Patent Application
20070273481
The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention.
The present invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. Additionally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears.
Methods, systems, and apparatuses for RFID devices are described herein. In particular, methods, systems, and apparatuses for controlling tag responses to RFID communication signals are described.
In an embodiment, RFID tags monitor a strength of signals transmitted by RFID readers. For example, a reader transmits a signal to a tag to power the tag. The tag measures a strength of the received signal. The reader transmits a read signal to the tag. The tag responds to the read signal if the measured strength of the received signal meets desired criteria.
Embodiments of the present invention aid in overcoming security issues, enabling tags to respond to read signals transmitted by readers within a desired communication range. The range of the reader transmitting the read signal correlates to strength (e.g., power level) of the power signal provided by the reader. Thus, if the measured signal strength is sufficient, and/or satisfies other criteria, the tag responds to the read signal. The particular data transmitted by the tag may depend on a particular measured signal strength.
The present specification discloses one or more embodiments that incorporate the features of the invention. The disclosed embodiment(s) merely exemplify the invention. The scope of the invention is not limited to the disclosed embodiment(s). The invention is defined by the claims appended hereto.
References in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.
Furthermore, it should be understood that spatial descriptions (e.g., “above,” “below,” “up,” “left,” “right,” “down,” “top,” “bottom,” “vertical,” “horizontal,” etc.) used herein are for purposes of illustration only, and that practical implementations of the structures described herein can be spatially arranged in any orientation or manner. Likewise, particular bit values of “0” or “1” (and representative voltage values) are used in illustrative examples provided herein to represent data for purposes of illustration only. Data described herein can be represented by either bit value (and by alternative voltage values), and embodiments described herein can be configured to operate on either bit value (and any representative voltage value), as would be understood by persons skilled in the relevant art(s).
Before describing embodiments of the present invention in detail, it is helpful to describe an example RFID communications environment in which the invention may be implemented.
Environment 100 includes any number of one or more readers 104. For example, environment 100 includes a first reader 104a and a second reader 104b. Readers 104a and/or 104b may be requested by an external application to address the population of tags 120. Alternatively, reader 104a and/or reader 104b may have internal logic that initiates communication, or may have a trigger mechanism that an operator of a reader 104 uses to initiate communication. Readers 104a and 104b may also communicate with each other in a reader network.
As shown in
Various types of tags 102 may be present in tag population 120 that transmit one or more response signals 112 to an interrogating reader 104, including by alternatively reflecting and absorbing portions of signal 110 according to a time-based pattern or frequency. This technique for alternatively absorbing and reflecting signal 110 is referred to herein as backscatter modulation. Readers 104a and 104b receive and obtain data from response signals 112, such as an identification number of the responding tag 102. In the embodiments described herein, a reader may be capable of communicating with tags 102 according to any suitable communication protocol, including Class 0, Class 1, EPC Gen 2, other binary traversal protocols and slotted aloha protocols, any other protocols mentioned elsewhere herein, and future communication protocols.
Baseband processor 212 and network interface 216 are optionally present in reader 104. Baseband processor 212 may be present in reader 104, or may be located remote from reader 104. For example, in an embodiment, network interface 216 may be present in reader 104, to communicate between transceiver portion 220 and a remote server that includes baseband processor 212. When baseband processor 212 is present in reader 104, network interface 216 may be optionally present to communicate between baseband processor 212 and a remote server. In another embodiment, network interface 216 is not present in reader 104.
In an embodiment, reader 104 includes network interface 216 to interface reader 104 with a communications network 218. As shown in
Reader 104 has at least one antenna 202 for communicating with tags 102 and/or other readers 104. Antenna(s) 202 may be any type of reader antenna known to persons skilled in the relevant art(s), including a vertical, dipole, loop, Yagi-Uda, slot, or patch antenna type. For description of an example antenna suitable for reader 104, refer to U.S. Ser. No. 11/265,143, filed Nov. 3, 2005, titled “Low Return Loss Rugged RFID Antenna,” now pending, which is incorporated by reference herein in its entirety.
Transceiver 220 receives a tag response via antenna 202. Transceiver 220 outputs a decoded data signal 214 generated from the tag response. Network interface 216 is used to transmit decoded data signal 214 received from transceiver portion 220 (optionally through baseband processor 212) to a remote server coupled to communications network 218. Baseband processor 212 optionally processes the data of decoded data signal 214 prior to being sent over communications network 218.
