Source: http://www.google.com/patents/US7750792?ie=ISO-8859-1&dq=6,563,928
Timestamp: 2014-03-16 21:34:32
Document Index: 168645183

Matched Legal Cases: ['Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60']

Patent US7750792 - Multi-mode tags and methods of making and using the same - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsMulti-mode (e.g., EAS and RFID) tags and methods for making and using the same are disclosed. The tag generally includes an antenna, an electronic article surveillance (EAS) function block coupled to the antenna, and one or more identification function blocks coupled to the antenna in parallel with the...http://www.google.com/patents/US7750792?utm_source=gb-gplus-sharePatent US7750792 - Multi-mode tags and methods of making and using the sameAdvanced Patent SearchPublication numberUS7750792 B2Publication typeGrantApplication numberUS 11/870,775Publication dateJul 6, 2010Filing dateOct 11, 2007Priority dateOct 11, 2006Also published asCA2672915A1, EP2082382A2, EP2082382A4, EP2082382B1, US20080088417, US20100231362, WO2008045570A2, WO2008045570A3, WO2008045570B1Publication number11870775, 870775, US 7750792 B2, US 7750792B2, US-B2-7750792, US7750792 B2, US7750792B2InventorsPatrick Smith, James Montague Cleeves, Vikram Pavate, Vivek SubramanianOriginal AssigneeKovio, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (32), Non-Patent Citations (1), Referenced by (8), Classifications (19), Legal Events (1) External Links: USPTO, USPTO Assignment, EspacenetMulti-mode tags and methods of making and using the sameUS 7750792 B2Abstract Multi-mode (e.g., EAS and RFID) tags and methods for making and using the same are disclosed. The tag generally includes an antenna, an electronic article surveillance (EAS) function block coupled to the antenna, and one or more identification function blocks coupled to the antenna in parallel with the EAS function block. The method of reading the tag generally includes the steps of applying an electric field to the tag, detecting the tag when the electric field has a relatively low power, and detecting an identification signal from the tag when the electric field has a relatively high power. The present invention advantageously enables a single tag to be used for both inventory and anti-theft purposes, thereby improving inventory management and control at reduced system and/or �per-article� costs.
b) an electronic article surveillance (EAS) function block coupled to the antenna;
c) one or more RFID function blocks coupled to the antenna in parallel with the EAS function block; and
d) a rectifier configured to become (i) substantially disabled in an electric field having an energy below a first predetermined threshold and (ii) substantially enabled when the energy of the electric field is above a second predetermined threshold, the second threshold being greater than or equal to the first threshold;
wherein (i) the tag has a high Q state in the electric field having an energy below the first predetermined threshold, and (ii) the tag has a low Q state in the electric field having an energy above the second predetermined threshold.
2. The multi-mode identification tag of claim 1, wherein the rectifier is coupled to the antenna in parallel with the EAS function block.
3. The multi-mode identification tag of claim 1, wherein the rectifier is coupled to the antenna in parallel with the EAS function block, and the rectifier is substantially non-operational or disabled when the tag has the high Q state, and the rectifier is operational or enabled when the tag has the low Q state.
4. The multi-mode identification tag of claim 1, wherein the RFID function block(s) are substantially non-operational, disabled or electrically disconnected from a power supply when the tag has the high Q state, and the RFID function block(s) are substantially operational, enabled or electrically connected to the power supply when the tag has the low Q state.
5. The multi-mode identification tag of claim 4, wherein when the tag is in the low Q state, the tag is unreadable and the EAS function is non-operational.
6. The multi-mode identification tag of claim 1, wherein when the electric field has a power above the first predetermined threshold, a sufficient number of the RFID function block(s) are enabled or electrically connected to the power supply to lower the Q of the tag to the low Q state.
7. The multi-mode identification tag of claim 6, wherein when the power of the electric field is below the second predetermined threshold, a sufficient number of the RFID function block(s) are disabled or electrically disconnected from the power supply to maintain the Q of the tag in the high Q state.
8. The multi-mode identification tag of claim 1, wherein the rectifier has a resonating circuit with a load effective to reduce the Q of the tag.
10. The multi-mode identification tag of claim 9, wherein the programmable threshold device comprises a thin film transistor.
11. The multi-mode identification tag of claim 10, wherein the thin film transistor has a threshold sufficiently low to maintain the tag in a low Q state until the tag is removed from the electric field.
12. The multi-mode identification tag of claim 10, wherein the tag includes logic configured to change the threshold of the thin film transistor to a relatively high value so that the antenna enters a high Q state.
