CN100470596C - Multi-loop antenna for radio-frequency identification - Google Patents

Abstract

The invention provides a multi-loop antenna (30) that produces an electromagnetic field having a magnitude of at least an interrogation threshold of a tag for a substantial portion of an interrogation region located in a plane parallel to the antenna. The antenna may include a plurality of loops, including one or more powered loops (32, 34) and one or more parasitic loops. The parasitic loops receive power from mutual coupling with the powered loops causing current to flow within the parasitic loops, which contributes to the profile of the magnetic field. As a result, each parasitic loop may be tuned to provide control over the magnitude of the electromagnetic field. The powered loops and the parasitic loops may be varied over the interrogation period to reduce any area of the interrogation region where the magnitude of the field remains below the interrogation threshold throughout the interrogation period. The powered loops and the parasitic loops may reside on a single layer or may be arranged on multiple layers (Fig. 5, 6).

Description

The multi-loop antenna that is used for radio-frequency (RF) identification

Technical field

The present invention relates to use the radio-frequency recognition system that is used for document and file management, and more specifically relate to the radio-frequency antenna that is used for radio-frequency recognition system.

Background technology

Be widely used in each industrial circle on radio-frequency (RF) identification (RFID) technical spirit, comprise transportation, manufacturing, waste management, postal tracking, the coordination of shipping luggage and the management of the highway expenses of taxation.Typical R FID system comprises the RFID label, has the RFID reader of antenna, and computing equipment.The RFID reader comprise can energy or information give the transmitter of label, and receive from the sign of label and the receiver of out of Memory.Computing equipment is handled the information that is obtained by the RFID reader.Generally speaking, specify specific application from the information that label receives, but be provided for the identification of the article that label is fixed to usually, these article can be article, vehicle, animal or the individualities of making, perhaps other palpable object in fact arbitrarily.Can also provide other data to be used for object.This label can use during manufacture process, for example, indicates spraying color or other Useful Information of automobile chassis during manufacture.

Transmitter makes label can return the electromagnetic field of the RF signal of the information of carrying by antenna output RF signal with establishment.Existing label can be " active " label that comprises internal electric source, perhaps by " passive " label of field excitation.

Transmitter uses amplifier with the output signal driven antenna with modulation.In case excitation, label uses predefined protocol communication, allows the RFID reader to receive information from one or more labels.Computing equipment is by coming as information management system from RFID reader reception information, and carries out some actions, such as new database more or give the alarm.In addition, computing equipment programs data into mechanism in the label with acting on through transmitter.

Summary of the invention

Generally speaking, the present invention relates to produce the multi-loop antenna of the electromagnetic field that is used for radio-frequency (RF) identification.For example, antenna can be embedded in the rfid system " storage areas ".As described in detail later, storage areas can be equipped with multi-loop antenna generating an electromagnetic field, and have RFID inquiry ability with help to follow the tracks of and positioning system in document or file.The RFID label that the article that the RFID inquiry ability of storage areas can read and store in each storage area are associated.The example of storage areas comprises shelf unit, cabinet, vertical file separator, intelligent vehicle, desktop type reader or similar position.

The embodiment of multi-loop antenna can be used in a lot of RFID application, and such as storage areas, wherein label possibility quilt is perpendicular to antenna direction.For reliable communication is provided, need be perpendicular to the direction of any RFID label that is associated with article in the storage area and be arranged on the antenna or be parallel to the big as far as possible magnetic field of establishment of " interrogation " on the plane of antenna.This embodiment produces to have and satisfies or surpass essential part for interrogation, and needs the magnetic field to the amplitude of the minimum inquiry threshold value of energize tags on the direction perpendicular to antenna.

In one embodiment of the invention, antenna comprises a plurality of loops.The loop orientation with the essential part for the interrogation that is arranged in the plane that is parallel to antenna, is produced the amplitude of the inquiry threshold value that has label at least.Can optionally provide energy in the inquiry cycle, and remaining loop is a parasitic loops to one or more loops.The loop of this parasitic loops warp and other energy supply intercouple received energy, make electric current in parasitic loops, flow, thereby DISTRIBUTION OF MAGNETIC FIELD (profile) contributed.Driving loop and parasitic loops can change in the inquiry cycle, keeps below the arbitrary region of inquiry threshold value with the amplitude that reduces interrogation internal field in this inquiry cycle basically.During the inquiry cycle, for example, to first group of loop energy supply and startup RFID communication.Combination in any for loop during the inquiry cycle can repeat this process.

