201 from the RFID 200, which is the environment reflected wave 301 returned from the reflected signal on the wall (or obstacle) 300 depending on the presence or absence of modulation of the returned signal. Or it distinguishes whether it is the environmental reflection response wave 202. FIG.

That is, if the received signal is not modulated, the reader 100 determines that the reflected wave 301 is reflected from the wall (or obstacle) 300 and returns to the RFI D200 if modulated. Response wave 201 or environment reflection response wave 202.

In this manner, the reader 100 reads the response wave 201 or the environment reflection response wave 202 from the RFID 200.

FIG. 2 is a diagram showing an RFID reading sequence in the RFID system. In FIG. 2, the reading operation of the RFID 200 by the reader 100 is divided into three periods on the vertical time axis: a CW transmission period, a command transmission period, a transmission and a response reception period.

[0085] First, in the CW transmission period, the reader 100 transmits a carrier wave CW (Carrier Wave). RFID200 receives the carrier wave CW and receives the received carrier wave CW. Starts operation as an electromotive force and transitions to a command reception state.

[0086] Next, in the command transmission period, the reader 100 modulates the transmission wave and transmits the command. When reader 100 sends a command, RFID 200 identifies the received command and determines whether it should respond and what data it should respond to.

[0087] Finally, in the transmission and response reception period, the reader 100 transmits the carrier wave CW. When the RFID 200 that has received the carrier wave CW determines that it should respond in the command transmission period, it modulates the carrier wave CW transmitted from the reader 100 and reflects the response wave carrying data (response information). The reader 100 receives the response wave reflected from the RFID 200 and recognizes (identifies) the presence of the RFID 200.

[0088] FIG. 3 is a diagram showing operations of reader transmission and reception and RFID reception and response. Figure

As shown in Fig. 3, the operations of the transmission and reception of the reader 100 and the reception and response of the RFID 200 are as follows. It is divided into three periods.

In FIG. 3, in the CW transmission period, the RFID 200 always receives the carrier wave CW transmitted by the reader 100 only by the reader 100 transmitting the carrier wave CW.

[0090] In the command transmission period, the reader 100 emits a transmission wave, and the RFID 200

Receiving 0 transmission wave and analyzing the command.

[0091] In the transmission and response reception period, the reader 100 transmits a carrier wave CW during the transmission period, and if the response wave modulated by the RFID 200 is reflected, the reader 100 reception circuit can read the response reception period. Read the response wave (reflected wave) of RFID200.

Here, the RFID 200 reflects the response wave by changing the phase (1, 0) of the transmission wave received from the reader 100 that is not a radio device.

In addition, the RFID 200 converts a part of the received wave received from the reader 100 into an electromotive force in all the three periods described above.

In addition, in RFID 200, a modulation circuit that modulates a reflected response wave operates only during transmission and response reception periods.

[0095] In the reader 100, the demodulation circuit of the response wave reflected from the RFID 200 is in the command reception period. Operate.

[0096] The CW transmission period and the command transmission period are one-way communication distances from the reader 100 to the RFID 200. However, the transmission and response reception periods require a communication distance between the reader 100 and the RFID 200. It is.

Next, a basic configuration of the reader 100 that can be applied to the RFID system of this example will be described. FIG. 4 is a configuration diagram showing a basic configuration of a reader used in the RFID system. The RFID 200 used in this RFID system may be either an active type or a passive type, but here, a passive wave that operates by receiving an electromotive force from a received wave by receiving a transmitted wave transmitted from the reader 100 is used. Type IC tag.

[0098] As described above, such a passive RFID 200 is required to have a simple configuration with as low power consumption as possible.

[0099] Therefore, in this RFID system, the reader 100 can perform ASK modulation so that the transmission wave transmitted by the reader 100 can be demodulated by the RFID 200 performing envelope detection, and a local oscillator is not required for the RFID 200. The command is transmitted using (a modulation mode for modulating the amplitude).

[0100] In this RFID system, the response wave (modulated wave) reflected by the RFID 200 toward the reader 100 is subjected to PSK (Phase Shift Keying) modulation, in which the phase of the received wave is inverted by an impedance switching switch, or The ASK modulation that can change the amplitude with the signal ON / OFF switch makes the RFID200 modulation circuit smaller and simpler.

[0101] When reading the response of RFID200 force, the reader 100 switches between carrier wave CW and ASK modulation in time.

[0102] For this purpose, as shown in FIG. 4, the reader 100 first selects one of transmission data and a fixed value by switching the switch SW.

Here, when the switch SW is switched to select a fixed value, the carrier wave CW is output because the amplitude modulation shows the same value “1”.

On the other hand, when the switch SW is switched to select transmission data (command), the (1, 0) value of the command is ASK modulated by the ASK modulation unit 401 and output.

[0105] Next, the reader 100 transmits the transmission data or fixed data ASK modulated by the ASK modulation section 401. A band-off is performed on the data by the roll-off filter 402 to suppress unnecessary frequencies.

[0106] Then, the reader 100 uses the carrier wave (carrier wave CW) output from the oscillator 403 as the AS.

The K-modulated transmission data or fixed data is orthogonally modulated by the quadrature modulator 404 into the RF frequency band and output (RF output).

