ES2391052T3 - Spatially selective UHF near-field microcintas coupler device and RFID system using the device - Google Patents

Abstract

A system comprising an RFID transceiver (42), the system being adapted to communicate exclusively with a single transponder located in a predetermined operating region of the transponder, said system comprising: a near-field coupler (30) having a property of spatially selective near field, which extends into the operating region of the transponder; in which the near field coupler having a plurality of electrically interconnected lines (50) in parallel, and a separate ground plane (9), such that the system is configured to establish, at predetermined transceiver power levels, a mutual coupling that is selective exclusively for a single transponder located in said transponder operating region, and which is characterized in that the near field coupler terminates by a terminal resistor selected to not match a characteristic impedance Static of the plurality of lines.

Description

Spatially selective UHF near-field microcintas coupler device and RFID system using the device

Background of the invention

1. Field of the invention

The present invention relates to RFID systems, operable with a variety of electro-magnetically coupled transponders of different dimensions, working in close proximity to an RF transceiver antenna that is spatially selective, for an individual transponder that is located in a default transponder operating region to exclude other adjacent transponders, and its application to printers - encoders or other systems using such UHF RFID systems.

2. Description of the related technique

US-A-2002/0167397 describes an RFID tag verifier, which includes an RF interrogator that transmits first and second interrogation signals, each having a first operating characteristic that differ from each other in a known quantity The RF interrogator receives first and second return signals corresponding to the respective interrogation signals. A processor determines an RFID tag response as defined by a second operating characteristic of the first and second return signals. The verifier can determine the signal strength of the return signal to vary the intensities of the interrogation signal. Typically, a flat response is desired. Additionally, or alternatively, the verifier may determine the response in terms of signal strength of the response signals for interrogation signals having different frequencies. In some applications, frequency selectivity may be desirable. Additionally, or alternatively, the verifier may determine the response in terms of the frequency of the interrogation signals that have varying intensities. A machine-readable symbol verifier may be coupled to, or be part of the RFID verifier. A printer can be attached to, or be part of the RFID tag verifier.

UHF radio frequency identification (RFID) technology allows wireless acquisition and / or transmission of data to active (battery powered) or passive transponders, using a backscatter technique. To communicate with the transponder, that is, "read", and / or "write" commands and / or data thereon, the transponder is exposed to an RF electromagnetic field by the transceiver, which is coupled with, and energizes the transponder (if passive) by means of electromagnetic induction and transfers commands and data using a predefined RF "signaling interface" protocol.

When multiple passive transponders are within the range of the same electromagnetic field of the RF transceiver, each will be energized and attempt to communicate with the transceiver, potentially causing errors in the "reading" and "writing" in a specific transponder in the reader field . There are anti-collision management techniques to allow almost simultaneous reading and writing in numerous transponders closely grouped in a common RF electromagnetic field. However, anti-collision management increases the complexity of the system, the cost and the delay in response. In addition, anti-collision management is "blind" since it cannot recognize where a specific transponder that is being processed in the RF electromagnetic field is physically located, for example, that the transponder is located close to the printhead of a printer-encoder.

One way to avoid errors during transponder reading and writing without using anti-collision management is to electrically isolate a specific transponder of interest from nearby transponders. Previously, the isolation of the transponders has used RF-protected housings and anechoic boxes or cameras through which the transponders pass individually to be subjected to a personalized exposure in the interrogation RF field. This requires that individual transponders have complex protections or significant spatial separation.

Printers - RFID encoders have been developed that can print on demand on labels, tickets, plates, cards or other media to which a transponder is attached or integrated. These printers - encoders have a transceiver so that they can communicate on demand with the transponder in the individual media, to read and / or store data in the attached transponder. For the reasons stated, it is highly desirable in many applications to present the media in rolls or other format in which the transponders are placed with a narrow spacing. However, the narrow separation of the transponders exacerbates the task of communicating in series with each individual transponder without communicating simultaneously with the neighboring transponders in the media. This selective communication exclusively with an individual transponder is further aggravated in printers - encoders designed to print on media in or near the same space in which the transponder is placed when it is being interrogated.

When transponders attached to a carrier substrate are supplied, for example on labels, tickets, plates, or other attached RFID media supplied in rolls, Z-folded batteries or other format, an additional length of the carrier substrate is necessary to allow a transponder on the carrier substrate it leaves the isolated field area before it enters the next in-line transponder. The extra carrier substrate increases the costs of the materials and the volume required of the bulk supply of the transponder means for a given number of transponders. Increasing the separation between transponders can also slow down the overall performance of the printer - encoder.

When transponders of different sizes and form factors are processed, RF protection and / or anechoic chamber configuration will also require reconfiguration, which adds cost, complexity and overall productivity reduction. In some printers - encoders it is desired to print on a medium mounted on the transponder in the same region of operation of the transponder in which it is being read from, or written on the transponder. This can be very difficult to achieve if the transponder must also be isolated in a protected housing or chamber.