In another embodiment, antenna is included in common plane, for example, forms a plurality of concentric loops in the individual layer of printed circuit board (PCB).Printed circuit board (PCB) can be used in, and for example, is embedded in the pedestal of vertical file or in one of storage areas of shelf.Antenna can comprise the concentric loops of arbitrary number, such as 3,5,10,15,20 or a plurality of concentric loops.As an example, antenna can comprise a plurality of loops of wherein giving outer shroud and interior ring energy supply in the inquiry cycle, and remaining loop can be a parasitic loops.Specifically, replace energy supply can for during the inquiry cycle outer shroud and interior ring, make for being positioned on the antenna or being parallel to the essential part of the interrogation of antenna, the amplitude during the inquiry cycle satisfies or surpasses the inquiry threshold value of label.

In another embodiment, antenna is included in a plurality of loops of each layer formation of printed circuit board (PCB).The loop of two energy supplies can be positioned on the top layer, and the loop of two other energy supplies can be positioned on the bottom.In the layer that one or more parasitic loops can be between top layer and bottom.Use three layers to form the printed circuit board (PCB) that is used in one of storage area.This loop can be a decentraction, and can be overlapping on the direction perpendicular to printed circuit board (PCB).

In another embodiment, system comprises the article that storage area has the RFID tag that is associated with storage, and the multi-loop antenna of close storage area is to generate an electromagnetic field.This system further comprise with antenna coupling with optionally at least one energy supply of the loop of antenna and not to the RFID reader of residue loop energy supply to communicate by letter with RFID tag.

In a further embodiment, the present invention relates to comprise optionally at least one loop energy supply of multi-loop antenna and not to the energy supply of residue loop, during the inquiry cycle, producing electromagnetic field near storage area, and during the inquiry cycle method of one or more RFID tag acquired informations of the article from be fixed to storage area.

Though many aspects major part of the present invention is described with document or file or both, the present invention can be used to follow the tracks of other article that comprise books, video-tape, optical recording media or retail item, tray, container or other assets, as long as suitable, no matter and these article each whether specifically proposition as other application.

Accompanying drawing and below instructions in one or more embodiments of the detail of the present invention are proposed.Can more clearly understand other features, objects and advantages of the present invention by instructions, accompanying drawing and claim.

Description of drawings

Fig. 1 shows the block diagram of radio-frequency (RF) identification (RFID) system that is used for document and file management;

Fig. 2 shows the skeleton view that is used for about the directed example of the antenna of the RFID reader of the label that is associated with document or file;

Fig. 3 is the synoptic diagram of an example embodiment of multi-loop antenna;

Fig. 4 A shows by the curve map of selectivity to the amplitude of the example magnetic fields of the different loop energy supplies generations of the antenna of Fig. 3;

Fig. 4 B show selectivity to the inquiry cycle of loop energy supply in the curve map of amplitude in magnetic field of Fig. 4 A;

Fig. 4 C shows the 3-D view by the amplitude of the magnetic field realization of Fig. 4 A in the inquiry cycle;

Fig. 5 is the planimetric map of another exemplary multi-loop antenna;

Fig. 6 is the decomposition view of the example antenna of Fig. 5;

Fig. 7 is the planimetric map of another example multi-loop antenna;

Fig. 8 A shows the curve map by the amplitude of the example magnetic fields of the multi-loop antenna generation of Fig. 7;

Fig. 8 B is the 3-D view by the magnetic field of the antenna establishment of Fig. 7.

Embodiment

Fig. 1 shows the block diagram of radio-frequency (RF) identification (RFID) system 10 that is used for document and file management.Although people are just considering office is converted to the situation of the no paper environment that paper sheet document wherein substituted fully by the electronic version of those documents, many industrial circles continue to rely on very much paper sheet document.Example comprises legal office, government bodies and the equipment that is used to store commerce, crime and medical record.These files can be arranged in a lot " storage areas " 12, for example, and in open clip 12A, cabinet 12B, vertical file separator 12C, intelligent vehicle 12D, desktop type reader 12E or similar position, as shown in Figure 1.

By this way, can provide storage areas 12 in in-house a plurality of positions, with relative with single file room.For example, storage areas 12 can and ad-hoc location,, for example, therefore the account shelf is associated, and is called as or is thought of as " special use " shelf.As what describe below, storage areas 12 can be positioned at independent office or for example, near other zone in hospital or clinic, law company, accounting firm, middle man room or the bank, so that not only when file is positioned at the hub file room, follow the tracks of them, when being positioned at the position of distribution, they also follow the tracks of them.

Usually use term " storage areas " to be used for being equipped with RFID inquiry ability to help document or the document of file or the storage area of other article of tracking and positioning system 10 with expression.Specifically, the RFID of storage areas 12 inquiry ability can read the label that is associated with the article of storing in each storage area.In other words, the RFID label can be associated with interested article and be applied to this article.Even label can be embedded in the packing of article or article, make label imperceptible at least basically, it can help prevent discovery and be altered.Like this, can be with RFID label " source marking " article, such as in manufacture process, the RFID label inserted article or with the RFID tag application in article, such as for file, document, books etc.