In embodiments, network interface 216 enables a wired and/or wireless connection with communications network 218. For example, network interface 216 may enable a wireless local area network (WLAN) link (including a IEEE 802.11 WLAN standard link), a BLUETOOTH link, and/or other types of wireless communication links. Communications network 218 may be a local area network (LAN), a wide area network (WAN) (e.g., the Internet), and/or a personal area network (PAN).
In embodiments, a variety of mechanisms may be used to initiate an interrogation request by reader 104. For example, an interrogation request may be initiated by a remote computer system/server that communicates with reader 104 over communications network 218. Alternatively, reader 104 may include a finger-trigger mechanism, a keyboard, a graphical user interface (GUI), and/or a voice activated mechanism with which a user of reader 104 may interact to initiate an interrogation by reader 104.
In the example of
Modulator/encoder 208 receives interrogation request 210, and is coupled to an input of RF front-end 204. Modulator/encoder 208 encodes interrogation request 210 into a signal format, such as one of pulse-interval encoding (PIE), FM0, or Miller encoding formats, modulates the encoded signal, and outputs the modulated encoded interrogation signal to RF front-end 204.
RF front-end 204 may include one or more antenna matching elements, amplifiers, filters, an echo-cancellation unit, a down-converter, and/or an up-converter. RF front-end 204 receives a modulated encoded interrogation signal from modulator/encoder 208, up-converts (if necessary) the interrogation signal, and transmits the interrogation signal to antenna 202 to be radiated. Furthermore, RF front-end 204 receives a tag response signal through antenna 202 and down-converts (if necessary) the response signal to a frequency range amenable to further signal processing.
Demodulator/decoder 206 is coupled to an output of RF front-end 204, receiving a modulated tag response signal from RF front-end 204. In an EPC Gen 2 protocol environment, for example, the received modulated tag response signal may have been modulated according to amplitude shift keying (ASK) or phase shift keying (PSK) modulation techniques. Demodulator/decoder 206 demodulates the tag response signal. For example, the tag response signal may include backscattered data formatted according to FM0 or Miller encoding formats in an EPC Gen 2 embodiment. Demodulator/decoder 206 outputs decoded data signal 214.
The configuration of transceiver 220 shown in
The present invention is applicable to any type of RFID tag.
IC 306 controls operation of tag 102, and transmits signals to, and receives signals from RFID readers using antenna 304. In the example of
Memory 308 is typically a non-volatile memory, but can alternatively be a volatile memory, such as a DRAM. Memory 308 stores data, including an identification number 318. Identification number 318 typically is a unique identifier (at least in a local environment) for tag 102. For instance, when tag 102 is interrogated by a reader (e.g., receives interrogation signal 110 shown in
Demodulator 314 is coupled to antenna 304 by antenna signal 328. Demodulator 314 demodulates a radio frequency communication signal (e.g., interrogation signal 110) on antenna signal 328 received from a reader by antenna 304. Control logic 310 receives demodulated data of the radio frequency communication signal from demodulator 314 on input signal 322. Control logic 310 controls the operation of RFID tag 102, based on internal logic, the information received from demodulator 314, and the contents of memory 308. For example, control logic 310 accesses memory 308 via a bus 320 to determine whether tag 102 is to transmit a logical “1” or a logical “0” (of identification number 318) in response to a reader interrogation. Control logic 310 outputs data to be transmitted to a reader (e.g., response signal 112) onto an output signal 324. Control logic 310 may include software, firmware, and/or hardware, or any combination thereof. For example, control logic 310 may include digital circuitry, such as logic gates, and may be configured as a state machine in an embodiment.
Modulator 316 is coupled to antenna 304 by antenna signal 328, and receives output signal 324 from control logic 310. Modulator 316 modulates data of output signal 324 (e.g., one or more bits of identification number 318) onto a radio frequency signal (e.g., a carrier signal transmitted by reader 104) received via antenna 304. The modulated radio frequency signal is response signal 112, which is received by reader 104. In an embodiment, modulator 316 includes a switch, such as a single pole, single throw (SPST) switch. The switch changes the return loss of antenna 304. The return loss may be changed in any of a variety of ways. For example, the RF voltage at antenna 304 when the switch is in an “on” state may be set lower than the RF voltage at antenna 304 when the switch is in an “off” state by a predetermined percentage (e.g., 30 percent). This may be accomplished by any of a variety of methods known to persons skilled in the relevant art(s).