[0107] As described above, the transmission data input to the ASK modulation unit 401 of the reader 100 is configured with a value of (1, 0), and when a fixed value is input to the ASK modulation unit 401, an unmodulated carrier It becomes Cave CW.

Therefore, in the CW transmission period and the transmission and response reception period, a fixed value is selected by the switch SW and a fixed value “1” is input to the ASK modulation unit 401.

In the command transmission period, transmission data is selected by the switch SW, and transmission data that is a command to the RFID 200 is input to the ASK modulation unit 401.

[0110] The control of the switch SW in the three periods shown in FIG. 2 and FIG.

05 Force S.

[0111] When the frequency of the radio wave transmitted by the reader 100 is changed, the frequency of the carrier wave output by the oscillator 403 is changed.

[0112] Here, since the frequency output from the reader 100 and the frequency returned from the RFID 200 to the reader 100 are exactly the same frequency, the demodulation unit of the reader 100 performs quadrature demodulation on the same frequency so that the RFID 200 Data (tag data) is extracted from the reflected response wave.

That is, in the transmission and response reception period, the RF input, which is a response wave reflected from the RFID 200, is quadrature demodulated by the quadrature demodulator 406 with the carrier wave output from the oscillator 403 and reflected from the RFID 200 through the roll-off filter 407. The tag data is recovered from the response wave 201.

[0114] By the way, when a plurality of other readers exist within the reach of the transmission wave 101 of the reader 100 and each reader is used at the same time, the transmission waves of the readers interfere with each other. The reception performance of the reader 100 may deteriorate.

Therefore, as a countermeasure against this, the reader 100 of this example performs control to change the frequency of the carrier wave to which the modulation scheme control unit 405 outputs the oscillator 403. Next, the configuration of RFID 100 that can be applied in the RFID system described above will be described. FIG. 5 is a configuration diagram showing a basic configuration of RFID used in the RFID system.

As shown in FIG. 5, the RFID 200 includes a power regeneration circuit 510, an MPU (Micro Processing Unit) 520, a modulation SW unit 530, an oscillator 540, a memory 550, and the like.

[0118] The MPU 520 includes a modulation / demodulation LSI, and includes a demodulation unit 521, a determination unit 522, and a modulation unit 523.

In FIG. 5, RFID 200 first receives a transmission wave transmitted from reader 100 shown in FIG.

[0120] The received wave received by the antenna 560 includes the power regeneration circuit 510, the MPU 520, and the modulation SW.

Each is distributed to 530.

[0121] The power regeneration circuit 510 rectifies the distributed received wave with a rectifier circuit (not shown) to generate RFID2

Generate electromotive force to operate 00.

[0122] The electromotive force generated by the power regeneration circuit 510 includes the MPU 520, the oscillator 540, and the memory 5

50 is supplied as a power source.

[0123] The oscillator 540 serves as an operation clock of the MPU 520, and is used to demodulate a command placed on the received wave and create a modulation rate of the response wave reflected by the RFID 200.

[0124] The demodulation unit 521 of the MPU 520 performs envelope detection of the received wave during the command transmission period (see FIG. 3), and demodulates the command that is placed on the received wave.

[0125] The semi-IJ fixed unit 522 of the MPU 520 determines whether to respond to the transmission and response reception period (see FIG. 3) according to the command demodulated by the demodulation unit 521, and whether to reflect the response wave. Is determined.

Here, when a response of tag data is specified from the reader 100 to the RFID 200 by the command demodulated by the demodulator 521, the tag data stored in the memory 550 is stored in the MPU 510. Read by modulation section 523.

[0127] The modulation unit 523 of the MPU 510 controls the modulation SW unit 530 according to the tag data read from the memory 550, and thereby modulates the response wave reflected by the RFID 200.

[0128] The response wave modulated in this way is radiated toward the reader 100 by the antenna 560. It is.

[0129] In this way, when the RFID 200 receives the carrier wave CW of the reader 100 power and the power is turned on, the demodulation circuit of the demodulator 521 operates. Therefore, when a command comes from the reader 100, the demodulator 521 Demodulation is performed.

[0130] Next, when the determination unit 522 can determine whether or not to respond, the modulation switch of the modulation SW (switch) unit 530 is turned ON / OFF according to the memory 550 held inside the modulation unit 523.

The RFID 200 reflects the received radio wave (transmitted wave from the reader 100) as a response wave by turning on the modulation switch of the modulation SW unit 530 as described above.

[0132] If the command power determination unit 522 demodulated by the demodulation unit 521 determines that the command is not a command addressed to itself, the RFID 200 ignores the instruction of the demodulated command and stands by.

FIG. 6 is a configuration diagram showing a basic configuration of a clock recovery type RFID used in the RFID system.

As shown in FIG. 6, the clock recovery type RFID 200 includes a clock extraction unit 610 that extracts the received wave clock received by the antenna 560.

[0135] Since the received wave of the RFID 200 is ASK modulated, the carrier frequency is the same regardless of the modulation.

That is, in the RFID 200, since the three frequencies shown in FIG. 3 have the same frequency, clock extraction and clock recovery can be performed from the received wave received by the antenna 560.

Therefore, in this clock regeneration type RFID 200, the modulation rate can be operated with the clock accuracy of the reader 100.