Can make RFID label or label by a plurality of manufacturers, comprise the title " Tag-it " of the Texas Instruments of Dallas Texas.One type RFID label is to comprise RFID element and the full combination of elements label of abampere.The RFID label typically comprises the integrated circuit of the storer with the amount of determining, the part of this storer is used for the information of determining is write label, and its another part is used to store other information to label.This integrated circuit is operatively coupled to and receives the RF energy from the source and with the antenna of the mode backscattering RF energy known this area.These backscattered RF energy provide and can be received by the interrogator in file tracker 14 (being commonly referred to reader), with the signal of the information of the article that obtain to be associated about RFID label and this label.

Rfid system 10 is operated in the frequency range of electromagnetic spectrum, such as 13.56MHz, but and have+/-tolerance frequency of 7kHz changes, it is generally used for industry, science and medicine (ISM) equipment.But, can use other frequency to be used for RFID and use, and the invention is not restricted to this.

The RFID interrogator of storage areas 12 or reader pad are transmitted positional information to the centre data storage is provided, for example, file tracker 14 in one or more databases of relational database management system (rdbms), that be used for concentrated position information.File tracker 14 can be networked, and perhaps is coupled to one or more computing machines and makes and can visit data about those article at the individuality of a plurality of positions.

The collection of positional information and to concentrate for a lot of purposes all be useful.For example, the user can ask special article or article group, such as the position of file or one group of books.File tracker 14 can be from data storage the retrieving files positional information, and be arranged in the rearmost position of one of storage area to the user report article.Alternatively, system again poll or with other, the mode position of current location that regain article to confirm that article are indicated in database.

As another example, file tracker 14 can be notified the user, and when article are positioned at certain position and are ready for use.For example, can notification agent people file be ready for and have browsed and be positioned at recently on the his or her desk.Very natural, file tracker 14 can be applied to the legal document stored in court room or law court, and by the judicial functionary, such as uses such as judge, clerks.Similarly, if patient's file is positioned at the appointed area, can notify (may pass through mobile phone or pager, or pass through Email) hospital personnel this document (may be the personnel that file relates to) to be ready to and can to have read.

File is positioned at the fact that certain location pending further handles can be by file tracker 14 records, as the part of the position history of those article.Noticing to be arranged in determines on shelf or other memory location or the people who determines wishes that the file of determining of work is different from and comprises that wait is by the storage room at the big group of file (possibility) of any personnel's work of group or tissue.In other words, the definite shelf with definite file of the personnel that are used to determine is specific for that people, yet general file room is equipped with the All Files that is used for not all members of the group of any one people's appointment.

In addition, the cycling time of the information of collecting by rfid system 10 in (for example) tracing process, aspect the efficient of one or more human efficiencies of paper work and process, be useful.These information can also provide information whether to remain on the type of the position archives in the software systems.

Each storage areas 12 of system 10 can be equipped with and be used to inquire that file is to help determining which file is positioned at one or more antennas of each storage area.For example, one or more antennas are arranged in shelves of open 12A and are used for electromagnetic field with RFID label communication associated with the file with establishment.Similarly, antenna can be positioned at cabinet 12B, vertical file separator 12C, intelligent vehicle 12D, desktop type reader 12E etc.Positioning antenna such as in the top or the bottom of each shelf, in the back or the vertical support of shelf, scatters hereof in many ways.Antenna can be present in the shelf or implants shelf and buy as the unit with other form.

Each storage areas 12 can comprise that antenna control system is inquired with active antenna or poll RFID label.If carry out poll continuously, the controller in antenna control system can comprise the circuit that is used for sequentially passing through the multiplex signal of a plurality of antennas.This antenna control system can be so that antenna be inquired the part of storage areas 12 with predefined procedure.Antenna control system can comprise one or more nodes, just, and sub-controller, the child group of its control antenna.Determine by the user with number, position and the further feature of given node associated antennas.For example, quick if desired poll shelf can add more node to system.Other method is that the user disposes or customizes antenna control system and makes the node of configuration storage areas 12 or part with by user's named order poll.For example, if a part of storage areas 12 is not useable for certain time, do not need to inquire at that regional RFID label at those time durations so.