13. The multi-mode identification tag of claim 1, wherein the rectifier receives a signal having a characteristic frequency from the antenna and provides upper and lower power supplies to the RFID function block(s).
14. The multi-mode identification tag of claim 1, wherein the RFID function block(s) comprise a demodulator or clock extractor configured to receive a signal from the antenna and provide a clock signal to remaining RFID function block(s) in response thereto.
15. The multi-mode identification tag of claim 14, wherein the RFID function block(s) further comprise logic configured to receive the clock signal from the demodulator or clock extractor and provide an identification signal in response thereto.
16. The multi-mode identification tag of claim 15, wherein the logic comprises a memory storing a bit string, and the identification signal comprises the bit string.
17. The multi-mode identification tag of claim 16, wherein the logic is configured to silence the tag for a period of time and re-transmit the bit string thereafter.
18. The multi-mode identification tag of claim 15, wherein the RFID function block(s) further comprise a modulator or output stage configured to transmit the identification signal or a modulated identification signal to the antenna.
19. The multi-mode identification tag of claim 1, wherein the EAS function block comprises a capacitor.
20. The multi-mode identification tag of claim 19, wherein the capacitor has a predetermined breakdown voltage.
21. The multi-mode identification tag of claim 1, wherein the antenna comprises a coil and a tuning element.
22. The multi-mode identification tag of claim 21, wherein the tuning element comprises a second coil, a capacitor or capacitor plate, or a tuning ring.
23. The multi-mode identification tag of claim 1, wherein the EAS function block comprises a capacitor.
24. The multi-mode identification tag of claim 23, wherein the capacitor has a characteristic breakdown voltage in the range from about 10 to about 40 V.
25. A method of reading an identification tag, comprising:
a) applying an electric field to the tag, wherein (i) the tag has a high Q state in an electric field having an energy below a first predetermined threshold, and (ii) the tag has a low Q state in an electric field having an energy above a second predetermined threshold, the tag further having a rectifier configured to become (i) substantially disabled when the electric field has an energy below the first predetermined threshold and (ii) substantially enabled when the energy of the electric field is above the second predetermined threshold, the second threshold being greater than or equal to the first threshold;
b) detecting the tag when the energy of the electric field is below the first threshold and the tag has the high Q state; and
c) detecting an identification signal from the tag when the energy of the electric field is above the second threshold and the tag has the low Q state.
26. The method of claim 25, wherein the tag comprises one or more RFID function block(s) that are substantially non-operational, disabled or electrically disconnected from a power supply when the tag has the high Q state, and the RFID function block(s) are substantially operational, enabled or electrically connected to the power supply when the tag has the low Q state.
27. The method of claim 26, wherein when the energy of the electric field is above the second predetermined threshold, a sufficient number of the RFID function block(s) are enabled or electrically connected to the power supply to lower the Q of the tag to the low Q state.
28. The method of claim 27, wherein when the energy of the electric field is below the first predetermined threshold, a sufficient number of the RFID function block(s) are disabled or electrically disconnected from the power supply to maintain the Q of the tag in the high Q state.
29. The method of claim 25, wherein the programmable threshold device comprises a thin film transistor having a threshold sufficiently low to maintain the tag in a low Q state until the tag is removed from the electric field.
30. The method of claim 29, wherein the tag includes logic configured to change the threshold of the thin film transistor to a relatively high value so that the antenna enters a high Q state. Description
RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 60/851,122, filed Oct. 11, 2006, and U.S. Provisional Application No. 60/880,827, filed Jan. 16, 2007, both of which are incorporated herein by reference in their entireties.
FIELD OF THE INVENTION The present invention generally relates to EAS (electronic article surveillance) and/or RFID (radio frequency identification) tags. More specifically, embodiments of the present invention pertain to multi-mode (e.g., �dual use� tags, having EAS and RFID functions thereon, for example) tags and methods for making and using the same.
DISCUSSION OF THE BACKGROUND As is known in the art, EAS tags are useful for anti-theft detection, but generally do not store enough information for inventory control. On the other hand, RFID tags typically do not have an operational range sufficient for anti-theft uses, since they typically need to be within a short distance of the reader to obtain sufficient power to operate. It would be useful and/or desirable if a single tag could have both sufficient circuitry on-board for inventory control and/or �smart card� operations (e.g., auto toll tags, employee identification/security cards, etc.), while also having an EAS circuit with an operational range sufficient for compatibility with present EAS systems.