[0138] As described above, the RFID 200 shown in Fig. 5 demodulates the incoming radio wave with the clock that it has inside.

On the other hand, the RFID 200 shown in FIG. 6 extracts the clock from the strong electric wave that the clock has, and regenerates the extracted clock to perform modulation and demodulation.

[0140] Here, RFID200 shown in Fig. 5 responds with the internal clock.

Since it is F, it becomes the modulation accuracy with the clock accuracy that RFID200 has. [0141] On the other hand, the RFID 200 shown in Fig. 6 reproduces the frequency of the incoming radio wave, so it can be modulated ON / OFF in synchronization with the clock on the reader 100 side, and the modulated wave that responds to the frequency. Can be synchronized.

Next, the operation of the modulation SW unit 530 of the RFID 200 will be described. FIG. 7 is an explanatory diagram of the operation of the modulation SW unit when the amplitude of the carrier wave entering the RFID is varied. FIG. 8 is an explanatory diagram of the operation of the modulation SW unit when the phase of the carrier wave entering the RFID is changed.

[0143] During the response period of RFID200, the received wave is PSK (or ASK) modulated based on the clock

[0144] Here, when the carrier wave that has entered RFID 200 is ASK-modulated and transmitted,

As shown in Fig. 7, based on the internal clock and transmission data, the amplitude of the received wave is modulated by the binary value of lZO and the response wave is reflected.

That is, in this case, in FIG. 7, the data (tag data) composed of (1, 0, 1,...) Pulses held in the memory 550 with respect to the incoming carrier wave in FIG. In response, the modulation switch 701 is turned ON / OFF.

[0146] When modulation switch 701 is turned ON and shorted to ground, the amplitude of the carrier wave becomes 0, and the amplitude of the reflected response wave momentarily shrinks.

[0147] When modulation switch 701 is turned OFF, the short circuit does not occur and the incoming carrier is snored as it is.

[0148] As described above, the RFID 200 used in the present example outputs (reflects) a response wave carrying the tag data held in the memory 550 by modulating the carrier wave by turning ON / OFF the modulation switch 701. To do.

[0149] On the other hand, when the carrier wave that has entered RFID 200 is modulated and transmitted by PSK modulation, the phase of the received wave is inverted / non-inverted based on the internal clock and transmission data as shown in Fig. 8. Modulates with a binary value and reflects the response wave.

In other words, in this case, in FIG. 8, the modulation switch 801 is turned ON / OFF, and the phase of the carrier wave is inverted by 180 degrees depending on whether the incoming radio wave is terminated or opened. Is output (reflected). [0151] Here, when modulation switch 801 is ON, the phase of the carrier wave is inverted by 180 degrees, and the response wave is reflected in the opposite phase.

[0152] As described above, the RFID 200 used in this example turns ON / OF the modulation switch 701 or 801).

By simply F, the carrier wave can be easily modulated and the response wave carrying the tag data held in the memory 550 can be output (reflected), which can be realized with a simple and inexpensive configuration.

By the way, in the RFID system using the reader 100 and the RFID 200 as described above, when the reader 100 and the RFID 200 are arranged to communicate with each other over a long distance, when the reader 100 reads the RFID 2000, the reader 100 Even if the command transmission wave transmitted from the RFID 200 reaches the RFID 200, the response wave from the RFID 200 may not reach the reader 100 because the response wave reflected by the RFID 200 is weak.

[0154] As a communication method for extending the communication distance between the reader 100 and the RFID 200, as described above, it is effective to multiply the transmission wave of the reader 100 by the spread code and perform spread spectrum modulation on the transmission wave.

However, in such a communication method, since the transmission wave transmitted from the reader 100 is subjected to spectral spread modulation, the RFID 200 cannot recognize the command transmitted from the reader 100.

[0156] For this reason, in this communication method, a despreading demodulation circuit for recognizing a command of 100 readers and determining whether to respond according to the command instruction is provided inside the RFID 200, and the RFID 200 is spread spectrum. Must be compatible with the modulation method

[0157] However, since the RFID 200 having a despreading demodulation circuit in the interior also requires detection of a spreading code, the circuit scale of the extra-spread spreading signal demodulation circuit becomes large and complicated, and power consumption also increases.

[0158] Further, since the passive RFID 200 does not include a battery, it is difficult to secure an electromotive force that can stably drive the passive RFID 200 even if it is provided with a despreading demodulation circuit.

Therefore, in the RFID system using the spectrum spread modulation method, as shown in FIGS. 7 and 8, a modulation response can be made only by turning ON / OFF the modulation switch 701 or 801). Compared with RFID200 with a simple configuration using ASK (or PSK) modulation, RFID200 is less feasible.

[0160] In addition, with RFID 200 that performs clock extraction, it is difficult to correctly extract the clock with a spread spectrum signal power.

[0161] Further, since the spectrum-spread signal cannot obtain a stable detection potential with respect to the time axis, the conversion efficiency of the electromotive force of the power regeneration circuit 510 of the RFID 200 is deteriorated.

[0162] For this reason, in the RFID system using the spectrum spread spectrum modulation method, Figs.

There is a problem that it cannot be directly applied to the RFID 200 having a simple and inexpensive configuration as shown in FIG.