Charge pump 312 (or other type of power generation module) is coupled to antenna 304 by antenna signal 328. Charge pump 312 receives a radio frequency communication signal (e.g., a carrier signal transmitted by reader 104) from antenna 304, and generates a direct current (DC) voltage level that is output on tag power signal 326. Tag power signal 326 is used to power circuits of IC die 306, including control logic 320.
Charge pump 312 rectifies the radio frequency communication signal of antenna signal 328 to create a voltage level. Furthermore, charge pump 312 increases the created voltage level to a level sufficient to power circuits of IC die 306. Charge pump 312 may also include a regulator to stabilize the voltage of tag power signal 326. Charge pump 312 may be configured in any suitable way known to persons skilled in the relevant art(s). For description of an example charge pump applicable to tag 102, refer to U.S. Pat. No. 6,734,797, titled “Identification Tag Utilizing Charge Pumps for Voltage Supply Generation and Data Recovery,” which is incorporated by reference herein in its entirety. Alternative circuits for generating power in a tag, as would be known to persons skilled in the relevant art(s), may be present. Further description of charge pump 312 is provided below.
It will be recognized by persons skilled in the relevant art(s) that tag 102 may include any number of modulators, demodulators, charge pumps, and antennas. Tag 102 may additionally include further elements, including an impedance matching network and/or other circuitry. Furthermore, although tag 102 is shown in
As further described below, according to embodiments of the present invention, a tag is enabled to respond to reader communications based on a strength of a signal received from a reader. Embodiments of the present invention are described in further detail below. Such embodiments may be implemented in the environments, readers, and tags described above, and/or in alternative environments and alternative RFID devices.
Embodiments are described herein for using tags to monitor reader transmitted signals. These embodiments can be implemented anywhere that readers and tags are used. For example, embodiments can be implemented in a commercial or industrial environment, such as in a warehouse, a factory, a business, or store, and in a military or other non-commercial environment.
Reader 430 may be configured similarly to any type of RFID reader, including the embodiments of reader 104 shown in
Signal strength request module 402 is configured to communicate (e.g., using the receiver/transmitter functionality of reader 104, such as described above) with a tag, such as tag 420, to request that the tag provide an indication to reader 430 of a strength of a signal transmitted by reader 430. Signal strength request module 402 may include any hardware, software, firmware, or any combination thereof, needed to perform its functions.
Flowchart 500 begins with step 502. In step 502, a command to measure a signal strength of a reader communication signal is transmitted to a tag. For example, the command is signal strength request command 404 shown in
In an embodiment, signal strength request command 404 may include one or more parameters. For example, verify command 404 may include a timing parameter. The timing parameter may be used in the targeted tag to dictate a time (e.g., measured from receipt of command 404) at which the tag should perform a measurement of signal strength. Alternatively, signal strength request command 404 does not include a parameter, and merely instructs one or more tags to respond with a signal strength indication.
Signal strength request command 404 is transmitted in signal strength request signal 406, shown in
In step 504, the reader communication signal is transmitted. For example, the reader communication signal is reader communication signal 414 shown in
In step 506, an indication of the strength of the transmitted radio frequency communication signal is received from the tag. For example, the received signal is signal strength response signal 416, which is received from tag 420 in
As shown in
In an embodiment, such as shown in
Flowchart 508 begins with step 510. In step 510, a command to measure a signal strength of a reader communication signal is received. For example, antenna 304 of tag 420 receives signal strength request command 404 from reader 430 in signal strength request signal 406. For example, demodulator 314 and control logic 310 may be used to recover signal strength request command 404 from signal strength request signal 406. Tag 420 may communicate according to any communications protocol mentioned herein or otherwise known.
In step 512, a strength of a received radio frequency communication signal is measured. For example, in an embodiment, receipt of signal strength request command 404 causes signal strength monitor module 410 to measure a strength of a received radio frequency communication signal (e.g., signal strength request signal 406 or reader communication signal 414). As described above, in an embodiment, signal strength request command 404 may be continuously measuring strengths of received reader signals. Thus, step 512 may occur before, during, or after step 510, depending on the particular implementation. In an embodiment, a measured signal strength may be stored in memory 308.