As described in detail, can design the one or more antennas that are used in each storage areas 12 are determined intensity at least with generation in " interrogation " on storage area magnetic field here.This is useful for one or more reasons, comprises the file efficient accuracy of the whole interrogation of improving given storage areas 12.The magnetic field of being created by antenna is used to the label energy supply that is associated to article in storage areas 12, and the amount of the energy of responding in each label and the magnetic field intensity by tag loop are directly proportional.Preferably, use antenna to have the amplitude that surpasses the threshold amplitude that is used to encourage the RFID label with generation in the inquiry cycle.In addition, in the entire portion basically of interrogation, this amplitude satisfies or surpasses the inquiry threshold value that is used to encourage label, such as 115dBuA/m.For example, by selecting the different drivings and the parasitic loops of antenna, the field of generation can have on whole interrogation, surpasses the threshold amplitude of threshold amplitude basically for 50%, 70%, 90%, 99% or more zone of interrogation.By this way, antenna 30 can be used for the more accurate label communication that detects and be associated with article in storage areas 12.Therefore, described here technology can be improved all or the possibility of all labels basically that is associated with the file or document that is arranged in storage area, and can successfully detect article.

Fig. 2 shows the skeleton view about the directed example of the antenna 20 of the RFID reader of the label 22 that is associated with the article that are arranged in one of storage areas 12.Use at a lot of RFID, in the storage areas 12 such as rfid system 10, perpendicular to the direction of label 22 (as dotted arrow 21 indications), and be useful at the big as far as possible electromagnetic field of interrogation 24 establishments that is arranged on the antenna 20 and be parallel to the plane of antenna 20.Specifically, the field should on main direction perpendicular to label 22, have the amplitude that the minimum that satisfies or surpass needs excitation label is inquired threshold value, so that reliable communication to be provided in the entire portion basically of interrogation 24 in whole interrogation.

A lot of RFID parallel to each other unlike the top of wherein RFID reader and label and that aim at use, and antenna 20 in storage areas 12 and label 22 need oriented perpendicular to each other.Specifically, for easy for installation and other reason, antenna 20 may be arranged in each pedestal or the shelf structure of storage areas 12, perhaps along each pedestal or the shelf structure of storage areas 12, and vertically stores document or article.For example, one or more antennas 20 can be arranged in the shelf of shelves of open 12A.Similarly, one or more antennas 20 can be arranged in the pedestal of vertical file separator 12C.But the file or document in these storage areas 12 typically is arranged vertically.As a result, the label 22 that is associated with one of article tends to perpendicular to antenna 22 orientations, and may be positioned at the distance z on the antenna 20 of reader.In addition, according to the position of the article that are associated, label 22 can be positioned at the optional position on the zone that is occupied by antenna 20.For example, label 22 can be positioned near arbitrary end of shelf 12A, or optional position therebetween.

Existing monocycle RFID antenna may not produce the electromagnetic field that satisfies or surpass minimum inquiry threshold value on whole plane 24 basically perpendicular to the direction of label 22.Specifically, monocycle RFID antenna can encircle directly over produce field with peak field's intensity, and in the middle of antenna, have remarkable decline.As a result, existing monocycle RIFD antenna more out of true maybe can not be worked, because they may not detect a lot of article in storage area.As described here, each storage areas 12 is used and can be created in one or more multi-loop antennas that whole storage areas satisfies or surpass the magnetic field of the inquiry threshold value that is used to encourage label.

Fig. 3 is the synoptic diagram of an example embodiment of multi-loop antenna 30.Specifically, antenna 30 can produce wherein and to be arranged on the antenna and the interrogation of parallel antenna, satisfies or surpass the electromagnetic field of minimum inquiry threshold value in the amplitude of entering the court perpendicular to the direction of label orientation.Specifically, antenna 30 comprises a plurality of concentric loops of plane formation each other, just, is arranged in one or more parallel planes.

Antenna 30 comprises one or more " energy supply " loops and one or more " parasitism " loop to reduce in the whole inquiry cycle, and the amplitude of interrogation midfield keeps below the arbitrary region of inquiry threshold value.In addition, optionally the loop of the arbitrary number of energy supply antenna 30 is parallel to and the interrogation on plane on antenna surpasses the field of minimum inquiry threshold value being arranged in to be formed on the inquiry cycle.During the inquiry cycle, can first group of loop of energy supply and startup RFID communication.This process combination in any for loop during the inquiry cycle can be repeated.

Each loop can comprise that discrete track, circuit or other are suitable for the conductive path that electric current flows.In addition, one or more loops can be made of single, continuous track or circuit.As an example, can form loop by the one or more tracks in printed circuit board (PCB) or in other rigidity or the flexible substrate.For example, the width of each loop is 100 to 150 microns.A plurality of antennas 30 can expand to whole storage area to guarantee electromagnetic field in location adjacent one another are in single storage areas 12.