[0163] By the way, in the current RFID system, the communication distance with the reader 100 does not increase due to insufficient electromotive force of the RFID 200. Therefore, it is generally better to increase the strength of the response wave of the RFID 200 than to the R FID 200. Studies are underway on how strong transmission waves can be transmitted.

[0164] However, from the perspective of the future, when the chip of the MPU520 that operates at a low potential is developed due to the advancement of RFID device technology, the problem is not the problem of the communication distance between the reader 100 and the RFID. The problem of the complexity of the RFID200 circuit and the increase in power consumption due to the use of the external spread modulation system becomes dominant.

[0165] For example, in the case of an active RFID, when the response wave is amplified, it becomes a radio device. In addition, in the case of a semi-passive RFID that operates the MPU520 with a built-in battery, the complexity of the circuit and the increase in power consumption are important issues.

[0166] The semi-passive RFID uses the power regeneration circuit 510 shown in FIGS. 5 and 6 with another power source that is not a received wave from the reader 100. As this power source, for example, a lithium battery can be used. A self-power generation type battery such as a small battery or a solar battery is conceivable.

[0167] Therefore, in the RFID system according to the embodiment of the present invention, the command to the RFID 200 is sent by the ASK method that can be realized on a small circuit scale, and only when the reader 100 reads the reflected response wave having a long communication distance. Control the modulation method to obtain the effect of spread spectrum.

[0168] Thus, in the RFID system of this example, the RFID 200 force is shown in Figs. While maintaining such a compact and low power consumption configuration, the same command control as before can be performed and the communication distance between the reader 100 and the RFID 200 can be extended.

[0169] Further, in the RFID system of this example, the reader 100 is provided with CW addition means.

Even if the spectrum is spread, the reader 100 can output a stable transmission wave for power supply to the RFID 200 during the communication period, and can output a transmission wave from which the clock can be extracted.

[0170] Also, in the RFID system of this example, in order to obtain a high spreading factor of the transmission wave of the reader 100, only when the reflected response wave of the RFID 200 is read, it is spread over the plurality of usable carrier frequency bands. I have to.

As described above, in the RFID system of this example, the above-described problem can be solved only by the transmission wave of the reader 100, and the RFID 200 has the ASK reception, P shown in FIG. 5 and FIG.

It can be configured to communicate with a SK reflection type circuit.

Next, the configuration of the reader used in the RFID system of this example will be described. FIG. 9 is a configuration diagram showing the configuration of the reader in the RFID system according to the embodiment of the present invention.

As shown in FIG. 9, the reader 900 of this example is similar to the reader 100 shown in FIG. 4. The ASK modulation unit 401, the roll-off filters 402 and 407, the oscillator 403, the quadrature modulator 404, the modulation scheme control, and the like. A control unit 405 and an orthogonal demodulation unit 406 are provided.

[0174] Also, the reader 900 of this example includes a spectrum spreader 901, a despreader 902, and a CW adder 903.

, And attenuator (ATT) 904.

In FIG. 9, ASK modulation section 401 ASK modulates transmission data or fixed data selected by switching SW 1 and sends a control command of RFID 200 as a transmission wave

[0176] Spectrum spreader 901 is a long-period spread code selected by switching switch SW2.

(Scramble code) is multiplied by the transmission data or fixed data modulated by ASK modulation section 401.

[0177] The roll-off filter 402 is ASK-modulated by the ASK modulator 401, and is transmitted data or a fixed data obtained by multiplying the spectrum spreader 901 by a long-period spread code (scramble code). The band is limited to suppress unnecessary frequencies.

[0178] Quadrature modulator 404 orthogonally modulates transmission data or fixed data ASK-modulated with the carrier wave output from oscillator 403 into the RF frequency band and outputs the result.

[0179] The CW adder 903 adds the carrier wave (carrier wave CW) output from the oscillator 403 to the transmission wave (RF output) at an arbitrary power ratio attenuated by the attenuator (ATT) 904.

[0180] The quadrature demodulator 406 performs quadrature demodulation on the RF input, which is the response wave 201 reflected from the RFID 200, with the carrier wave output from the oscillator 403.

Ronolev Finnoletter 407 performs band limitation for suppressing unnecessary frequency with respect to the reception data demodulated by quadrature demodulator 406.

[0182] The despreader 902 despreads the reception data demodulated by the quadrature demodulator 406 and reads the tag data of the RFID 200.

[0183] The reader 900 of this example extends the receivable distance of the reflected response wave of the RFID 200 by transmitting the transmission wave to the RFID 200 by changing the modulation method adaptively in the command transmission period, transmission and response reception period. .

[0184] In the reader 900 of this example, first, in the CW transmission period described above, the ASK modulation data is always a fixed value, the spreading code is always a fixed value, and the addition of the carrier wave (carrier wave CW) is turned off. Therefore, it is possible to transmit the same carrier wave CW as the reader 100 shown in FIG. In other words, in the CW transmission period, spreading is not performed by setting the spreading code to a fixed value.

[0185] Next, in the operation of the command transmission period, ASK modulation data is always transmitted data (command data), spreading code is always fixed, and carrier wave (carrier wave CW) addition is turned off. ASK modulation is performed in the same way as the reader 100 shown.