SUMMARY OF THE INVENTION Embodiments of the present invention relate to dual use or multi-mode (e.g., EAS and RFID) identification tags and methods for making and using the same. The multi-mode identification tag generally comprises an antenna, an electronic article surveillance (EAS) function block coupled to the antenna, and one or more RFID function blocks coupled to the antenna in, thus enabling operation of the tag in both EAS and RFID modes. The invention may further relate to systems adapted to use multi-mode tags embodying one or more of the inventive concepts disclosed herein.
FIG. 1 shows a first exemplary embodiment of a suitable dual-mode tag architecture 100. The architecture 100 includes an antenna 110, an EAS function block 120, and an RFID portion 170 (e.g., as described in U.S. patent application Ser. Nos. 11/544,366 and 11/595,839, filed on Oct. 6, 2006 and Nov. 8, 2006, respectively, the relevant portions of which are incorporated herein by reference). The EAS function block 120 is coupled to the antenna 110 in parallel with part or all of the RFID block 170 (e.g., RF→DC rectifier block 180, logic 150, and modulator 140, which may be in series as shown in FIG. 1). /In one embodiment, the EAS function block may comprise a linear and/or non-linear capacitor, as described in U.S. Pat. No. 7,152,804 and/or U.S. patent application Ser. No. 11/104,375, filed Apr. 11, 2005, the relevant portions of which are incorporated herein by reference. Each of the functional blocks in FIG. 1 is largely known in the art, and unless otherwise described or claimed herein, is as known in the art.
In further embodiments, RFID block 170 may further comprise a demodulator/clock generator block 130 (e.g., in parallel with the rectifier 180) and/or memory 160 (which may contain programming and/or configuration information for logic and/or I/O control block 150). In alternative embodiments, RF→DC rectifier block 180 can be substituted by a very high frequency (VHF)→DC rectifier block or an ultrahigh frequency (UHF)→DC rectifier block (see, e.g., U.S. patent application Ser. Nos. 11/595,839 and 11/544,366, the relevant portions of which are incorporated herein by reference).
However, in practice, such tags generally operate at frequencies below 50 MHz, due to certain technological limits. The reader should be designed for a chosen or predetermined frequency (e.g., 13.56 MHz), and the tag may include a divider (e.g., in demodulator/clock function block 130 in FIG. 1) to generate an internal (e.g., on-tag) clock signal. Thus, in one embodiment, a chip designed to provide a 106 KHz clock at 13 MHz applied power can provide a �65 KHz clock at 8 MHz applied power.
The present tag is not limited, however, to divided clock architectures. For example, at UHF frequencies, the clock may be a modulated signal on the UHF carrier, and may thus be demodulated to obtain the necessary clock signal for the tag (see, e.g., the tag architecture of FIG. 1, which may also be suitable for HF frequencies, depending on the design of the antenna; see e.g., U.S. patent application Ser. Nos. 11/544,366 and 11/595,839, filed on Oct. 6, 2006 and Nov. 8, 2006, respectively). For example, a 200 kHz clock could be modulated onto a 900 MHz carrier signal. The use of a modulated clock would allow the carrier frequency to be changed while keeping the data rate fixed (provided the modulated signal stayed unchanged).
A mechanism for preserving a high Q in a combination RFID/EAS tag where the EAS mode functions at long ranges (e.g., >10 cm) and the RFID mode functions at short ranges (e.g., <5 cm, where the available power is larger) may include a rectifier on the dual-mode RFID chip which has a moderately high threshold of operational voltage. Thus, in such an embodiment, the dual-mode chip does not draw any significant power as long as the AC voltage on the coil is small (e.g., below a certain or predetermined threshold), thereby preserving the high Q for EAS operation. When the AC voltage on the coil exceeds the threshold (which may be selectable, programmable, tunable, etc.), the chip rectifier turns on, reducing the Q of the multi-mode tag while supplying power to run the RFID mode of the chip. This may be implemented by using a diode chain to control the turn-on threshold of the diode-wired transistors in the rectifier (see, e.g., U.S. Provisional Patent Application No. 60/749,121, filed Dec. 7, 2005, and U.S. patent application Ser. No. 11/521,924, filed Sep. 15, 2006, the relevant portions of which are incorporated herein by reference). Such a design generally uses a diode chain circuit similar to a voltage-controlled shunt.
