CN101118588A - RFID reader and its system, method and application system - Google Patents

Abstract

The invention relates to the field of radio frequency identification, specifically an RFID reader and its system, method and application system. In order to increase the transmission distance of the existing RFID system, and to overcome the influence of obstructions, the method includes step 1, the reader radio frequency unit of the slave reader is under the control of the slave reader control unit, through at least one antenna and at least one remote transmitter The transponder or its downstream slave reader's transponder radio frequency unit communicates and obtains corresponding information; Step 2, the slave reader's transponder radio frequency unit communicates with the master reader or its upstream slave through the antenna The reader radio frequency units of the readers communicate and transmit said information to the reader radio frequency units of the master reader or its upstream slave readers. The beneficial effect of the invention is that the system has great flexibility, and the structure of the whole system is quite simple and easy to maintain.

Description

RFID reader and its system, method and application system

technical field

The present invention relates to the field of radio frequency identification, in particular to long-distance or application of radio frequency identification technology in a closed box, specifically an RFID reader and its system, method and application system.

Background technique

Radio Frequency Identification (RFID) technology is an automatic identification technology that is paralleled with barcode recognition, optical character recognition, smart cards and biometrics. An RFID transponder transmits a unique identification code, such as an Electronic Product Code (EPC), stored thereon to an RFID reader for item or identity identification.

From the perspective of the working principle of the RFID system, the system generally consists of two parts: a transponder (such as an electronic tag, etc.) and a signal receiver (reader). The following will be explained respectively:

① Transponder

In the RFID system, transponders exist in different forms for different application purposes, and the typical form is a tag (Tag). The label is equivalent to the barcode symbol in barcode technology, which is used to store the information that needs to be identified and transmitted. In addition, unlike the barcode, the label must be able to transmit the stored information automatically or under the action of radio frequency signals. The radio frequency unit of the transponder is used to demodulate and decode the signal of the reader, and encode and modulate the signal sent to the reader. The radio frequency unit also has a simple antenna, which is used to receive, transmit and read signal between devices.

②Signal receiver (reader)

In RFID systems, signal receivers are generally called readers. According to the different types of supported tags and different functions (such as encrypted transmission functions), the complexity of the reader is very different. The basic function of the reader is to provide data interaction with the tag. In addition, the reader also provides quite complex signal state control, parity error checking and correction functions, etc. In addition to storing the information to be transmitted, the label must also contain certain additional information, such as error checking information. Identification data information and additional information are compiled according to a certain frame structure and sent out in a specific order. The reader controls the sending of the data stream by receiving additional information. Once the information arriving at the reader is correctly received and interpreted, the reader decides through a specific algorithm whether it needs the transponder to resend the sent signal, or inform the transponder to stop sending the signal, which is the "command" Response Protocol". Using this protocol, even reading multiple tags in a short time and a small space can effectively prevent information confusion. The radio frequency unit of the reader is used for the information to be sent, after being coded and modulated, it is loaded on a carrier signal of a certain frequency and sent out through the antenna, and demodulates and decodes the received response signal of the transponder , the radio frequency unit also has an antenna for transmitting RF signals to the transponder and receiving signals returned by the transponder.

In practical applications, the power of the RFID system, the shape and relative position of the antenna will affect the transmission and reception of the signal, requiring professionals to design and install the antenna of the system.

According to the energy supply, RFID transponders are divided into passive transponders (Passive Tag) and active transponders (Active Tag). Active transponders have their own power source, typically a battery, or solar or other energy source. Passive transponders do not have corresponding power supply equipment. Instead, they collect radio waves emitted by RFID readers and use them as power sources. Therefore, passive transponders are cheaper than active transponders, and There is a higher scope of application.

When the passive tag enters the magnetic field, if it receives a special radio frequency signal from the reader, it can send out the product information stored in the chip by obtaining the energy of the induced current; or the active tag is supplied by the energy of its transponder Part provides energy to actively transmit a signal of a certain frequency. After the reader reads and decodes the information, it is sent to relevant systems (such as the accounting system of the supermarket, the management system of the warehouse, etc.) for relevant data processing.

RFID passive devices use radio waves as a means of energy supply and communication, and the signal must be within the range allowed by the transponder, usually 10 feet (about 3 meters). This type of tag is suitable for short-range information identification, such as setting passive tags on small commodities such as disposable razors or removable blade packaging boxes.