Thus, in the reader 900 of this example, the command reaches the RFID 200 placed at the same distance as the RFID system of the reader 100 shown in FIG. 4, and the RFID of the reader 100 shown in FIG. As with the system, the RFID 200 can recognize commands.

Next, the operation during the transmission and response reception period in the reader 900 of this example will be described. First, consider the case of the self-running clock type RFID 200 shown in FIG. In the transmission and response reception periods in the reader 900 of this example, when obtaining a response wave, the reader 900 spreads the spectrum by applying a spreading code to the transmission wave, and the addition of the carrier wave CW is turned off.

[0189] The RFID 200 modulates the information data of the reader 900 with the PSK (or ASK) information based on the internal clock and reflects it as a response wave.

Here, since the transmission wave of the reader 900 reaches the RFID 200 and reaches the reader 900 as a reflection response wave from the RFID 200, the reader 900 reciprocates between the reader 900 and the RFID 200. Therefore, the transmission wave of the reader 900 causes a round-trip propagation loss between transmission and reception.

[0191] When a propagation loss occurs in the transmission wave of the reader 900, if the signal-to-interference and noise ratio (SIR) falls below a certain value, the error rate for correct information data increases and demodulation is impossible.

[0192] The SIR (signal-to-interference amount ratio) value at which this demodulation cannot be performed is smaller in the spectrum spread ASK modulation than in the case of only the ASK modulation. This is because interference and noise uncorrelated with the spreading code can be reduced by the spreading gain by despreading.

Therefore, in the RFID system of this example, the communication distance of the reflected response wave is extended by using spread spectrum for modulation and demodulation.

[0194] By the way, when performing extra-spread spreading as described above, a force that requires a wider bandwidth than the generally used bandwidth is described below in the RFID system of this example. As described above, the spreading gain can be obtained even when the bandwidth used is the same.

[0195] FIG. 10A is a waveform diagram showing an RF transmission waveform of an ASK modulated wave used in a band of 1 MHz. FIG. 10B is a waveform diagram showing a detection waveform obtained by detecting the envelope of the RF transmission wave of the ASK modulation wave used in the band of 1 MHz.

When the reader 900 sends a command as shown in FIG. 10A, the RFID 200 detects the ASK modulated wave and takes out the envelope as shown in FIG. 10B.

[0197] At this time, if the rise of (1, 0) in amplitude modulation is not fast enough, the determination unit 522 of the RFID 200 may erroneously determine (1, 0).

That is, in the RFID system, when the reader 900 sends a command to the RFID 200, there is a rule that the edge of (1, 0) in amplitude modulation must be sharp.

[0199] When the edge of (1, 0) in the amplitude modulation is sharpened in this way, the spectrum shown in Fig. 10C is obtained. As shown in the waveform, even though it is moving at 100kbps (100K chip rate), it occupies about 10 times the bandwidth of 1MHz. This is because the rising edge of (1, 0) in amplitude modulation must be accelerated as shown in FIG. 10B.

[0200] In this way, by making the switching edge of the (1, 0) data in the amplitude modulation steep, the probability of erroneous data determination by the determination unit 522 force ΐ, 0) of the RFID 200 is reduced.

[0201] In addition, if the switching edge of the (1, 0) data in the amplitude modulation is sharpened, the frequency use bandwidth is widened.

[0202] FIG. 10C is a waveform diagram showing a state where a 100 kbps ASK modulated wave is used in a band of 1 MHz.

[0203] Here, as shown in FIG. 11A, if the (1, 0) edge of the RF transmission wave of the ASK modulated wave is dulled and transmitted, as shown in FIG. Thus, the bandwidth can be narrowed, and the bandwidth with the spectrum can be suppressed to 70%.

[0204] However, if a 100 kbps ASK modulated wave is used with a bandwidth of 0.7 MHz and the frequency bandwidth is narrowed, the rise of the ASK modulated waveform is delayed, so the detected waveform is (1 , 0) cannot be obtained, and the RFID 200 does not move sufficiently, making it difficult for the determination unit 522 to determine (1, 0).

[0205] Therefore, actually, even when the reader 900 transmits an ASK modulated wave of 100 kbps, a band of about 1 MHz is required.

[0206] As described above, the ASK modulation wave for the RFID 200 that performs envelope detection must use about 10 times the bandwidth of the modulation rate.

[0207] On the other hand, when performing spread spectrum, the transmission wave does not need to be ASK modulated during the transmission and response reception period, and the RFID 200 need not even perform envelope detection.

[0208] At this time, as shown in FIG. 12, if the spread code is used to spread the spectrum 8 times, the rate is increased to 800 kbps, and the band is limited by the roll-off filter 402, the transmission is performed in the 1 MHz band. It is possible.

[0209] In other words, when applying spread spectrum in the RFID system of this example, it seems necessary to perform spread of 8 times to 800K, which is 8 times of ASK of 100k bps. [0210] However, even if the band for 800K is used at this time, if it has a frequency band almost the same as that used for 1 MHz at 100kbps in ASK, it is 8 Double spectral diffusion.

[0211] Therefore, in the RFID system of this example, even if the reception sensitivity of 18 db is increased by applying 8 times spread spectrum as described above, transmission can be performed in the same band, and an extra band is used. There is no problem.