An additional variation may include tuning the tag such that when the rectifier is not powered up or operational, the operating frequency may be one value, but then when the tag (or rectifier) powers up, an on-tag capacitance may change to allow it to operate efficiently at a different frequency (see, e.g., U.S. Provisional Patent Application No. 60/592,596, filed Jul. 31, 2004, and U.S. patent application Ser. No. 11/104,375, filed Apr. 11, 2005, the relevant portions of which are incorporated herein by reference).
In an alternative embodiment, detection in EAS mode may be achieved by using the reader to send two separate signals at different frequencies, and exploiting the nonlinearity of the tag to mix the two signals. Detection could be achieved by monitoring for the presence of sidebands on the higher frequency signal sent by the reader (see, e.g., U.S. patent application Ser. No. 11/104,375, filed Apr. 11, 2005, the relevant portions of which are incorporated herein by reference). For example, the reader can send signals at 900 MHz and 100 kHz, and in the presence of a tag, sidebands would be created at 900.1 MHz and 899.9 MHz. In the absence of a tag, no such sidebands exist.
A mechanism for preserving a high Q in a combination RFID/EAS tag where the EAS mode functions at long ranges (e.g., >10 cm) and the RFID mode functions at short ranges (e.g., <5 cm) where the available power is larger, may include a rectifier (see, e.g., the rectifier 425 in the exemplary EAS circuit 400 of FIG. 4) on the dual-mode RFID chip. The rectifier may have a moderately high threshold of operational voltage. Thus, in such an embodiment, the dual-mode chip does not draw significant power as long as the AC voltage on the coil is small (e.g., below a certain or predetermined threshold), thereby preserving the high Q for EAS operation. When the AC voltage on the coil exceeds the threshold (which may be selectable, programmable, tunable, etc.), the chip rectifier turns on, reducing the Q of the combination tag while supplying power to run the RFID mode of the chip. This may be implemented using a diode chain 420 (e.g., series-connected diodes 422 and 424) to control the turn-on threshold of diode-wired transistors in the rectifier 400 (see, e.g., U.S. Provisional Patent Application No. 60/749,121, filed Dec. 7, 2005, and U.S. patent application Ser. No. 11/521,924, filed Sep. 15, 2006, the relevant portions of which are incorporated herein by reference). Such a design uses the diode chain circuit (e.g., series-linked diode chain 420) similarly to a voltage-controlled shunt. Alternatively, the diode-wired transistors (e.g., 422 and 424) may be replaced with true diodes (e.g., Schottky diodes, as disclosed in U.S. Pat. No. 7,152,804, the relevant portions of which are incorporated herein by reference) to reduce the circuit size or to allow the rectifier (and therefore the high-Q/low-Q switching) to operate at higher frequencies (UHF, for example). In further embodiments, one may include more than 2 transistors or diodes (especially if they are Schottky-type diodes rather than diode-wired transistors) in series to control the turn-on threshold of the rectifier 400.
As is taught in U.S. patent application Ser. No. 11/104,375, the relevant portions of which are incorporated herein by reference), two antennae in close proximity can cause either or both of the antennae to act differently than they would independently. Two different antenna on the same inlay (or tag) can be configured or tuned such that each antenna acts as designed to for an intended function (e.g., one antenna for EAS operation[s], a second for RFID operation[s]). In one embodiment, an 8 MHz antenna/fixed capacitor combination may provide the EAS function on the same tag as a 13 MHz antenna connected to the logic circuitry. HF and UHF antennae can also be similarly combined.
FIG. 6 shows another exemplary embodiment 600 for using the present multi-mode tag. Like in FIG. 5, identification information may be programmed into the memory (e.g., 160 in FIG. 1) of a multi-mode tag in step 604. If the tag is in an electromagnetic (EM) field of sufficient strength to activate part or all of the RFID circuitry on the tag, then the identification information on the tag can be read in step 606 (FIG. 6). If not, an indicator or flag can be set (e.g., in the reader) to wait a predetermined period of time until a characteristic EAS delay expires (step 608).
Exemplary RFID Operations
RFID operations at 8.2 MHz are possible using the multi-mode tag 100. One exemplary RFID block 270 can include or be based on an RFID device having a predetermined number of bits (e.g., 2 or more bits, such as from m*2n, where m and n are independently integers of at least 1, and at least one of m and n is at least 2; in one embodiment, m*2n is 96 bits) in memory 160 and that may be capable of operating in the 13.56 MHz frequency band. In a preferred embodiment, memory 160 comprises a ROM (e.g., fuse bank, mask-programmable ROM, or EPROM). In some of these embodiments, the functional operation of the RFID block or portion 170 of the tag at 13.56 MHz can be used independent of the multi-mode operations of the device 100.