Generally speaking, RFID transponders are designed to be as small and simple as possible due to the consideration of energy consumption and cost, while passive transponders have small antennas and limited storage space, and can pass receiving Electromagnetic waves give it the energy to transmit data over long enough distances. For passive transponders, such as backscatter connected transponders (after the transponder receives the reader's RF signal, it reflects the signal to the reader at the same frequency, and the reflected signal carries the transmitter The radio frequency signal of the transponder information is for the reader to process and identify), and the interpreted data is also modulated to reflect the electromagnetic waves emitted by the reader, so the effective range is very small. However, transponders for many RFID applications require long-distance operation, and current RFID systems cannot meet such requirements.

In the prior art, the RFID reader and the RFID transponder are mainly changed, for example, the radio frequency power is enhanced, different frequencies are used, and new materials are used, but these methods cannot fundamentally solve the problem of short transmission distance. , and lead to an increase in production costs.

Chinese patent 03824841.7, titled "Method and device for storing and distributing information in radio frequency identification tags", discloses a method and device for storing and distributing information in radio frequency identification tags. RF transceivers for long-range RF communications, and interfaces to support short-range communications with short-range readers over secure links. An RF transceiver can be used to send the ID stored in the tag's memory to a long-range reader, and an interface can be used to send sensitive historical information to a short-range reader over a secure link. Although this solution can provide a relatively long card reading distance, but using a long-distance reader with enhanced transmission power, the cost will rise rapidly with the increase of the signal receiving distance, and the scalability and flexibility of the system are relatively low.

Chinese patent 00813640.8, the title of the invention is "Low-cost long-distance radio frequency identification reading", which discloses a method of printing two large-area areas on the packaging bag and the packaging box with conductive ink, and these two areas are covered by the packaging box or packaging Separated by a non-conductive part of the bag, it acts as an RF antenna, and then a label with an RFID chip is placed across the two conductive ink parts of the RF antenna, actually connecting the antenna part to the RFID On-chip, this results in a product that is easy to implement in terms of probing or reading. Since the area of the antenna is increased by ink printing, the effective range of the antenna is also increased accordingly. Although this scheme can increase the detection distance of the RFID system to a certain extent, it still cannot detect the RF tags in the container or the closed box. detection.

Contents of the invention

In order to solve the above problems, the object of the present invention is to provide an RFID reader, which uses the transponder unit on the device to receive the signal from the master reader, and uses the reader on the device to send the signal to the real transponder , and receive the return information from the real transponder, and return the information stored on the device to the master reader.

In order to solve the above problems, the object of the present invention is to provide a layered RFID system, which can greatly increase the application distance of RFID. tag information in one frame, and transmit the information to the upper-level slave reader or master reader through the transponder unit of the slave reader. This enables the technology of RFID to be applied in a wider range, and the layered RFID structure of the present invention is transparent to existing transponders and systems, and does not require any changes to existing RFID system and structure standards.

In order to solve the above problems, the purpose of the present invention is to provide a long-distance RFID information transmission method, which can effectively increase the information transmission distance between the reader and the real tag through a simple method.

In order to solve the above problems, the object of the present invention is to provide a layered RFID system for scanning tags inside a box, a system for scanning tags when there is an obstacle between the tag and the reader.

An RFID reader comprising,

a readable and writable memory, connected to the control unit, for storing information of at least one transponder;

a reader radio frequency unit, connected to said control unit, for modulating and demodulating radio frequency signals with at least one of its downstream transponders;

It is characterized in that it also includes:

a transponder radio frequency unit, connected to said control unit, for modulating and demodulating radio frequency signals between its upstream reader;

at least one antenna, connected to said transponder radio frequency unit and reader radio frequency unit, for transmitting and receiving signals between its upstream reader or downstream transponder;

Said control unit controls said reader radio frequency unit to collect information of at least one transponder downstream thereof, stores said information in said readable and writable memory, and controls said transponder radio frequency unit to read upstream The device transmits the information.

There are two antennas, one is connected to the radio frequency unit of the transponder, and the other is connected to the radio frequency unit of the reader.

A layered RFID system comprising, a master reader, at least one remote transponder; further comprising:

at least one slave reader, coupled between said master reader and said at least one remote transponder, the reader radio frequency unit of the slave reader collects said at least one remote transponder response via at least one antenna information from the transponder radio frequency unit of the reader or the downstream slave reader, and the transponder radio frequency unit of the slave reader transmits the information to the reader of the master reader or the upstream slave reader via the antenna radio frequency unit.