[0212] In this way, in the RFID system of this example, by using the spread spectrum modulation method as described above, spread spectrum communication can be performed without widening the frequency bandwidth to be used. Can extend the communication distance between RFID and RFID200.

[0213] In the transmission and response reception period in the case of the clock recovery (synchronous clock) type RFID 200 shown in FIG. 6, as in the case of the RFID 200 shown in FIG. By performing spectrum spread that is resistant to interference and noise, the communication distance between the reader 900 and the RFID 200 can be extended.

[0214] Here, RFID 200 modulates the reflected response wave based on the internal clock frequency-synchronized with the transmission wave of reader 900, but the clock may not be synchronized with the spread spectrum transmission wave.

[0215] In such a case, the reader 900 adds the carrier wave CW to the transmission wave at a constant ratio by the CW adder 903, so that the RFID 200 transmits a signal that facilitates clock synchronization.

[0216] In this way, adding the carrier wave CW to the transmission wave at a constant ratio by the CW adder 903 is equivalent to simply transmitting the PAPR (peak The effect of reducing the ratio of the averaged power to the power is S. Stable power supply to the power supply circuit of the RFID 200 is possible.

Note that the carrier wave CW added to the transmission wave by the CW power calculator 903 becomes an interference component when demodulating the spectrum-spread signal, but it is inversely expanded in the receiving circuit of the reader 900. It is removed according to the spreading factor of the despreader 902 which is a spreading circuit.

[0218] Further, in the RFID system of this example, since transmission and reception are performed by the same reader 900, an arithmetic circuit that cancels out the carrier wave CW that becomes an interference component at the reception unit is provided. It can also be provided and removed.

[0219] In this way, in the RFID system of this example, by using the reader 900 shown in FIG. 9 and the RFID 200 shown in FIG. 5 or FIG. 6, an ASK-modulated command is received, and the reflection response period. In RFID200 that reflects and modulates PSK (or ASK) information, it can be applied to RFID200 receiver and transmitter without being aware of the spread spectrum modulation method.

Therefore, in the RFID system of this example, the existing RFID 200 with low power consumption and small size can be used as they are, and the communication distance with the reader 900 can be extended.

[0221] Furthermore, in the RFID system of this example, the CW adder 903 adds the carrier wave CW to the transmission wave of the reader 900, so that the clock reproduction type RFID 200 that performs clock extraction as shown in Fig. 6 also receives it. The clock can be correctly extracted from the signal.

Even at 10, a stable detection potential can be obtained with respect to the time axis.

[0222] Next, in the case of the above-described spread spectrum, the CDMA (Code Division Multiple Access) method is used between multiple readers as a method of utilizing transmission capability of other readers as an interference wave and taking advantage of the anti-interference capability. An RFID system using the above will be described.

[0223] As a reading method of RFID200 in the RFID system, the frequency is divided into several bands so that the readers do not interfere with each other, and separate bands are used between the readers. The frequency division method is used.

[0224] On the other hand, in the RFID system, the spread gain is increased by the above-described spread spectrum.

The code recovery capability against interference increases.

[0225] Therefore, in the RFID system of this example, the command transmission period uses a conventional frequency division method that switches the carrier frequency, and the reflection response period uses a CD that uses the entire band.

Use the MA method.

[0226] FIG. 13A is a diagram showing a state in which reader A, reader B, and reader C use different bands. Fig. 13B shows a communication method in which reader A, reader B, and reader C perform spread spectrum spreading over three bands during transmission and response reception periods, and increase the spreading factor by combining multiple bands into one. It is explanatory drawing of.

[0227] In the spread spectrum method shown in Fig. 13B, the spreading factor of the transmitted wave is increased three times. Therefore, the communication distance between the reader 900 and the RFID 200 can be further extended.

[0228] Also, in the spread spectrum system that spreads the transmission wave in the transmission and response reception periods, spread codes that are orthogonal between the three readers A, B, and C are used.

[0229] In an RFID system employing such a CDMA system, even when three readers A, B, and C are communicating simultaneously, it is possible to separate the transmission waves from each other during demodulation.

Therefore, in such an RFID system using the CDMA system, the communication distance between the reader 900 and the RFID 200 can be increased by further increasing the spreading factor of the transmission wave.

[0231] In other words, when communication is performed using different frequencies (bands) for Reader A, Reader B, and Reader C, applying spread spectrum as is is shown in Fig. 13A. It is possible to further extend the communication distance by using all the bands for one band and increasing the spreading factor by 3 times as shown in Fig. 13B.

[0232] In this way, the command transmission period during which the reader 900 is transmitting commands uses different frequencies, and uses the spreading factor three times at the middle frequency only during the period when the RFID 200 reception response is being viewed. . Thereby, the spreading factor of the transmission wave of the reader 900 can be increased and used.

[0233] Here, a long-term scramble code (spreading code) is orthogonalized by reader A, reader B, and reader C (if the code system 歹 is used, the signals A, B, and C are multiplexed on the same frequency. Even if they are multiplexed, they can be separated at the demodulation part, so the spreading factor can be increased by applying the CDMA method.