Generally speaking, parasitic loops is by coming received energy to make electric current flow in parasitic loops with the mutual coupling that drives loop, and this electric current contributes to DISTRIBUTION OF MAGNETIC FIELD.As a result, can tuning each parasitic loops with the meticulous control of amplitude that electromagnetic field is provided.According to the principle of field stack, during the interrogation spacing, be based on the contribution of all loops in the final field of arbitrfary point generation by antenna 30.Therefore, can select to drive loop and parasitic loops with dimension along antenna 30, for example, the meticulous controlling magnetic field of the directions X of Fig. 3.In addition, during the inquiry cycle, can change the powered loops of antenna 30 and parasitic loops forming essential part, on direction, satisfy or surpass the field of the amplitude of inquiry threshold value perpendicular to the orientation of the label in the interrogation for interrogation.

In one embodiment, antenna 30 can comprise the loop of arbitrary number, such as three, five, ten, 15,20 or more concentric loops.Measuring outer shroud 32 at directions X is about 12 inches, and in 8 inches in Y direction.In addition, the loop that can arrange antenna 30 has about 0.4 inch interval between the center of each ring.

Can be to the outer shroud 32 and 34 energy supplies of interior ring of antenna 30, and ring is a parasitic elements in all other, just, passive element.Can tuning parasitic loops with in the frequency resonance that allows maximum current in each parasitic loops, to flow, this electric current is created conversely and is arranged in the magnetic field intensity that the interrogation that is parallel to antenna 30 or the plane on antenna 30 needs.As an example, can drive the loop of energy supply with 13.56MHz, and for example can tuning parasitic loops with this fundamental frequency ± frequency resonance of 0.5MHz.

In addition, the non-overlapped concentric loops of antenna 30 can just, form in the simple layer of printed circuit board (PCB) at common plane, is used for being used in the pedestal or the shelf of storage areas 12.Though be described with respect to horizontal level usually, the invention is not restricted to this, and can use differently directional antenna 30 according to specific RFID.

In addition, though the embodiment of Fig. 3 can use other modification to create the field with different distributions as example.For example, can use the combination in any of driving and parasitic loops.In addition, antenna 30 can easily be revised to use one or more different geometric configuratioies, such as parallelogram, and by move, shortening, adjusting angle or drive selected loop, can obtain required electromagnetic field distribution.

Fig. 4 A shows the curve map of the accompanying drawing example in the magnetic field 40,42 that forms by the different driving of selecting antenna 30 and parasitic loops (Fig. 3).Specifically, Fig. 4 A shows along the directions X scanning of storage areas 12 and Y and Z apart from the scanning that keeps constant directions X magnetic field.In this example, use Hewlett Packard model HP 11941A to close a detector (it has the antenna factor), in the amplitude of the 10MHz frequency measurement magnetic field intensity that equals 39dB (uA/m/uV).

Shown in example in, during the interrogation spacing in of outer shroud 32 and interior ring 34 (Fig. 3) energy supply of different number of times, to generate an electromagnetic field 40 and 42 respectively to antenna 30.In whole interval all other in ring as parasitic loops.Shown in example, each drives loop 32,34 and remaining parasitic loops establishment magnetic field 40,42 separately, and its X dimension along antenna 30 demonstrates significant amplitude at difference and reduces.By inquiring cycle selectivity powered loops 32,34, the intensity that can strengthen the field that is produced by antenna 30 keeps below the zone of interrogation in the whole inquiry cycle with the amplitude that reduces the interrogation midfield basically.

Fig. 4 B shows during the loop 32,34 of selectivity energy supply the curve map of amplitude in the magnetic field 40,42 of Fig. 4 A that forms in the inquiry cycle.As shown in the figure, in the inquiry cycle, the loop 32,34 of the selectivity energy supply of antenna 30 and parasitic loops form and have the field 44 of satisfying or surpassing minimum interrogation in being parallel to the interrogation of antenna and on the direction perpendicular to the orientation of the label in the interrogation.

Preferably, antenna 30 can be used for producing and has the amplitude that surpasses the threshold interrogation amplitude in the inquiry cycle, such as the field 44 of 115dBuA/m, with the excitation of the interrogation on entire antenna 30 RFID label basically with provide reliable and communicate by letter.For example, by driving and the parasitic loops of selecting different antenna 30, on the direction of issuable 44 orientation of label in perpendicular to interrogation, for 50%, 75%, 90%, 99% or the more regional threshold interrogation amplitude that surpasses of interrogation.For example, in the inquiry cycle and on the direction perpendicular to the orientation of label, 44 show single inclination angle 46, and wherein amplitude drops to and is lower than example threshold 45.But in this example, 44 drop in a very narrow zone and to be lower than threshold value 45.Specifically, the inclination angle 46 in the field 44 has 0.1 inch or 0.08 inch in threshold value 45, or littler width.By this way, can use antenna 30 to come the more accurate label communication that detects and be associated with article in storage areas 12.