Furthermore, when signal strength request command 404 includes a timing parameter, signal strength monitor module 410 may include a timing module to process the timing parameter, to determine a time when a signal strength measurement should be executed. Signal strength monitor module 410 may include further modules, as needed, to process further parameters of a signal strength request command 404.
Signal strength monitor module 410 can be configured to measure signal strengths in a variety of ways, several examples of which are illustrated in detail further below.
In step 514 of
For further description regarding example signal strength monitor modules, refer to pending U.S. application Ser. No. 11/394,164, filed Mar. 31, 2006, titled “RFID Tag Receive Signal Strength Indicator,” which is incorporated herein by reference in its entirety.
Example embodiments that enable tags to response to reader communication signals based on signal strength are described as follows. These examples are provided for illustrative purposes, and are not limiting. The examples described herein may be adapted to any type of tag. Further structural and operational embodiments, including modifications/alterations, will become apparent to persons skilled in the relevant art(s) from the teachings herein.
In the embodiment of
Response enable module 610 is configured to enable a response to the read signal received from the reader, based on the signal strength measured by signal strength monitor module 608. Response enable module 610 receives signal strength indication 618 from signal strength monitor module 608. Response enable module 610 generates a response enable signal 620 indicating whether tag 600 can respond to the read signal. In an embodiment, response enable signal 610 has a first state (e.g., a “1”) to indicated that a response to the read signal is enabled, and a second state (e.g., a “0”) to indicate that a response to the read signal is not enabled (is inhibited). In other embodiments, response enable signal 610 can have more than two states (e.g., can be a multi-bit value in a digital embodiment) when a response is enabled, such that more than one response is possible (depending on the particular level of signal strength indication 618 within an acceptable, enabling range). Depending on the particular configuration of control logic 604, response enable signal 610 can be an analog or digital signal.
Control logic 604 receives response enable signal 610. If response enable signal 610 indicates that a response is enabled, control logic 604 determines data to use to respond to the read signal (or other reader signal). For instance, control logic 604 may retrieve response data from memory 606 (e.g., an identification number, sensor data, etc.). Control logic 604 provides the output data to modulator 600 on output signal 622 if response enable signal 610 indicates a response is enabled. Modulator 600 modulates the output data into a tag response that is transmitted by an antenna of tag 600.
Timer 614 is optionally present. Timer 614 is configured to measure a duration of time over which a signal strength measured by signal strength monitor module 614 is at a desired level. Response enable module 610 is configured to enable a response to the read signal if the measured duration of time is greater than a predetermined threshold time value. Response enable module 610 communicates with timer 614 over timer signal 624. For example, response enable module 610 may send timer start and timer end signals over timer signal 624 to timer 614. Timer 614 may provide response enable module 610 with a periodic time signal, an indication of an elapsed time, or other time-related signal over timer signal 624. Timer 614 may include a counter, monostable multivibrator circuit, and/or other logic to track time.
Flowchart 700 begins with step 702. In step 702, a strength of a signal from a reader is measured. For example, as described above, signal strength monitor module 608 measures a strength of a signal received from a reader, such as a RF signal transmitted by the reader to provide power to tags (e.g., a carrier wave/frequency).
In step 704, a RFID read signal is received from the reader. For example, a read signal, such as interrogation signal 110a transmitted by reader 104a, shown in
In step 706, a response to the read signal is enabled based on the measured strength. For example, as described above, response enable module 610 determines whether a response to the read signal should be enabled, based on a strength of the signal measured by signal strength monitor module 608.
For example, in an embodiment, a response to the read signal is enabled if the measured signal strength is greater than a threshold signal strength value. In such an embodiment, response enable module 610 may compare the measured signal strength received on signal strength indication 618 to a stored threshold signal strength value.