UHF transponders can work, for example, in the 902 to 928 MHz band in the United States and in other designated ISM bands in different parts of the world. For example, in Fig. 1, a prior art coupler 3 of conventional "Direct Wave" micro wavelengths of conventional half-wavelength, consisting, for example, of a rectangular conductive tape 5 on a printed circuit board 7 having a separate ground plane layer 9 configured for these frequencies. One end of the conductive tape 5 is connected to a transceiver 42 and the other end is connected through the terminal resistor 8 to the ground plane 9. The conductive tape 5, as shown in the figure, has a significant width due to RF design requirements imposed by the need to create acceptable frequency response characteristics. This type of prior art coupler 3 has been used with UHF transponders that are relatively large compared to the extension of the prior art coupler 3.

As shown by Figures 2a and 2b, the newly developed transponders 1, designed to operate with UHF frequencies, have a reduced dimension in such a significant way, in the present specification, for example, a few millimeters wide, which will be activated with the next step of the larger prior art coupler 3 by the leakage of electromagnetic energy 10 concentrated on any side edge of the conductive band 5 of the prior art coupler 3. In Fig. 2A, the two leakage regions "A" and "B" defined by the leakage of electromagnetic energy 10 are small and relatively separate, which increases the overhead of the logic system and the transport transport positioning accuracy requirements of media. If the transponders 1 were placed together, the multiple transponders 1 could be activated by the coupling 3 of the prior art of "Direct Wave" micro-tapes of physically extensible half wavelength.

Therefore, the minimum required separation of these transponders 1 to isolate them, and therefore the minimum size of the means 11 (assuming that there is one integrated in each label or medium 11 on the carrier substrate 13) must be large in relation to The size of the micro-strip coupler 3. This creates problems for media providers because of the limited space available in the means 11 for the placement of transponder 1 and significantly increases the necessary accuracy of placing transponder 1 inside and / or under the printable means 11 and along the carrier lining or substrate 13. This also reduces the cost-of-use advantages of the transponders or narrow dimensions 1 within the means 11, since the means 11 must be much larger than the transponder 1 to achieve adequate RF isolation.

Competition in the market for this type of "integrated" printer-encoder systems, as well as other RFID interrogation systems has focused attention on the ability to interrogate with high spatial selectivity to any transponder from a wide range of available transponders that They have different characteristics of size, shape and coupling as well as minimizing the total system, media size, and transponder costs.

Therefore, it is an object of the invention to provide a system as shown in claims 1 to 4 and a method as shown in claims 5 to 8, which overcome the deficiencies in the prior art.

Brief description of the various views of the drawings

The accompanying drawings, which are incorporated and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above and the detailed description of the embodiments given to Then they serve to explain the principles of the invention.

Figure 1 is a top view of a prior art micro-wave direct wave coupler.

Figure 2a is a simplified side view cut out of a transponder-coupler structure using a prior art direct wave coupler as shown in Figure 1, which schematically illustrates positions where coupling with a transponder can occur. of narrow dimensions supplied in line with other transponders on a carrier substrate.

Figure 2b is a partial schematic top view cut out of the prior art direct wave coupler and the carrier substrate with the integrated transponders of Figure 2a.

Figure 3 is a schematic side view of a media printer according to an embodiment of the invention, which has an improved RFID interrogation system.

Figure 4a is a top view of a coupler according to an embodiment of the invention.

Figure 4b is a top view of a coupler according to another embodiment of the invention.

Figure 5a is a simplified side view cut out of a transponder-coupler structure using a coupler according to the invention, schematically illustrating the separate areas in which the coupling can occur with a narrow-sized transponder supplied in line with other transponders on a carrier substrate.

Figure 5b is a schematic partially cut-away top view of the coupler according to the invention and of the carrier substrate with the integrated transponders of Figure 5a.

Figures 6a and 6b are top views of carrier substrates illustrating different positions of the RFID transponders in accordance with other embodiments of the present invention.

Figure 7 is a graph illustrating the power levels with which the transceiver can communicate with an exemplary transponder at a particular distance from the transponder.

Figure 8 is a graph illustrating a look-up table according to an embodiment of the present invention, to provide the characteristic values of the transceiver's power levels to communicate with particular types of transponders.

Figure 9 is a three-dimensional graph illustrating the success rate of reading of a particular type of transponder with different power levels and positions in relation to the transceiver.

Figure 10 is a two-dimensional diagram corresponding to Figure 9.

Figure 11 is a three-dimensional graph illustrating the success rate of reading of a particular type of transponder with different frequencies and positions in relation to the transceiver.

Figure 12 is a two-dimensional diagram corresponding to Figure 11.