Fig. 4 C provides the view of 3-D view of the magnetic field amplitude of Fig. 4 B.Shown in Fig. 4 C, form in the 44 common interrogation on antenna 30, and surpass threshold value 45 in the essential part of interrogation.In this example, Fig. 4 C shows on the antenna 30 amplitude of the field of measuring in 0.75 inch the interrogation 44.

Fig. 5 is the planimetric map of another exemplary multi-loop antenna 50.Multi-loop antenna 50 comprises and is positioned at many rings of a plurality of layers.More specifically, antenna 50 comprises one group of powered loops 52A-52D (" 52 ") and the parasitic loops 54A-54C (" 54 ") that is positioned at each layer.First group of powered loops 52A and 52B are positioned at top layer and second group of powered loops 52C and 52D are positioned at bottom.The middle layer of parasitic loops 54 between top layer and bottom.Can optionally drive every group of powered loops 52 such as current source with power supply, to create magnetic field.When only driving one of one group of powered loops 52, the loop of other group is as parasitic loops.For the exemplary antenna 30 of Fig. 3, arrange powered loops 52 and the parasitic loops 54 feasible zones that in the whole inquiry cycle, keep below the inquiry threshold value by magnetic field amplitude in the magnetic fields minimizing interrogation of loop generation.

More specifically, the electromagnetic coupled between powered loops 52 and parasitic loops 54 induces the electric current in the parasitic loops 54, and so causes the magnetic field that parasitic loops 54 is associated successively.Magnetic field in the zone that the magnetic field of wherein being created by the combination of powered loops 52 by the further enhancing in the magnetic field of parasitic loops 54 establishments descends.

Though the example of describing in Fig. 5 comprises the loop 52A-52D and the parasitic loops 54A-54C of the energy supply that is positioned at three layers, antenna 50 can comprise the powered loops 52 and the parasitic loops 54 of the arbitrary number of the layer that is positioned at arbitrary number.Antenna 50 can also have the powered loops 52 and the parasitic loops 54 of arranging with a lot of directions, comprises that a part of powered loops 52 is positioned at the layer identical with parasitic loops 54.In addition, can be with structure powered loops 52 of the shape beyond the shape as shown in Figure 5 and parasitic loops 54.

For example, can use constructing antennas 50 on multilayer board arbitrarily in a lot of manufacturing technologies that comprise chemical vapor deposition, sputter, etching, photoetching, mask etc.As selection, can use printing technology with deposit conductive traces on the dielectric layer of printed circuit board (PCB).

Fig. 6 is the decomposition view of the antenna 50 of Fig. 5.As mentioned above, antenna 50 comprises three layers of 56A-56C (" 56 ").For example, layer 56 can be a layer printed circuit board.Layer 56A comprises the loop 52A and the 52B of energy supply, and layer 56B comprises parasitic loops 54A-54C, and layer 56C comprises the loop 52C and the 52D of energy supply.

As mentioned above, can arrange layer 56 with several different modes.For example, layer 56A and 56C can be interchangeable, and a top layer and a layer 56A that feasible layer 56C is antenna 50 are bottoms.In addition, can layer 56 arbitrarily between insert one or more layers.Can also arrange powered loops 52 and parasitic loops 54 in several modes.For example, any one of layer 56 can only comprise and drive loop 52, only comprise parasitic loops 54, perhaps parasitic loops 54 and drive the combination of loop 52.

Fig. 7 is the planimetric map of another exemplary multi-loop antenna 60.Multi-loop antenna 60 comprises the many rings that are positioned at multilayer 62A-62B (" layer 62 ").More specifically, layer 62A comprises a plurality of concentric loops, comprises that at least one powered loops 64 and a plurality of parasitic loops are to strengthen the amplitude of the field at interrogation two ends on antenna 60.Layer 62B comprises additional parasitic loops 66A-66B (" parasitic loops 66 ").Each loop of antenna 60 (parasitic or energy supply) can comprise that the track, circuit of separation or other are suitable for the conductive path that electric current flows.In addition, one or more loops can be made by single, continuous path or circuit.As an example, this loop can be formed by the one or more tracks in the printed circuit board (PCB).

With power drives powered loops 64 to create magnetic field.Other loop of antenna 60, just, the parasitic loops 66 of other loop of layer 62A and layer 62B is used as parasitic loops to strengthen the magnetic field of aforesaid antenna 60.Tuning parasitic loops is with in the frequency resonance that allows maximum current to flow in each parasitic loops, and this electric current is created the essential part of generation for the inquiry plane that is parallel to antenna 60 successively, surpasses the magnetic field intensity that minimum inquiry threshold value needs.