In another embodiment, a response to the read signal is enabled if the measured signal strength is less than a threshold signal strength value. In such an embodiment, response enable module 610 may compare the measured signal strength received on signal strength indication 618 to first threshold signal strength value 808. If the measured signal strength is less than first threshold signal strength value 808, a response is enabled. If the measured signal strength is greater than first threshold signal strength value 808, a response is not enabled. For example, comparator 902 of
In another embodiment, a response to the read signal is enabled if the measured signal strength is within a particular range. In such an embodiment, response enable module 610 may compare the measured signal strength received on signal strength indication 618 to a pair of threshold signal strength values. For example, as shown in
A combine logic 1006 receives and combines first and second enable signals 1008 and 1010 to determine whether signal strength indication 618 has a value between first and second threshold signal strength values 808 and 810. In the current example, if signal strength indication 618 is greater than first threshold signal strength value 808, and less than second threshold signal strength value 810, combine logic 1006 generates response enable signal 620 to provide an indication that a response to the read signal is enabled (e.g., response enable signal 620 is a “1” logical value). If signal strength indication 618 is less than first threshold signal strength value 808, or greater than second threshold signal strength value 810, combine logic 1006 generates response enable signal 620 to provide an indication that a response to the read signal is not enabled (e.g., response enable signal 620 is a “0” logical value).
For example, if as described above, first and second enable signals 1008 and 1010 are each “1” logical values when signal strength indication 618 is respectively greater than and less than the first and second threshold signal strength values 808 and 810, combine logic 1006 may include an “AND” logic gate to generate response enable signal 620 as a “1” logic value for this condition (within the range), and as a “0” logic value for other conditions (outside of range).
In step 710, a response to the read signal that includes the data object is transmitted. For instance, modulator 612 receives the selected stored data object from control logic 604 (or directly from memory 606). Modulator 612 transmits the stored data object from an antenna of tag 600 (not shown in
Note that in an embodiment, response enable signal 620 may be used by control logic 604 to select a stored data object from a plurality of stored data objects. In other words, in an enabled condition, response data may be selected from a plurality of data objects, based on a value of response enable signal 620. Thus, in an embodiment, response enable signal 620 may have more than two logical values (e.g., “0” and “1”).
For example, response enable module 610 may have one or more additional comparators than as shown in
Note that in an alternative embodiment, when response enable signal 620 indicates that tag 600 is not enabled, control logic 604 may be configured to select a stored dummy data object. The dummy data object may be transmitted from tag 600. In this manner, if a nearby reader receives the dummy data object, this may indicate to the nearby reader a variety of things. In one case, the nearby reader did not attempt to read the tag, but did receive the dummy data object from the tag. Receipt of the dummy data object may indicate to the nearby reader that another reader, including possibly an illicit reader, is attempting to interrogate a nearby tag. If the nearby reader did attempt to interrogate the tag, but received the dummy data object as a response, this may indicate to the reader that the tag is receiving weak or otherwise undesirable signal levels from the reader. Thus, the reader may need to be re-positioned for better reception by the tag.
In step 716, a response to the read signal is enabled if the measured duration of time is greater than a stored threshold time value. For example, the measured duration of time is compared by response enable module 610 to a threshold time value. For example, as shown in
Note that in embodiments, threshold values used by response enable module 610, such as first and second threshold signal strength values 808 and 810, and threshold time value 812, when present, may be hard coded into memory 606. Alternatively, these values may be programmed into memory 606 at a time of manufacture of tag 600, and/or at a later time. For example, memory 606 may be one-time programmable with these values, or these values may be updated at subsequent times, such as by reader communications with tag 600, to account for different readers, different communication environments, etc.
In this document, the terms “computer program medium” and “computer usable medium” are used to generally refer to media such as a removable storage unit, a hard disk installed in hard disk drive, and signals (i.e., electronic, electromagnetic, optical, or other types of signals capable of being received by a communications interface). These computer program products are means for providing software to a computer system. The invention, in an embodiment, is directed to such computer program products.
In an embodiment where aspects of the present invention are implemented using software, the software may be stored in a computer program product and loaded into a computer system (e.g., a reader) using a removable storage drive, hard drive, or communications interface. The control logic (software), when executed by a processor, causes the processor to perform the functions of the invention as described herein.
According to an example embodiment, a reader may execute computer-readable instructions to command a tag to provide a signal strength indication. Furthermore, in an embodiment, a tag may execute computer-readable instructions to monitor a signal strength of a reader transmitted signal and to determine whether a response to a reader communication signal is enabled based on measured signal strength, as further described elsewhere herein.
While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
The following application of common assignee is related to the present application, and is incorporated by reference herein in its entirety: “RFID Tag Receive Signal Strength Indicator,” Atty. Dkt. No. 2319.0600000, U.S. application Ser. No. 11/394,164, filed Mar. 31, 2006, now pending.