Detailed description of the invention

The present inventions will now be described in more detail herein and below, with reference to the accompanying drawings, in which some, but not all, embodiments of the invention are shown. Indeed, these inventions can be made in many different ways and should not be construed as limited to the embodiments set forth herein; on the contrary, these embodiments are provided so that this disclosure satisfies the applicable legal requirements. The same numbers refer to the same elements in everything that follows.

The present invention relates to an apparatus and method that allows an RFID transceiver (sometimes referred to herein as "interrogator") to selectively and exclusively communicate with a single UHF transponder 1 when one or more other similar transponders They are in close proximity, without the need for physical isolation or uncomfortable sheltered accommodation or cameras.

The invention is useful for reading and / or for loading data from UHF transponders, for example on an assembly line, in distribution centers or warehouses where RFID tagging is required on demand, and in a variety of other apps. In many applications, a transponder or a number of transponders are mounted or integrated on or on a label, ticket, plate, card or other means that are transported on a liner or carrier. It is often desirable to be able to print on the media before, after or during communication with a transponder. Although this invention is disclosed herein in a specific embodiment for use with a direct thermal or thermal transfer printer, it can also be used with any type of spatially selective RFID interrogation device or other types of printers using other printing technologies, including inkjet, matrix, and electro photographic procedures.

In some applications, a printing station may be located at a certain distance from the RFID transceiver; in others it may be necessary to carry out the printing function in the same objective space occupied by the transponder when it is being interrogated.

Figure 3 illustrates, by way of example only, an implementation of the invention in a thermal transfer media printer 16 in which both printing and communication with the transponder are performed,

but in different places in the media printer 16. The media printer 16 includes a subset of the printhead comprising a conventional thermal printhead 18 and the platen roller 19, such as in a direct thermal printer for printing on thermally sensitive media. A band 24 of means 11, such as labels, tickets, plates or cards, is directed along a feed path 26 under the printhead 18, where printing on demand of text, bar codes is carried out. and / or graphics, under the control of a computer or a microprocessor (not shown). After being printed, the means 11 follow an exit path 34 of means and can be detached from the underlying carrier substrate 13 by means of a detachment bar 32. The carrier liner or substrate 13 for the media is guided out of the printer. means 16 by a roller 36, leaving the printer along a carrier exit path 38.

When a thermal printer is configured for use as a thermal transfer printer, a ribbon supply roll 28 delivers a thermal transfer ribbon (not shown for clarity) between the printhead 14 and the media arranged in the band 24 After use, the spent tape is collected in a pickup reel 22.

In accordance with one aspect of the present invention, the media printer 16 includes a transceiver 42 for the generation of RF communication signals that are fed to a frequency-coupled and spatially-located near-field coupler 30 near the path of media feed 26. As will be explained and illustrated in detail herein, and then the system (including transceiver 42 and near field coupler 30) forms a near field pattern at the position of an operating region C of the transponder (see Figure 5A). The system is configured to establish, at predetermined levels of transceiver power, a mutual coupling that activates and communicates exclusively with a single transponder 1 located in the transponder operating region C

As the labels or other means 11 with integrated transponders move along the media feed path 26 through the operating region "C" of the transponder, the data can be read from or written to each transponder 1. The clues of information can then be printed on an external surface of the means 11 when the means pass between the platen roller 19 and the print head 18 by the selective excitation of the heating elements in the print head 18, as is well known in the technique When the media printer 16 is configured as a direct thermal printer, the heating elements form image points by the change of thermochromic color in the heat sensitive media; When the media printer 16 is configured as a thermal transfer printer, then the ink dots are formed by the ink melting of the thermal transfer ribbon (not shown for clarity) delivered between printhead 18 and the media in the band 24 from the loop supply roller

28. Dot patterns printed in this manner form the desired information signs in media 11, such as text, bar codes, or graphics.

Media transport is well known in the art. Therefore, the media transport portion 25 of the printer that drives the transponder media along the media feed path 26 is not described in detail.

The near field coupler 30 according to the invention and its mode of operation will be described below with reference to Figures 4a-5b. An embodiment of the near field coupler 30 is configured for use, for example, with UHF RFID transponders. The RFID transponders 1 can be supplied in bulk on a conveyor substrate 13 connected or integrated in the means of labels, tickets, cards or plates 11.

The near field coupler 30 comprises a set of lines 50, as shown for example in Figures 4a and 4b. The near field coupler 30 can be configured as a mismatched line segment 50 on a dielectric substrate, for example a printed circuit board 7, having a ground plane 9 formed on a separate insulated layer, for example, the back of the printed circuit board 7. One end of the line set 50 is connected to the transceiver 42; the other end is connected to the ground plane 9 by means of the terminal resistor 8.

Instead of functioning as a standing wave radiating antenna, or magnetic field generating coil, the near field coupler 30 according to the invention functions as a mismatched transmission line of half wavelength, for example, with an impedance 15 ohm characteristic that ends with a terminal resistance 8 of R = 50 ohm. The signals generated by the transceiver 42 that pass along the transmission line generate a near-field effect emanating from the edges of the transmission line that are coupled with a transponder 1 that passes through the operating region of the transponder Another description of the near-field effect is "fleeting," as explained in the document "Fuzzy Fields in Microcintas."