In example as shown in Figure 7, single ring that can this layer of energy supply 62A, for example, outer shroud 64, make the loop of energy supply and remaining parasitic loops on direction, produce the magnetic field of satisfying or surpassing the inquiry threshold value perpendicular to the orientation of the label in the interrogation on the antenna 60.In other words, during the inquiry cycle, do not need the many rings of optionally energy supply to realize the field.Much less, the embodiment of Fig. 7 is used for illustrative purpose, and can the one or more loops of selectivity energy supply or the combination energy supply produce magnetic field to utilize remaining parasitic loops.

Can arrange layer 62 by different way.For example, layer 62A can be the top layer of antenna 60.Alternatively, layer 62A can be the bottom of antenna 60.In addition, can between layer 62A and 62B, insert one or more layers.

Fig. 8 A shows the curve map of the amplitude in the magnetic field 70 of being created by the antenna 60 of Fig. 7.Specifically, Fig. 8 A shows when energy supply outer shroud 64, along the dimension of antenna 60, and the two-dimensional curve figure of the amplitude in the magnetic field of width for example.As shown in the figure, the loop 64 of antenna 60 and remaining parasitic loops form the essential part for the interrogation on antenna 60, have the field 70 of satisfying or surpassing the amplitude of the example threshold value 72 that is used to encourage label.Fig. 8 B shows when energy supply outer shroud 64, the 3-D view of the amplitude in the magnetic field 70 that is produced by antenna 60.

Various embodiments of the present invention has been described.These and other embodiment is below in the scope of claim.

Claims (42)

1. antenna (30,50,60), it comprises a plurality of loops (32 of plane formation each other, 34,52A-D, 54A-C, 64,66), with in the interrogation that is arranged in the plane that is parallel to antenna, produce the electromagnetic field of the radio frequency discrimination RFID that is used for the RFID label, described antenna is directed and makes it be suitable for producing for the essential part of described interrogation the electromagnetic field of the amplitude of the inquiry threshold value that has label (22) at least.

2. antenna as claimed in claim 1, wherein, this loop is directed to produce magnetic field, makes that the amplitude in interrogation satisfies or surpass the inquiry threshold value of label on the direction perpendicular to the orientation of label.

3. antenna as claimed in claim 2, wherein, the first son group of this loop is formed in first printed circuit board (PCB), and the second son group of this loop is formed in second printed circuit board (PCB) with the first printed circuit board (PCB) parallel orientation.

4. antenna as claimed in claim 2, wherein, this loop is formed in the common layer of printed circuit board (PCB).

5. antenna as claimed in claim 1, wherein, the child group of at least two loops in the inquiry cycle by energy supply optionally to realize magnetic field.

6. antenna as claimed in claim 1, wherein, this loop comprises loop and at least one parasitic loops of at least one energy supply.

7. antenna as claimed in claim 1, wherein, this antenna be embedded in vertical file pedestal (12C, 12D) in or shelf (12A, 12B) in.

8. antenna as claimed in claim 1, wherein, this loop comprises concentric loops.

9. antenna as claimed in claim 7, wherein, this antenna comprises at least three concentric loops.

10. antenna as claimed in claim 7, wherein, this antenna comprises at least ten five concentric loops.

11. antenna as claimed in claim 1, wherein, this loop is included in multilayer (56A-C, 62A-B) the middle a plurality of plane loop that form of printed circuit board (PCB).

12. antenna as claimed in claim 11, wherein, these a plurality of plane loop are included in the one or more powered loops in the top layer, the one or more powered loops in bottom, and the one or more parasitic loops in the layer between top layer and bottom.

13. antenna as claimed in claim 1, wherein, the electromagnetic field that should be formed by antenna is at least 50% of described interrogation, above the threshold amplitude that is used to encourage RFID tag.

14. antenna as claimed in claim 1, wherein, the electromagnetic field that should be formed by antenna is at least 75% of described interrogation, above the threshold amplitude that is used to encourage RFID tag.

15. antenna as claimed in claim 1, wherein, the electromagnetic field that should be formed by antenna is at least 90% of described interrogation, above the threshold amplitude that is used to encourage RFID tag.

16. a radio-frequency recognition system (10), it comprises:

Storage area (12A-12E), its storage have the article of the radio frequency identification (RFID) labels (22) that is associated, and described label has the inquiry threshold value;

Antenna (30,50,60), it is near storage area, comprise a plurality of loops that plane each other forms (32,34,52A-D, 54A-C, 64,66), be used for producing the electromagnetic field of the radio-frequency (RF) identification of RFID tag in the interrogation that is arranged in the plane that is parallel to antenna; And

RFID reader (12E), the coupling of itself and antenna be with at least one loop of energy supply antenna optionally, and not energy supply residue loop to be communicating by letter with RFID tag,

Wherein this electromagnetic field has the amplitude of the inquiry threshold value of label at least for the essential part of the interrogation that is arranged in the plane that is parallel to antenna.