At least two of the slave readers are hierarchically connected in series between the master reader and the at least one remote transponder, and the radio frequency unit of the transponder of the layer 1 slave reader is connected to the The master reader, the reader radio frequency unit of the layer 1 slave reader is connected to the transponder radio frequency unit of the downstream layer i slave reader through the antenna, and the reader radio frequency unit of the layer i slave reader is connected through the The antenna is connected to the transponder radio frequency unit of its downstream layer n slave reader, the reader radio frequency unit of the layer n slave reader is connected to the remote transponder through the antenna, i is 2 to n positive integer of .

There are two antennas, one is connected to the radio frequency unit of the transponder of the slave reader, and faces the reader radio frequency unit of the master reader or its upstream slave reader; the other is connected to the slave reader reader radio unit and towards the transponder radio unit of the remote transponder or its downstream slave reader.

A method for layered transmission of an RFID system, comprising:

Step 1, the reader radio frequency unit of the slave reader communicates with at least one remote transponder or the transponder radio frequency unit of its downstream slave reader through at least one antenna under the control of the slave reader control unit, and obtain relevant information;

Step 2, the transponder radio frequency unit of the slave reader communicates with the reader radio frequency unit of the master reader or its upstream slave reader through the antenna, and sends the information to the master reader or its upstream reader Transmitted by the reader RF unit of the upstream slave reader.

Before said step 1, a starting step is also included, the transponder radio frequency unit of said slave reader receives the signal of said master reader or the reader radio frequency unit of its upstream slave reader through said antenna, and The signal is sent to the control part of the slave reader to activate the reader radio frequency unit of the slave reader to perform step 1.

In said step 2, said slave reader compresses the collected information of said at least one remote transponder or the transponder radio frequency unit of its downstream slave reader into a payload in one frame, and sends to Transmitted by the reader RF unit of the master reader or its upstream slave readers.

The transponder radio frequency unit of the slave reader is active or passive, and the reader radio frequency unit is active.

There are two antennas, one is connected to the radio frequency unit of the transponder and faces the reader radio frequency unit of the master reader or its upstream slave reader; the other is connected to the radio frequency unit of the reader and faces The transponder radio frequency unit of the remote transponder or its downstream slave reader.

A layered RFID system for scanning transponders located behind a shield, comprising, a master reader, at least one remote transponder, a shield, the at least one remote transponder in the On one side of the shield, the master reader is on the other side of the shield, further comprising,

Also included is a slave reader mounted on the shield with two antennas, antenna 1 on the master reader side of the shield and antenna 2 on the remote transponder side of the shield The transponder radio frequency unit of the slave reader transmits signals with the reader radio frequency unit of the master reader or its upstream slave reader through the antenna 1, and the reader radio frequency unit of the slave reader passes through The antenna 2 transmits signals with the transponder radio frequency unit of the at least one remote transponder or its downstream slave reader; the reader radio frequency unit of the slave reader collects the Information of at least one remote transponder or the transponder radio frequency unit of its downstream slave reader is transmitted via the transponder radio frequency unit of said slave reader and said antenna 1 to said master reader or Reader RF unit of its upstream slave reader.

The beneficial effect of the present invention is that in the existing RFID system, there is no need to replace the existing equipment, only a slave reader with a very simple structure can be added between the existing reader and the tag to increase the communication distance and the expansion and contraction of the system The reliability is great, and the structure of the whole system is quite simple and easy to maintain. And by placing the slave reader in the container, etc., the purpose of identifying the internal label of the container can also be easily realized.

Description of drawings

Fig. 1 is the structure schematic diagram of layered RFID slave reader device of the present invention;

Fig. 2 is a sequence diagram of the method of the present invention;

Fig. 3 is the frame conversion schematic diagram of the present invention increasing RFID transmission distance method;

Fig. 4 is a schematic structural diagram of the system of the present invention;

Fig. 5 is a schematic diagram of an embodiment of a layered RFID system for scanning labels inside a box according to the present invention.

Detailed ways

Hereinafter, the present invention will be described in detail in conjunction with the accompanying drawings.