The exemplary tag 100 may transmit a ((m*2n)/p)-bit code, where p is an integer of 1 or more (in one embodiment, 1), on absorbing sufficient power as it enters the reader's 13.56 MHz RF field. A simple TTF (tags talk first) anti-collision scheme can be implemented thereon, which allows several tags in the reader's field to be differentiated (see, e.g., U.S. Provisional Patent Application No. 60/748,973, filed Dec. 7, 2005, and U.S. patent application Ser. No. 11/544,366, filed Oct. 6, 2006, the relevant portions of which are incorporated herein by reference, for an example of such a scheme.
Although RFID tags are generally designed to operate at 13.56 MHz, the RFID portion 170 of the dual mode tag 100 can be operated at 8.2 MHz simply by retuning the resonant frequency (see, e.g., U.S. patent application Ser. No. 11/104,375, filed Apr. 11, 2005, the relevant portions of which are incorporated herein by reference). Retuning can also be done by changing the antenna inductance and/or the on-chip tuning capacitor value, as disclosed in U.S. patent application Ser. No. 11/104,375.
Power Availability at 8.2 MHz
The Federal Communications Commission (FCC) limits the magnetic field strength provided by the carrier at 8.2 MHz to only 1% of that at 13.56 MHz (i.e., 0.1 mV/m at 30 m for 8.2 MHz, vs. 10 mV/m at 30 m for 13.56 MHz). Converting this to a near-field magnetic field, the maximum permissible field strength at 3 cm would be about 10 A/m at 8.2 MHz, but 365 A/m at 13.56 MHz. However, by pulsing the 8.2 MHz carrier at a 10� peak power and a 10% duty cycle, short bursts (e.g., a maximum pulse length of about 12 nsec or less) can reach 100 A/m. Equivalent pulse lengths and power increases can be easily determined by one skilled in the art, in accordance with design and/or application choices.
Exemplary EAS Functionality
Combining the exemplary RFID block 170 with technology compatible with existing 8.2 MHz EAS systems, without affecting existing EAS system operation, presents two hurdles for the present dual-mode tag 100. First, the RFID portion 170 of the RFID/EAS tag 100 must be readable (e.g., at retail checkouts) without interfering with EAS deactivation or causing inadvertent deactivation. Second, the functionality of RFID block 170 should not interfere with EAS detection; i.e., RFID functionality should operate orthogonally to the EAS function(s) 120.
FIG. 2 shows a second exemplary embodiment of a dual-mode tag architecture 200 suitable for use in the present invention. As for the embodiment of FIG. 1, the dual-mode tag 200 includes an antenna (not shown, but represented by the Coil1/Coil2 terminals), an EAS function block 220, a full wave rectifier 202, and an RFID portion 270 (described in U.S. patent application Ser. Nos. 11/521,924, 11/544,366 and 11/595,839, filed on Sep. 15, 2006, Oct. 6, 2006 and Nov. 8, 2006, respectively, the relevant portions of which are incorporated herein by reference). Also similarly to FIG. 1, the EAS function block 220 is coupled to the antenna (or across terminals thereto) in parallel with RFID portion 270 and/or full wave rectifier 202.
FIGS. 3A-3B show exemplary embodiments of dual-mode tag architectures, the RFID portion(s) of which are described in U.S. patent application Ser. Nos. 11/544,366 and 11/595,839, filed on Oct. 6, 2006 and Nov. 8, 2006, respectively, the relevant portions of which are incorporated herein by reference. These dual-mode architectures further include an EAS function block 320 (FIG. 3A) or 370 (FIG. 3B) coupled to the antenna 302 (FIG. 3A) or 352 (FIG. 3B) or across terminals thereto. The EAS function block 320 or 370 may comprise a linear and/or non-linear capacitor, as described in U.S. Pat. No. 7,152,804 and/or U.S. patent application Ser. No. 11/104,375, filed Apr. 11, 2005, the relevant portions of which are incorporated herein by reference, and function similarly to EAS function block 120/220 above (see also FIGS. 1-2).