L. O. McMillian et al. Progress in Electromagnetics Research, PIER 17, 323-337, 1997 and which is incorporated herein by reference in its entirety. Because the near-field effect is extremely local to the transmission line and degrades at an exponential rate as the distance from the transmission line increases, the resulting operating region of the transponder of a single transmission line is very narrow. According to the invention, the above rectangular conductive band is therefore replaced by a

set formed by a plurality of lines 50 commonly fed and terminated, that is, electrically parallel, as shown for example in Figures 4a and 4b. The plurality of lines 50, therefore, creates a set of fleeting edges, as shown in Figure 5a, each fleeting edge creating an electro power leakage.

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 magnetic 10 at various points within the operating region C of the transponder. The resulting set of lines has a total width similar to the previous solid microcouple coupler 3 and can be tuned in a similar way, by configuring the length, separation and dielectric properties between the lines 50 and the ground plane 9 as well as the number of lines 50 and / or individual line widths, shapes and inter-separation, to adjust the total set as a single integrated electrical structure to have the desired frequency response characteristics and generate a combined near-field effect corresponding to a region of the desired transponder operation.

As shown by Figures 5a and 5b, the operating region C of the total transponder that is produced by a near-field coupler 30 according to the invention is substantially uniform. Preferably, the distance between the coupler 30 and the band 24 is selected for the critical coupling. That is, the distance is selected to be the one that supplies the maximum power just before being so close to the band 24 that the passing transponder (s) 1 make the effective impedance of the coupler 30 vary unacceptably.

In some applications, for example, the modification of an existing printer configuration to add an RFID read / write capability, the coupler 30 may be placed near the band 24 as a result of the available space and other design considerations, such as the positioning of the operating region C of the transponder close to the printhead 18. When the coupler 30 and the band 24 are in close proximity to each other, a mismatch of impedance may occur, since the electrical interaction with the or the transponders 1 passing varies the effective impedance of the coupler 30. The lack of impedance matching will decrease the coupling range for a given output power and significant impedance variations can cause narrow null gaps in the operating region C, for example as illustrated by d, e, f and g in figure 5a, between the individual fields emit gone for each line 50.

The simplified logic added to the media transport system can be used to move the means 11 forward a small increase, for example 1-2 millimeters, if a transponder 1 in the operating region C of the transponder falls over a null hole and They lose communications with the transponder.

The null gaps and the ability to control their presence by manipulating the position of the coupler 30 with respect to the band 24, are evidence of the extremely local field concentrations produced by the near field effect and the precision with which You can configure the operating region of the transponder to have a wide area with well-defined limits. These features make the near field coupler 30 useful for eliminating transponder placement requirements precisely for media suppliers, the complex position of the transponder and the tracking logic in media delivery systems, as well as any requirements. to protect or increase the transponder placement tolerance requirements. Furthermore, the region C of the increased transponder provided by the present invention allows users greater freedom to place the transponder (s) 1 integrated in the means 11 in the desired positions, for example to avoid the degradation of printing that can be occur when the printhead encounters an irregularity of the media surface due to the presence of an RFID transponder 1.

The line set 50 of the near field coupler 30 may be formed by a plurality of straight lines 50 as shown in Figure 4a. To further tune the near field produced by the line (s) 50, a zigzag or agitation can be applied to each line 50, as shown for example in Figure 4b, to further reduce the appearance and / or depth of the field strength gaps d, e, f, and g. For the purposes of this specification, "zig-zag" is defined as a characteristic of a line that has a characteristic of total length, but a plurality of internal address changes in the total length of the line. Changes of direction can be defined, for example, with sharpness or occur as smooth curves.

Alternatively, a simplified reading and / or writing system can be formed on a transponder 1 without printing capabilities by placing a near-field coupler 30 coupled to a transceiver 42 near transport means 25 that move sequential transponders 1 through of an operating region C of the transponder. This structure is also useful when the media 11 is unprinted, or is printed elsewhere.

The near field coupler 30 is not limited to a double plane structure. For example, the near field coupler 30 can be coplanar, that is, the ground plane and the set of lines 50 can be located, electrically isolated from each other, on the same plane of a printed circuit board, but on traces different. Also, the lines 50 need not be coplanar, but can form a 3-dimensional structure. For example, the lines 50 may be in multiple layers of a printed circuit board or formed as a wire frame of lines 50 without the use of printed circuit board technology.

Obviously, at some power level of the exaggerated transceiver, certain transponders 1 outside the transponder operating region C can be excited. However, by the present invention, with appropriate power levels in the range of normal transponder read and write power levels, the mutual coupling created will be highly selective for transponder 1 in the operating region C of the transponder by mapping. and then applying only the power levels required for a range of both types and positions of different transponders 1 within the transponder operating region C, energy consumption and potential RF interference generation can be minimized.