[0234] The RFID system of this example is similar to a system that reads a QR code (two-dimensional barcode) with a camera-equipped mobile phone and displays a homepage at a predetermined address from the read code information. The RFID200 reader 900 is installed in the product, and RFID tags such as RFID tags attached to retail store products are read by the mobile phone reader 900, so that the manufacturer's list and price of the product can be read from the tag data information. Is considered.

[0235] As a result, in the RFID system of this example, the RFID (tag) 200 attached to the product or the like can be read with the mobile phone reader 900 and enjoyed using the RFID 200 tag data information in various ways. Become.

[0236] How to install the reader 900 in a mobile phone, assuming such applications However, since the reader 900 in the RFID system of this example can be realized on a small circuit scale that transmits the command to the RFID 200 by the ASK method, the reader 900 can be easily installed in the mobile phone. .

[0237] In the case of an RFI D system that uses CDMA (Code Division Multiple Access) between multiple readers, a new CDMA communication can be achieved by installing the reader 900 in a CDMA mobile phone. An RFID system can be constructed without adding means.

[0238] As described above, in the RFID system of this example, the RFID 900 receives a command by ASK modulation in the command transmission period in which the reader 900 transmits a command.

[0239] Therefore, in the RFID system of this example, it is possible to receive the command transmitted by the reader 900 with the RFID 200 formed of a simple and inexpensive small circuit as shown in FIG. 5 or FIG. .

[0240] Further, in the RFID system of this example, the spectrum spread is performed only when the reader 900 reads the response wave of the RFID 200, that is, during the transmission and reception response periods in which the communication distance is a reciprocal distance. Let's go.

[0241] As described above, in the RFID system of this example, when the reader 900 sends a command, the RFID 200 receives the command by ASK modulation, and the spread spectrum modulation is performed only when the reader 900 reads the response wave of the RFID 200. The communication distance between the reader 900 and the RFID 200 is increased.

[0242] That is, in the RFID system of this example, when the switch SW1 of the reader 900 is turned ON / OFF during the CW transmission period and the command transmission period, the switch SW2 of the reader 900 is set to a fixed value (diffusion OFF). Switch to N side.

[0243] Thus, the reader 900 can transmit the carrier wave CW and the command without performing the spread spectrum, similarly to the case of the reader 100 shown in FIG.

[0244] Then, the reader 900 sets the switch SW2 to the side where the long-term spreading code (scramble code) is 0N when the carrier wave CW is transmitted only during the transmission and response reception period for reading the response wave of the RFID200. Switch. [0245] This allows the reader 900 to emit a spread spectrum signal.

[0246] When the reader 900 radiates a spectrum spread signal in this way, the RFID 200 responds to the received radio wave (transmitted wave from the reader 900) by turning on and off the modulation switch of the modulation SW unit 530. Reflects as a wave.

[0247] Here, the RFID 200 in the RFID system of the present example is spread spectrum by turning on / off the modulation switch of the modulation SW unit 530 according to the data of the memory 550 with an internal timer. Since only the reflected signal is reflected, the transmission and response reception period can reflect and respond to any signal, especially without the need for carrier wave CW.

[0248] In other words, in the RFID system of this example, if the reader 900 spreads the spectrum to the command, the RFID 200 needs a despreader, but it does not need to read the command. During the period, even if the reader 900 spreads the spectrum, the RFI D200 responds as it is.

[0249] Therefore, the reader 900 in the RFID system of this example switches the switch SW2 to the spectrum spreading side only during the transmission and response reception periods that are the last section, and performs ASK modulation with the modulation switch of the modulation SW section 530 of the RFID200. The signal turned ON / OFF is despread by the despreader 902, and demodulated.

[0250] As described above, in the RFID system of this example, the communication distance between the reader 900 and the RFID 200 is extended by performing spectrum spread only during the reflection response period in which the RFID 200 reflects the response wave. A wide range of RFID 200 can be read without changing the circuit configuration of RFID 200.

[0251] By the way, the RFID 200 can easily take a stable power source as a detection circuit when the electromotive force is generated when the transmission wave of the reader 900 is a carrier wave CW component. In other words, when the transmission wave of the reader 900 is a spectrum-spread signal, the RFID 200 regenerates the power by the power regeneration circuit 510 because the instantaneous power increases and decreases.

[0252] Therefore, the reader 900 in the RFID system of this example adds the carrier wave CW to the transmission wave at a constant ratio by the CW adder 903 so as to output RF.

[0253] In this way, in the reader 900 of this example, the carrier wave is transmitted to the transmission wave by the CW power calculator 903. By adding the wave CW, it is possible to stabilize fluctuations in the detection circuit of RFID200.

[0254] An RFID system according to the first aspect of the present invention includes an RFID having a storage unit storing data, and reading the data stored in the storage unit by wireless communication with the RFID An RFID system comprising: a device, wherein the RFID reader transmits the command by an ASK modulation method that varies an amplitude of a transmission wave when transmitting a command to the RFID; When the response wave reflected by the RFID is received, a configuration is adopted in which the RFID communicates with the RFID by a spread spectrum method in which a spread code is applied to the transmission wave.

[0255] According to this configuration, when the RFID reader transmits a command to the RFID, the command is transmitted without spectrum spread by the ASK modulation method that varies the amplitude of the transmission wave. The command can be recognized with the conventional configuration. When receiving the reflected response wave of the R FID, the RFID reader communicates with the RFID using a spread spectrum system that applies a spread code to the transmitted wave, so the communication distance between the RFID reader and the RFID can be extended. .