Adding an additional RFID reader to an existing RFID system, the current RFID reader with AC or DC power is defined as a master reader (MR), and the newly added reader is defined as a slave reader (SR).

As shown in Figure 1, it is a structural schematic diagram of the slave reader of the present invention, and the structure of the slave reader is: add the radio frequency part of the transponder to the existing reader, and the slave reader of the present invention includes the radio frequency of the transponder unit and the master reader radio frequency unit, the transponder radio frequency unit and the master reader radio frequency unit are all connected to the control unit of the slave reader, and the slave reader transponder radio frequency unit and the reader radio frequency unit Connected to one or more antennas, one antenna can be used to receive and transmit RF signals (receiving and transmitting signals are time-shared), or 2 antennas can be used, one antenna is connected to the transponder RF unit of the RF unit , used to receive and transmit signals with the main reader; an antenna connected to the reader radio frequency unit of the radio frequency unit, used to receive and transmit signals with commodity labels. After the reader radio frequency unit of the slave reader is started, it communicates with the transponder of the commodity label through the antenna to obtain the information of the commodity label and store it in the memory of the slave reader. The memory is a readable and writable memory. The control unit of the slave reader transmits to the master reader through the radio frequency unit of the transponder and the antenna on the slave reader. The master reader collects information about the item tags from the slave readers and establishes an indirect connection between the transponder and the master reader. A slave reader is an active reader, which may be powered by an embedded battery or a vehicle or the like. When interacting with the master reader, the slave reader's transponder radio frequency unit is treated as a virtual RFID tag (active or passive), and the master reader operates as the slave reader's RFID reader. At this time, The embedded battery of the slave reader (or energy obtained by the electromagnetic wave of the master reader) supplies power to the chip of the radio frequency unit of its transponder, and when the tag is accessed, the embedded battery is used to supply power to the reader radio frequency unit and The control unit etc. is partially powered and the slave reader scans the real tag (both active and passive) as in the prior art.

Fig. 2 is a schematic diagram of the time sequence of the method of the present invention. Phase 1, the master reader emits an electromagnetic wave signal, and the radio frequency unit of the transponder of the slave reader collects the electromagnetic wave energy through the antenna for use by its own circuit (in the same way as the passive tag), or the transmitter of the slave reader The transponder radio frequency unit is activated by electromagnetic waves emitted by the master reader and powered by the slave reader's power supply. At the same time, the master reader transmits a command message to the activated slave readers. Phase 2, the slave reader supplies power to components such as the reader's radio frequency unit and control unit through its own power supply according to the command information of the master reader, just like the reader in the prior art, transmits to the transponder such as an electronic tag An electromagnetic wave signal and a card reading command information. In stage 3, the passive transponder on the commodity label receives the electromagnetic wave signal sent by the above-mentioned slave reader, and returns information such as the unique identifier (ID) stored in the tag transponder to the slave reader. Stage 4, after the scanning is completed, the data of one or more commodity tags are collected in the memory of the slave reader, and the slave reader forwards the data to the master reader one by one (the frame structure does not change), this forwarding process It is the same way that the transponder transmits data to and from its reader in the prior art. In this hierarchical structure RFID system, the slave reader acts as the reader of the real tag and the tag of the master reader.

Both the master reader and the slave reader perform data conversion, as shown in FIG. 3 , which is a schematic diagram of data frame conversion in the present invention. Data such as the unique identifier stored in the transponder of an electronic tag is compressed into one frame and transmitted to the slave reader through the air interface. Both the frame structure and the air interface conform to a certain RFID standard, such as the standard of the RFID international standardization body (EPCglobal Class 1 Gen 2). When the slave reader correctly receives the frames from the plurality of commodity label transponders, it retrieves the unique identifier and other information and stores it in the readable and writable memory of the slave reader. At this time, the data frames of the tags can be sent to the master reader one by one, and the air interface between the slave reader and the master reader can be a standard interface; or after receiving all the data frames, the control unit of the slave reader can compress These data frames form the payload in a frame (the data information of multiple tags in the frame has interval marks), and the slave reader transmits the frame to the master reader through its transponder radio frequency unit and antenna, when the master reader After receiving the frame of the slave reader, the payload of the frame is decompressed, and the unique identifiers of multiple commodity labels are retrieved. The interface between the master reader and the user application system is also the interface in the existing system. In this way, the efficiency of synthesizing multiple unique identifiers into one frame for transmission is greatly improved compared with the efficiency of transmitting data frames one by one in the prior art.