The spatially selective near-field property and the lack of any other protection requirements of the near-field coupler 30 according to the invention, allow the economic addition of a spatially compact, selective transponder communication module in devices such as printers - encoders

Because the near field coupler 30 can be configured to be selective exclusively for a single transponder located in the transponder operating region C, it is now possible by the present invention, the use of a band 24 of means having transponders which are tightly separated in the band 24, as shown for example in the figures of this specification. Before this invention it was extremely difficult to communicate with only one electro-magnetically coupled UHF transponder, which could have a large number of different physical configurations, in a tightly separated series of transponders without simultaneously activating adjacent transponders.

According to another embodiment of the present invention, the printer 16 can be configured to energize the transceiver 42 with different power levels to communicate with the transponders 1. For example, the transceiver 42 can be controlled by a controller 60, as shown in Fig. 3. In some cases, the controller 60 may be a printer driver that controls other functions of the printer 16, such as the operation of the printhead 18, the supply of the media band 24, 11, and the like. . The controller 60 can operate according to predetermined instructions, such as a software program that is stored in a memory 62.

The controller 60 may be configured to operate the transceiver 42 with a higher power while writing on each transponder 1 and while reading from each transponder 1. For example, in a typical operation of the printer 16, each transponder 1 is read first by transceiver 42 and then undergoes a subsequent write / read operation. In the first read operation, the transceiver 42 can retrieve data from the transponder 1, such as the type of transponder 1, a serial number that identifies the particular transponder 1, information on the means 11 to which the transponder is attached 1, or similar ones. In addition, the transceiver 42 can determine by the first read operation whether the transponder 1 is defective. In the subsequent read / write operation, transceiver 42 writes data to transponder 1 and then reads at least some of the data from transponder 1 to verify that transponder 1 is functioning properly, that is, the data was actually stored in the transponder 1 during the write operation. The controller 60 can operate the transceiver 42 with a first power level during each of the read operations, and with a second level, power during the write operation. The power levels of each of the read and write operations can be optimized to provide effective reading and writing on a particular transponder 1 without reading or writing on other transponders 1 on the carrier substrate 13.

Typically, for a transponder 1 in a particular proximity to the near field coupler 30, the transceiver 42 must provide greater power for writing on transponder 1 than for reading on transponder 1. That is, the power requirement for writing on transponder 1 is greater than the power requirement to read. Thus, in accordance with an embodiment of the present invention, the transceiver 42 can be energized with a higher level during the writing operations so that the transceiver 42 can write on the transponder 1 provided that the transponder 1 finds the Close enough for reading by transceiver 42 with the lowest reading power. In other words, transceiver 42 can be configured so that the region in which transceiver 42 can effectively write on transponder 1 is the same, or substantially the same, as the region in which transponder 1 can read with effectiveness on the transponder 1. By controlling the power of the transceiver 42 in this manner, the controller 60 can provide enough power to read, and write on a particular transponder 1, while avoiding reading and writing on other transponders 1 that are outside a designated position range.

A higher level of energy during the writing operation in general increases the probability that transceiver 42 writes on transponder 1, despite variations in the position and configuration of transponder 1. As shown in Figures 5a and 5b and explained above, the transponder 1 can have a relatively short dimension in the feed direction of the carrier substrate 13, so that the transponders 1 define between the same relatively long spaces and only one transponder 1 is affected by the leakage regions different from the narrow field coupler 30. However, in other embodiments of the present invention, it may be desirable to provide transponders 1 with different configurations and / or in different positions. For example, as shown in Figure 6a, each transponder 1 can be extended a greater distance in the feed direction along the feed path 26 of the printer 16, such that the space between the transponders 1 is reduced . In addition, as shown in Figure 6b, the placement of

The transponders 1 on the carrier substrate 13 may be non-uniform. That is, some of the transponders 1 may be closer to one of the transverse edges of the carrier substrate 13, and / or the successive transponders 1 along the carrier substrate 13 may define non-uniform distances between them. In some cases, such variations and / or lack of uniformity in the configuration and placement of the transponders 1 may increase the effective distance between the next field coupler 30 and the transponder 1 in which it is being read or written. When writing with a sufficiently high power, the transceiver 42 can still write on one of the particular transponders 1, even if the transponder 1 is further from the transceiver 42. However, it is generally desirable not to use excessive power in the operations of writing, for example, to avoid writing inadvertently on adjacent transponders 1 along the carrier substrate 13. In addition, transceiver 42 can read on transponder 1 in particular using a lower read power to prevent reading on other transponders.