[0256] The RFID reader according to the second aspect of the present invention is an RFID reader used in the RFID system of the first aspect, and the amplitude of the transmission wave when transmitting a command to the RFID ASK modulation means for varying the frequency and a spread spectrum means for applying a spread code to the transmission wave when receiving the response wave reflected by the RFID are employed.

[0257] According to this configuration, the amplitude of the transmission wave varies when a command is transmitted to the RFID by the ASK modulation means. This makes it possible for RFID to recognize commands with the conventional configuration. Then, the spread spectrum is applied to the transmission wave when the RFID reflection response wave is received by the spread spectrum means. As a result, the communication distance between the RFID reader and the RFID can be increased only when the reflected response wave of the RFID is received.

[0258] The RFID reader according to the third aspect of the present invention employs a configuration comprising, in the second aspect, a carrier addition means for adding a carrier wave to the transmission wave spectrum spread by the spectrum spreading means. . [0259] According to this configuration, since the carrier wave is added by the carrier wave addition means to the transmission wave that has been spread spectrum by the spread spectrum means, the PAPR (averaged with respect to the peak power) of the transmission wave obtained by converting the total output power to a constant value. This has the effect of reducing the power ratio) and enables stable power supply to the R FID power supply circuit.

[0260] The RFID reader according to the fourth aspect of the present invention is the RFID reader according to the third aspect, wherein the communication period with the RFID is three periods of a carrier transmission period, a command transmission period, a transmission and a response reception period. In the carrier transmission period, a carrier wave is transmitted to the RFID. In the command transmission period, the transmission wave is ASK modulated to the RFID to transmit a command, and in the transmission and response reception period. The operations of the ASK modulation means, the spread spectrum means, and the carrier wave adding means are adaptively controlled so that the transmission wave is spread spectrum by the spread spectrum means when the response wave reflected by the RFID is received. The structure which comprises the modulation system control means to take is taken.

[0261] With this configuration, the modulation scheme control means adaptively controls the operations of the ASK modulation means, the spread spectrum means, and the carrier wave addition means, so the ASK modulation means transmits a command to the RF ID. The amplitude of the transmitted wave is changed. In addition, when the RFID reflection response wave is received, a spread code is applied to the transmission wave by the spectrum spreading means. As a result, the RFID can recognize the command with the conventional configuration, and the communication distance between the RFID reader and the RFID can be increased only when the reflected response wave of RFI D is received.

[0262] The RFID reader according to the fifth aspect of the present invention is the RFID reader according to the second aspect, wherein the spread spectrum means spreads a transmission wave using a spread code orthogonal to a plurality of RFID readers. The transmission frequency used in the transmission and response reception period is the same for the plurality of RFID readers.

[0263] According to this configuration, if each RFID reader uses a code (code sequence) in which long-term scramble codes (spreading codes) are orthogonal to each other, each RFID reader is multiplexed on the same frequency. Even if they are multiplexed, they can be separated at the demodulation part, and the spreading factor can be increased by applying the CDMA system. Industrial applicability

The RFID access method and reading apparatus according to the present invention can extend the communication distance between the RFID reading apparatus and the RFID by directly applying the spread spectrum modulation method to the existing RFID that is low in power consumption and small and inexpensive. It is useful as an RFID system and RFID reader using a spectrum diffusion method as an IC tag reading method.

Claims

The scope of the claims

[1] An R FID system comprising: an RFID having storage means for storing data; and an RFID reader for reading the data stored in the storage means by wireless communication with the RFID,

The RFID reader transmits the command by an ASK modulation method that varies the amplitude of a transmission wave when transmitting a command to the RFID, and transmits the response wave when the response wave reflected by the RFID is received. An RFID system that communicates with the RFID using a spread spectrum method that applies a spreading code to waves.

[2] An RFID reader used in the RFID system according to claim 1,

ASK modulation means for changing the amplitude of a transmission wave when transmitting a command to the RFID,

An RFID reader comprising: a vector spreading means for applying a spreading code to the transmission wave when receiving a response wave reflected by the RFID.

3. The RFID reading apparatus according to claim 2, further comprising a carrier wave adding unit that adds a carrier wave to the transmission wave that has been spread spectrum by the spectrum spreading unit.

[4] The communication period with the RFID is divided into three periods: a carrier transmission period, a command transmission period, a transmission and response reception period,

In the carrier wave transmission period, a carrier wave is transmitted to the RFID. In the command transmission period, the transmission wave is ASK-modulated to the RFID and a command is transmitted. In the transmission and response reception period, the RFID is reflected. When the response wave to be received is received, the operations of the ASK modulation means, the spread spectrum means, and the carrier wave addition means are adaptively performed so that the transmission wave is spread by the spread spectrum means. 4. The RFID reader according to claim 3, further comprising a modulation method control means for controlling.

[5] The spread spectrum means uses a spread spectrum system that spreads a transmission wave using spread codes orthogonal to each other between a plurality of RFID readers,

3. The RFID reader according to claim 2, wherein a frequency of a transmission wave used in the transmission and response reception period is the same in the plurality of R FID readers.