17. system as claimed in claim 16, wherein, this antenna comprises at least one powered loops and at least one parasitic loops.

18. system as claimed in claim 16, wherein, this antenna comprises concentric loops.

19. system as claimed in claim 16, wherein, this antenna is included in the loop that forms in the common plane.

20. system as claimed in claim 16, wherein, this antenna is included in the loop that forms on the simple layer of printed circuit board (PCB).

21. system as claimed in claim 16, wherein, this antenna is embedded in the storage area.

22. system as claimed in claim 16, wherein, this antenna is included in multilayer (56A-C, 62A-B) the middle a plurality of plane loop that form of printed circuit board (PCB).

23. system as claimed in claim 16, wherein, this RFID reader during the inquiry cycle with at least two loops of different selection of times ground energy supply antenna.

24. system as claimed in claim 16 further comprises file tracker (14), it receives information and canned data database from RFID reader.

25. system as claimed in claim 24 further comprises remote computer, the coupling of itself and file tracker is with to long-distance user's presentation information.

26. system as claimed in claim 16, wherein, this storage area comprises at least one of shelf unit, cabinet, vertical file separator, intelligent vehicle and desktop type reader.

27. system as claimed in claim 16, wherein, the information that receives from RFID tag comprises the positional information of the article that are used for storage area.

28. system as claimed in claim 16, wherein, the article with the RFID tag that is associated comprise at least one of file and document.

29. a method, it comprises:

Provide the antenna with a plurality of loops that plane each other forms with in the interrogation that is arranged in the plane that is parallel to antenna, produce the electromagnetic field of the radio frequency discrimination RFID that is used for the RFID label, described RFID label has the inquiry threshold value,

Optionally the energy supply multi-loop antenna (30,50,60) at least one loop (32,34,52A-D, 54A-C, 64,66) and the remaining loop of not energy supply near storage area (12A-12E), to generate an electromagnetic field during the inquiry cycle, wherein electromagnetic field has the amplitude of the inquiry threshold value of label at least for the essential part of the interrogation that is arranged in the plane that is parallel to antenna; With

One or more RFID tag (22) acquired information of the article during the inquiry cycle from be fixed to storage area.

30. method as claimed in claim 29, wherein, the step of this energy supply multi-loop antenna is included in during the inquiry cycle the two or more loops with different selection of times ground energy supply multi-loop antennas, with essential part, produce the electromagnetic field of the amplitude of the inquiry threshold value that has label at least for the interrogation that is arranged in the plane that is parallel to antenna.

31. method as claimed in claim 29, wherein, the step of this energy supply multi-loop antenna comprises one or more loops of energy supply multi-loop antenna with on the direction perpendicular to the label orientation, produces the electromagnetic field of the amplitude with the inquiry threshold value that satisfies or surpass label.

32. method as claimed in claim 29 further is included in the information of storing in the database from RFID tag.

33. method as claimed in claim 29 further comprises to the long-distance user presenting information from label.

34. method as claimed in claim 29, wherein, comprise the positional information of the article that obtain to have fixed RFID tag from the step of RFID tag acquired information of excitation, and in addition wherein these article comprise one of books, file and document of being arranged in storage area.

35. method as claimed in claim 29, wherein, this multi-loop antenna comprises at least one powered loops and at least one parasitic loops, and the loop that the step of energy supply multi-loop antenna further comprises optionally this energy supply of energy supply with create electromagnetic field and by with the induction current in parasitic loops that intercouples of powered loops, to influence electromagnetic field distribution.

36. method as claimed in claim 29, wherein, the step of this energy supply multi-loop antenna further comprises:

First of the powered loops son group is to create first electromagnetic field during the first in inquiry cycle; And

The second son group of powered loops to be creating second electromagnetic field during the second portion in inquiry cycle,

Wherein, the effect of this first and second electromagnetic field is created in the electromagnetic field of amplitude that the inquiry cycle has the inquiry threshold value of label at least.

37. method as claimed in claim 36, wherein, first and second parts in this inquiry cycle are non-overlapped.

38. method as claimed in claim 36, wherein, the first son group and the second son group of this loop are arranged in common plane.

39. method as claimed in claim 36, wherein, the first son group of this loop and second son organize be positioned at multilayer (56A-C, 62A-B) in.

40. method as claimed in claim 30, wherein, the amplitude of this electromagnetic field surpasses the threshold amplitude that is used to encourage RFID tag at least 50% of described interrogation.

41. method as claimed in claim 30, wherein, the amplitude of this electromagnetic field surpasses the threshold amplitude that is used to encourage RFID tag at least 75% of described interrogation.

42. method as claimed in claim 30, wherein, the amplitude of this electromagnetic field surpasses the threshold amplitude that is used to encourage RFID tag at least 90% of described interrogation.

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