The power level of transceiver 42 during read and write operations affects the likelihood that transceiver 42 will read from or write to transponder 1 successfully. Generally, a range of power levels can be used to read or write on each of the transponders 1. However, if the power level of the transceiver 42 during a read or write operation is too low, the transceiver 42 cannot communicate successfully with transponder 1, that is, the data cannot be read or written to transponder 1. Alternatively, if the power level of transceiver 42 is too high, transponder 1 will become inactive, and communication will fail .

The minimum and maximum power levels of transceiver 42 to communicate with transponder 1 are affected by a number of component characteristics and operating conditions. For example, different types of transponders 1 are characterized by different antennas, chips, and operating protocols. Therefore, each type of transponder 1 typically has different requirements, including the required power level of the signal from transceiver 42 during communication. In fact, even among transponders 1 of a particular type, slight variations in the structure of each transponder 1 can affect the sensitivity of each transponder 1 and, therefore, the power requirements for communication. In some cases, the power requirements of transponders 1 of the same type vary by 50% or more. In addition, the power required to communicate with transponder 1 is determined, in part, by the proximity of transponder 1 to transceiver 42 and / or to the near field coupler 30. That is, if transponder 1 is closer to the field coupler. next 30, the minimum power level for communication between them is typically lower than if the transponder 1 is farther from the next field coupler 30. If the transponders 1 are arranged unevenly on the carrier substrate 13 as illustrated in Figure 6b, or if the carrier substrate 13 does not advance evenly increased distances along the feed path 26, various power levels may be required for communication between transceiver 42 and transponders 1. In addition, transponders 1 They typically have different sensitivities at different operating frequencies. In this regard, it is noted that while the transceiver 42 operates at a nominal frequency, such as 915 MHz, the actual operating frequency of the transceiver 42 varies over a range of frequencies, such as between approximately 902 MHz and 928 MHz. Within this range, each transponder 1 can respond to signals of different power levels of transceiver 42.

Figure 7 illustrates the power requirements of the transceiver 42 to communicate with a particular type of transponder 1, the transponder 1 being positioned in a particular proximity to the transceiver 42. In particular, lines 64, 66 are representative of the minimum power levels and maximum, respectively, to read on transponder 1 in a frequency range. That is, if transceiver 42 operates below the power level indicated by line 64 or above the power level indicated by line 66 for a particular frequency, transceiver 42 will not read successfully from transponder 1. Similarly , lines 68, 70 are representative of the minimum and maximum power levels, respectively, for writing on transponder 1 in a frequency range. That is, if transceiver 42 operates below the power level indicated by line 68 or above the power level indicated by line 70 for a particular frequency, transceiver 42 will not write successfully on transponder 1.

In some cases, a single power level of transceiver 42 can be used to read and write on transponder 1. For example, as shown in Figure 7, the maximum power level of the read operation may be higher, in some or all frequencies, that the minimum power level for the write operation. In this way, the transceiver 42 can be energized with a power level such as PRW that is within the acceptable ranges of power levels, at least for some of the operation frequencies, both read and write.

Alternatively, transceiver 42 may be energized with one or more different levels during each of the read and write operations. The values can be determined accordingly to maximize the probabilistic opportunity to achieve a successful communication with the transponders 1. The characteristic values of the different power levels can be stored in the memory 62, so that the controller 60 can access the values during the different operations and thereby control the transceiver 42, for example, according to the different instructions of a software program to control the operation of the printer 16. During typical read and write operations, the transceiver 42 can be energized at the first, read and write power levels PR1, PW1, respectively, as indicated in Figure 7. If an operation

communication between transceiver 42 and transponder 1 is unsuccessful, transceiver 42 can repeat the failed attempt with one or more different operating power levels. Of course, since the frequency typically varies throughout the operation of the transceiver 42, subsequent attempts can also be made on different frequencies. In this regard, Figure 8 illustrates a look-up table that can be stored in memory 62 and that includes a number of read power levels PR1, PR2, PR3, and write power levels PW1, PW2, PW3. Memory 62 may include any number of power levels for each type of operation. If the first attempt to read a transponder 1 at the first reading power level PR1 fails, the controller 60 can then operate the transceiver 42 at the second power level PR2 during a second attempt to read the transponder 1, since then, at a third power level PR3 during a third attempt to read transponder 1. In some cases, controller 60 may attempt to perform the operation at each frequency more than once. Typically, controller 60 is configured to attempt each operation no more than a predetermined maximum number of times before rejecting transponder 1 as defective. Of course, if the operation is correct before the predetermined number of attempts is reached, the controller 60 may proceed with the following operation, such as writing on transponder 1 or communicating with a subsequent transponder 1. Also, as shown in Figure 8, memory 62 can store other power levels PR1 ', PR2', PR3 ', PW1', PW2 ', PW3', PR1 ", PR2", PR3 ", PW1", PW2 ", PW3" to perform read and write operations with other types of transponders 1 or transducers 1 in other configurations. In any case, the writing power level for a particular type of transponder 1 may be greater than the reading power level for the same transponder 1. For example, in one embodiment, the writing power may be up to about 3 times greater than the reading power. In this way, transducer 42 can be configured to write and read in areas that are approximately the same size.