Fig. 4 is a schematic diagram of the system structure of the present invention. The combination of the master reader and the slave reader defines a virtual reader (VR), which is transparent to the client application system and the transponder. The air interface between the slave reader and the transponder of the article tag complies with the ISO standard or the EPCglobal standard or uses the air interface between the transponder and the reader of an existing RFID system. Therefore, there will be no difference in communication between existing transponders and the virtual reader of the invention. The communication interface between the main reader and the user application system is also in accordance with the existing RFID system. Based on the above description, existing client application systems and transponders can be applied in the layered RFID system of the present invention without change. For the user, if the common RFID system has been constructed, the layered RFID system of the present invention does not need to replace any existing equipment. This can be achieved by adding one or more slave readers of the present invention. Just as the reader in the prior art can read multiple tags at the same time, a master reader can read multiple slave readers, or as shown in Figure 4, the master reader and the slave reader receiver The distance L between transponders can be significantly increased by adding a plurality of slave readers according to the invention in series. The transponder radio frequency unit of the layer 1 slave reader is connected to the master reader through the antenna, and the reader radio frequency unit of the layer 1 slave reader is connected to the transponder radio frequency unit of the downstream layer i slave reader through the antenna, layer i The reader radio frequency unit of the i slave reader is connected to the transponder radio frequency unit of the downstream layer n slave reader through the antenna, and the reader radio frequency unit of the layer n slave reader is connected to the transponder of the commodity label through the antenna, i is a positive integer from 2 to n. The upstream reader of the slave reader refers to the reader communicating with its transponder radio frequency unit, which can be a common reader or the slave reader of the present invention; the downstream of the slave reader A reader refers to a tag or slave reader of the present invention that communicates with its reader radio frequency unit.

Typical RFID transponders harvest energy and transmit data via radio waves. Unfortunately, radio waves cannot penetrate and bounce off metal, making it impossible to read the transponder's data. In container conveying systems, it is often the case that RFID readers cannot read tags contained in metal containers.

FIG. 5 is a schematic diagram of an embodiment of a layered RFID system for scanning labels inside a box according to the present invention. Install a slave reader on the container or container, and extend the two antennas of the slave reader on the box, one of which is the antenna of the radio frequency unit of the transponder of the slave reader, facing the main reader The other is the antenna of the reader radio frequency unit of the slave reader, facing the transponders inside the box. The master reader transmits an electromagnetic wave signal to the antenna outside the box as an energy source for activating the radio frequency unit of the transponder of the slave reader on the box. The reader radio frequency unit of the slave reader emits an electromagnetic wave signal through the antenna inside the container to scan the object tags in the container. The slave reader's transponder radio frequency unit then forwards the collected data to the master reader via an antenna on the outside of the container, just as the transponder sends a unique identifier to the reader. Of course, in this application, the signal transmission distance between the main reader and the product label can also be increased by connecting the slave reader in series.

In this RFID application scenario, the working range of the layered RFID system can be greatly expanded, and further, the tags inside the metal box can be directly acquired at any time, without the need for the current traditional RFID technology open box to check.

The beneficial effect of the present invention is that, by using the slave reader as a relay device, the effective distance between the master reader and the tag is increased. There is little change to the RFID system in the prior art, only a slave reader is added, so the cost of the system is very low. By compressing the data of multiple tags, the efficiency of the reader to read multiple tags at the same time can be improved. The system is highly scalable and can be used for a variety of purposes, for example, it can be used to read RFID tags inside metal cargo boxes.

The above specific embodiments are only used to illustrate the present invention, but not to limit the present invention.

Claims (11)