The antenna 302 may be implemented using a resonant LC circuit for use at 13.56 MHz, for example, but tunable for use at, e.g., 8.2 MHz (i.e., at a frequency typical of EAS applications). Alternatively, the antenna may be implemented using a dipole or similar such antenna for 900 MHz (high frequency, or HF) operation or 2.4 GHz (very high frequency, or VHF) operation. Generally, the antenna may be used to provide power for operation of the tag circuitry, and to provide information from the tag to the reader or interrogator. Using power-up circuit 304, power can be extracted by rectifying the RF signal collected by antenna 302 and storing the resultant charge in a storage capacitor (e.g., CS). Thus, when a tag enters a region of space with sufficient electromagnetic field being transmitted from a nearby reader, the capacitor begins to charge-up, and a voltage across the capacitor increases accordingly. When the voltage reaches a sufficient value, an �enable� signal can be generated, and this enable signal (e.g., EN) can be used to initiate circuit operation (e.g., by coupling to clock 306 and counter 308).
FIG. 4 shows an exemplary EAS block 400 for use in the present multi-mode tags. EAS block 400 may include a rectifier 425 and a capacitor block 440. In one embodiment, capacitor block 440 comprises series capacitors 442 and 444, which receive the external signal (e.g., an 8.2 MHz RF/EAS signal) from antenna 410 and which are configured to provide the EAS deactivation function. Bridge rectifier 425 may comprise four series-connected diode pairs (e.g., 420, comprising first diode 422 and second diode 424; see, e.g., U.S. patent application Ser. No. 11/521,924, filed Sep. 15, 2006, the relevant portions of which are incorporated herein by reference) as shown in FIG. 4. Alternatively, the rectifier may comprise a half-wave rectifier (e.g., diode pair 420) or a full-wave rectifier (e.g., two series-connected diode pairs, such as diode pair 420 and its complement between Vin′ and Vout). Series-connected devices such as diodes 422 and 424 and capacitors 442 and 444, and methods of making the same, are described in U.S. Provisional Patent Application No. 60/859,480, filed Nov. 15, 2006, the relevant portions of which are incorporated herein by reference. Load 430 across power supply VOUT/VOUT′ generally comprises a conventional load resistor.
A further aspect of the invention relates to a method of making the present multi-mode (e.g., dual-use) tag. Advantageously, the present tag may be manufactured using printing technology, rather than photolithography. Such a manufacturing approach minimizes waste of materials and increases throughput, relative to photolithographic processes. Suitable printing processes for forming patterned layers of (doped) silicon, metal, and insulator can be found in U.S. Pat. No. 7,152,804 and and U.S. patent application Ser. Nos. 11/243,460, 11/104,375, 11/452,108, filed Oct. 3, 2004, Apr. 5, 2005, Jun. 12, 2006, Oct. 6, 2006, respectively, the relevant portions of each of which is incorporated by reference herein.
An existing 13 MHz tag, connected to an antenna tuned to 8 MHz, can function as an RFID tag close to a reader and as an EAS tag at a distance from the reader, as demonstrated by simulation as well as by measurements taken on RFID tag circuitry designed for operation at 13.56 MHz, but tested at 8 MHz. A rectifier circuit with a voltage-controlled turn-on has been designed (see, e.g., U.S. patent application Ser. No. 11/521,924) and fabricated using Si ink technology (see, e.g., U.S. patent application Ser. Nos. 10/789,317, 10/949,013, 10/950,373, and 10/956,714, filed on Feb. 27, 2004, Sep. 24, 2004, Sep. 24, 2004, and Oct. 1, 2004 respectively and an externally attached capacitor. The rectifier circuit is configured to prevent the RFID circuitry from affecting the EAS operation at a distance. The 8.2 MHz EAS mode antenna resonated strongly enough to be detected by a commercially available EAS reader (from Checkpoint Systems), and it also showed that bits in a programmed memory are clocked out when the tag is in a higher field region (e.g., representative of or simulating an RFID field). The RFID circuitry did not affect the EAS operation at a distance.
CONCLUSION/SUMMARY Thus, the present invention provides a multi-mode identification tag and methods for making and reading the same. The tag generally comprises an antenna, an electronic article surveillance (EAS) function block coupled to the antenna, and one or more RFID function blocks coupled to the antenna in parallel with the EAS function block. The method of reading an identification tag generally comprises applying an electric field to the tag, detecting the tag when the electric field has a relatively low power, and detecting an identification signal from the tag when the electric field has a relatively high power. In the present method, the electric field is typically generated by a tag reader. Thus, embodiments of the present invention advantageously provide the tag with both an EAS function and a RFID function. Thus, the tag is useful as an RFID tag, at least before the EAS function is disabled. As a result, manufacturers, wholesalers, distributors and retailers can use a single tag for RF and EAS functions, thereby simplifying product and inventory management and potentially reducing the costs of performing and/or providing both functions.
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