Figures 9 and 10 illustrate read success rates of a particular type of transponder 1 with different power levels and positions relative to transceiver 42. A series of "power configurations" between 60 and 200 are indicated along a first axis of the graph, each power configuration corresponding to a particular power value for transceiver 42. The proximity of transponder 1 in relation to transceiver 42 is indicated by the "label position" measured in millimeters along the path of power 26 of the printer 16. The read success rate is indicated along the third axis, that is, a percentage of the total attempts to read the transponder 1. The graph in Figure 9 was empirically constructed by means of tests of transponders 1 of a particular type and different power configurations and positions. Similar data can also be determined theoretically or by other procedures. Figure 10 is a two-dimensional diagram corresponding to Figure 9. That is, the power configuration and position values are indicated on the two axes, and the success rate is only indicated by intensity / darkness. The intensity values in general correspond to the rates indicated along the third axis of Figure 9, that is, generally varying in dark / high intensity (low success or unsuccessful) to light / low intensity (100% success).

In certain positions, the transceiver 42 achieves high success substantially regardless of the power of the transceiver 42. For example, for position values between about 15 and 23 mm, the reading success rate is high, except with very low power settings. . Similarly, at position values between approximately 35 and 43 mm, transceiver 42 communicates with great success, except with low power settings. With the highest power settings, the ranges of positions associated with high success rates are slightly larger than the ranges of positions with the lowest power settings. In this way, in a wide range of power configurations between approximately 90 and 180, a high reading success rate is achieved in two significant position ranges. However, it is also shown that a high success rate is achieved with power levels greater than approximately 130, for a position of approximately 50 mm. Therefore, the power configuration can be limited to a range of power configurations between approximately 90 and 110 in order to restrict the range of read operation positions, that is, to avoid reading multiple transponders 1 along the carrier substrate 13.

Similarly, Figures 11 and 12 illustrate the read success rates of a certain type of transponder 1 with different frequency levels and positions relative to the transceiver 42. That is, Figure 11 is a three-dimensional graph illustrating the success rate of reading a particular type of transponder 1 with a particular power, over a range of frequencies and relative positions with the transceiver 42. Figure 12 corresponds to Figure 11, with the reading success rate indicated only by intensity / darkness. In positions between approximately 16 and 21 mm and between approximately 36 and 42 mm, the success rate of reading is high and substantially independent of the frequency. Therefore, a high reading success rate can be achieved by operating transponder 1 with a power setting of between approximately 90 and 110, with transponder 1 being in positions between approximately 16 and 21 mm. In addition, in this range of power configurations, the reading success rate of transponders 1 located in other positions, for example, positions greater than about 46 mm, is low. Therefore, transceiver 42 can effectively read on a transponder 1 positioned in a relatively narrow range of positions, so that communication with other transponders 1 outside the position range is avoided.

Although the above graphs illustrate the importance of power, position and frequency in the reading success rate, it is appreciated that a similar analysis can be carried out to determine the applicable power, position and frequency ranges for the success rate. of transceiver 42 for a particular type of transponder 1. In this way, a range of power levels can be determined along which transceiver 42 reaches

a high write success rate with a transponder 1 located in a specified range of positions. If the position ranges for the read and write operations are substantially the same, the transceiver 42 may read and write on a transponder 1 located in the position range while avoiding communication with transponders 1 outside that range. Therefore, even if the transponders 1 are located close to each other on the carrier substrate 13, the transceiver 42 can communicate with a particular transponder of the transponders 1.

In some cases, the controller 60 can be configured to operate the transceiver 42 with different power levels according to other operating parameters such as the type of transponder 1, the type of carrier substrate 13 or the media band 24 11, and similar ones. For example, the sensitivity of transponder 1 to communication signals from transceiver 42 can be affected by carrier substrate 13, band 24, or other materials in close proximity to transponder 1. However, by setting levels Transceiver 42 power according to these factors, transceiver 42 can consistently achieve high success rates of communication with a transponder 1 in a predetermined position along the feed path 26 while simultaneously preventing accidental communication with other transponders 1 over the carrier substrate 13. The controller 60 or another member of the printer can automatically detect the operating parameters, for example, by reading the data of the transponders 1, so that the controller 60 can automatically use the corresponding power levels of memory 62. Alternatively, an operator can in Enter the operating parameters, or the printer 16 can be configured to use a predetermined level or levels of power, regardless of the type of transponder 1 on the carrier substrate 13.