1. An RFID reader comprising, a readable and writable memory, connected to the control unit, for storing information of at least one transponder; a reader radio frequency unit, connected to said control unit, for modulating and demodulating radio frequency signals with at least one of its downstream transponders; It is characterized in that it also includes: a transponder radio frequency unit, connected to said control unit, for modulating and demodulating radio frequency signals between its upstream reader; at least one antenna, connected to said transponder radio frequency unit and reader radio frequency unit, for transmitting and receiving signals between its upstream reader or downstream transponder; Said control unit controls said reader radio frequency unit to collect information of at least one transponder downstream thereof, stores said information in said readable and writable memory, and controls said transponder radio frequency unit to read upstream The device transmits the information. 2. A RFID reader according to claim 1, characterized in that there are two antennas, one is connected to the radio frequency unit of the transponder, and the other is connected to the radio frequency unit of the reader. 3. A layered RFID system comprising, a master reader, at least one remote transponder; characterized in that it comprises: at least one slave reader, coupled between said master reader and said at least one remote transponder, the reader radio frequency unit of the slave reader collects said at least one remote transponder response via at least one antenna information from the transponder radio frequency unit of the reader or the downstream slave reader, and the transponder radio frequency unit of the slave reader transmits the information to the reader of the master reader or the upstream slave reader via the antenna radio frequency unit. 4. A kind of hierarchical RFID system according to claim 3, characterized in that at least two said slave readers are hierarchically connected in series between said master reader and said at least one remote transponder In between, the transponder radio frequency unit of the layer 1 slave reader is connected to the master reader through the antenna, and the reader radio frequency unit of the layer 1 slave reader is connected to the downstream layer i slave reader through the antenna The transponder radio frequency unit, the reader radio frequency unit of the layer i slave reader is coupled via said antenna to the transponder radio frequency unit of the layer n slave reader downstream thereof, the reader radio frequency unit of the layer n slave reader The antenna is connected to the remote transponder, and i is a positive integer from 2 to n. 5. A kind of layered RFID system according to claim 3 or 4, characterized in that, there are 2 antennas, one is connected to the transponder radio frequency unit of the slave reader, and faces towards the master a reader radio frequency unit of a reader or its upstream slave reader; a reader radio frequency unit connected to said slave reader and directed towards the transponder of said remote transponder or its downstream slave reader unit. 6. A method for RFID system layered transmission, characterized in that, Step 1, the reader radio frequency unit of the slave reader communicates with at least one remote transponder or the transponder radio frequency unit of its downstream slave reader through at least one antenna under the control of the slave reader control unit, and obtain relevant information; Step 2, the transponder radio frequency unit of the slave reader communicates with the reader radio frequency unit of the master reader or its upstream slave reader through the antenna, and sends the information to the master reader or its upstream reader Transmitted by the reader RF unit of the upstream slave reader. 7. The method for layered transmission of a kind of RFID system according to claim 6, is characterized in that, before said step 1, also comprises a starting step, the transponder radio frequency unit of described slave reader passes through described The antenna receives the signal of the reader radio frequency unit of the master reader or its upstream slave reader, and transmits the signal to the control part of the slave reader to activate the reader radio frequency unit of the slave reader to perform the steps 1. 8. The method for layered transmission of a kind of RFID system according to claim 6, characterized in that, in said step 2, said slave reader collects said at least one remote transponder or The information of the transponder RF unit of its downstream slave reader is compressed into a payload in a frame and transmitted to the master reader or the reader RF unit of its upstream slave reader. 9. the method for a kind of RFID system layered transmission according to claim 6, is characterized in that, the transponder radio frequency unit of described subordinate reader is active or passive, and described reader radio frequency unit is active or passive. source. 10. The method for layered transmission of a kind of RFID system according to claim 6 or 7 or 8, characterized in that there are two antennas, one of which is connected to the radio frequency unit of the transponder and faces towards the a reader radio frequency unit of a master reader or its upstream slave readers; a transponder radio frequency unit connected to said reader radio unit and directed towards said remote transponder or its downstream slave readers. 11. A layered RFID system for scanning transponders located behind a shield, comprising, a master reader, at least one remote transponder, the shield, the at least one remote transponder in On one side of the shield, the main reader is on the other side of the shield, characterized in that, Also included is a slave reader mounted on the shield with two antennas, antenna 1 on the master reader side of the shield and antenna 2 on the remote transponder side of the shield The transponder radio frequency unit of the slave reader transmits signals with the reader radio frequency unit of the master reader or its upstream slave reader through the antenna 1, and the reader radio frequency unit of the slave reader passes through The antenna 2 transmits signals with the transponder radio frequency unit of the at least one remote transponder or its downstream slave reader; the reader radio frequency unit of the slave reader collects the Information of at least one remote transponder or the transponder radio frequency unit of its downstream slave reader is transmitted via the transponder radio frequency unit of said slave reader and said antenna 1 to said master reader or Reader RF unit of its upstream slave reader.

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