In accordance with an embodiment of the present invention, a method for communication with a transponder is provided. The method comprises a) positioning a transponder in an operating region of the transponder, an axis of the transponder being oriented along a predetermined direction, the smallest dimension of said transponder being in said predetermined direction significantly smaller than a dimension of the transponder. said region of operation of the transponder in said predetermined address; b) with an RF communication signal, forming a set of near-field concentrations in said transponder operating region, said near-field concentrations extending transversely to said predetermined address and separated along said predetermined address, and c) communicating with said transponder with said RF coding signal, d) the separation of said near-field concentrations in said predetermined direction being significantly less than said smaller dimension of said transponder in said predetermined address, so that said transponder overlaps with and is excited by a plurality of said near-field concentrations when it is in said transponder operating region. In one case, a plurality of transponders individually communicates through a sequential passage through the region of operation of the transponder through the transport of the means.

A method for communicating with a transponder provided by another embodiment of the present invention comprises positioning the transponder on a separate set of near-field concentrations of an RF communication signal, the separation of said near-field concentrations is such in in relation to the dimensions of said transponder that said transponder overlaps and is excited by a plurality of said near-field concentrations. For example, the separate set may be a parallel set of leaking edges that have near field concentrations.

In another embodiment, the present invention provides a method of adaptively communicating with a transponder. The method comprises placing the adjacent transponder with a pattern of near-field concentrations separated from an RF communication signal, the pattern having at least one unwanted low energy zone within which the transponder communication is not performed in a manner optimal; excite the transponder with near field concentrations; confirm valid communication; If the valid communication is not confirmed, move the transponder a distance, repeating the said excitation, confirmation, and movement actions until a valid transponder communication is confirmed.

The present invention also provides a method for communication with transponders that has a size range from the smallest to the largest. The method provides a) forming, with an RF communication signal, a set of spaced near-field concentrations of a transponder operating region, the spacing of said near-field concentrations being less than the length and length dimensions. smaller width of said smaller transponder, such that all transponders in said size range overlap and are excited by a plurality of said near field concentrations when they are located close to said transponder operating region, b) position said transponder target sector close to a transponder having a size in said transponder size range, and c) communicate with said transponder.

In accordance with yet another embodiment of the present invention, a method of communicating with a transponder is provided. The procedure includes: forming, with an RF communication signal, a pattern of near-field concentrations in a region of operation of the transponder larger than the transponder; locating a transponder in a first position in the said region of operation of the transponder; determine a first level of operationally effective signal power to communicate with said transpon

dedor when it is located in said first position; storing said first power level aso

the position and position of the transponder; position said transponder or a similar transponder in a second

position in said transponder operating region; determine a second level of signal power

5 Operationally effective to communicate with the aforementioned transponder when it is in said second

position; storing said second associated power level and the position of the transponder; and communicate ope

rationally with a series of transponders located in the aforementioned first and second positions in the aforementioned

Transponder operating region using the first and second store signal power levels

nothing associated respectively with the first and second positions of the transponders in said operating region 10 of the transponder. In one case, the procedure also includes the storage of one type.

of the transponder.

Claims (7)

1. A system comprising an RFID transceiver (42), the system being adapted to communicate exclusively with a single transponder located in a predetermined transponder operating region, said system comprising: 5 a near field coupler (30) having a spatially selective near field property, which extends into the operating region of the transponder; wherein the near field coupler having a plurality of electrically interconnected lines (50) in parallel, and a separate ground plane (9), such that the system is configured to set, at predetermined transceiver power levels , a mutual coupling that is selecti 10 or exclusively for a single transponder located in said transponder operating region, and characterized in that the near field coupler terminates with a selected terminal resistor so that it does not match an impedance characteristic of the plurality of lines. 2. The system defined by claim 1, wherein the coupler is positioned at a distance from the transponder that does not significantly change an impedance characteristic of the coupler.

3.

The system defined by claim 1 further comprising transport means for transporting a band of labels through said transponder operating region, at least some of the labels having an RFID transponder.

Four.

The system defined by claim 1, which also includes means of transport for advancing from

20 incrementally forms the transponder within the operating region of the transponder, if the transponder is located in a field strength gap of the operating region of the transponder. 5. A method for establishing communication between a transceiver and a single transponder located in a predetermined confined transponder operating region, comprising: generate a nearby field in a transponder operating region, which varies in response to 25 a radio frequency input signal, forming the near field with a coupler having a plurality of electrically connected lines in parallel, and a separate ground plane, terminating the near field coupler with a selected terminal resistor so that it does not match a characteristic impedance of the plurality of lines, and establish at mutual power levels of the transceiver, a mutual coupling that is selective only for a single transponder located in said transponder operating region. 6. The method defined by claim 5, further including the step of placing the coupler at a distance from the transponder that does not significantly change an impedance characteristic of the coupler. The method defined by claim 5, which includes transporting a band of tags through said transponder operating region, at least some of said tags having an RFID transponder, and wherein said method It includes printing on the mentioned labels. 8. The method defined by claim 5, which further includes the step of advancing incrementally Mind the transponder within the transponder's operating region, if the transponder is located in a field strength gap of the transponder's operating region.