Patent Description:
Radio Frequency Identification (RFID) tags typically include an antenna that is coupled to an RFID chip. RFID tags typically receive power from nearby radio frequency sources, such as an RFID reader or RFID printer that is transmitting radio frequency energy at the resonant frequency of the RFID tag. When interrogated by an RFID reader, the RFID tag receives power from the RFID reader and transmits a coded return signal. The RFID reader can also program the RFID tag in a similar fashion.

Some RFID printers can print multiple RFID tags from a supply roll of blank tags. Each RFID tag is generally configured individually at the time the tag is printed. To prevent multiple blanks tags on the supply roll from being accidentally configured when one of the tags is being printed, the RFID write power levels are generally kept low and the supply roll is electrically isolated from the RF antenna of the RFID printer. However, with low power levels it is possible that some RFID tags may not be programmed consistently during printing. Also, different types of RFID tags may have different sensitivities, which can require different write power levels to have to be used for different types of supply rolls of RFID tags.

<CIT> discloses a media processing apparatus which includes a self-calibrating encoding assembly that sends read/write inquires to determine appropriate power levels for encoding encodable objects. The apparatus includes a control subsystem that tracks the power levels of the encoding assembly and the corresponding positions of media carrying the encodable objects. The controller then determines an encoding window and an encoding power level at which the encoding assembly encodes an encodable object in the encoding power window without unwanted communication to encodable objects outside of the window.

<CIT> discloses a high speed tabletop and industrial printer with integrated high speed RFID encoding and verification at the same time. The industrial printer simultaneously prints on and electronically encodes/verifies RFID labels, tags, stickers attached to a continuous web. The industrial printer comprises a lighted sensor array for indexing the printing to the RFID tags; and a cutter powered from the industrial printer for cutting the web that the RFID tags are disposed on.

<CIT> discloses a system and method of adjusting the transmission strength emitted by an integrated RFID reading device by an EIR terminal. The EIR terminal scans a signal of decodable indicia, locates the decodable indicia within the signal, decodes the decodable indicia into a decoded message, which is an identifier for said physical object. The EIR terminal then makes contact with the physical object and stores the location of this contact as a point of origin and then moves through three dimensional space and receives values from its motion sensing device presenting the location of said EIR terminal in three dimensional space relative to the point of origin. Then, the EIR terminal determines the distance of the RFID reading device from the point of origin and adjusts the power level of said RFID reading device relative to this distance.

In some aspects, examples are directed to methods, comprising setting a read power level of an Radio Frequency Identification (RFID) device to an initial power level; determining a floor read power level by iteratively interrogating an RFID label with the RFID device while decreasing the read power level until either the RFID label fails to respond to the interrogation, or the read power level reaches a minimum power level; determining a ceiling read power level by iteratively interrogating the RFID label with the RFID device while increasing the read power level until either a second RFID label responds to the interrogation, or the read power level reaches a maximum power level; and configuring the read power level of the RFID device based at least in part on the floor read power level and the ceiling read power level.

In other aspects, examples are directed to apparatuses, comprising a Radio Frequency Identification (RFID) module configured to generate an RF signal; an RF attenuator configured to attenuate the RF signal; an RF antenna configured transmit the attenuated RF signal; and a controller configured to set a read power level of the attenuated RF signal to an initial power level via the RF attenuator, determine a floor read power level by iteratively interrogating an RFID label by the RFID module with the attenuated RF signal while decreasing the read power level via the RF attenuator until either the RFID label fails to respond to the interrogation, or the read power level reaches a minimum power level, determine a ceiling read power level by iteratively interrogating the RFID label by the RFID module with the attenuated RF signal while increasing the read power level until either a second RFID label responds to the interrogation, or the read power level reaches a maximum power level, and configure the read power level of the attenuated RF signal based at least in part on the floor read power level and the ceiling read power level.

Other aspects include, but are not limited to methods for determining read power levels for RFID labels; methods for determining write power levels for RFID labels; RFID antennae and controllers configured to determine read and write power levels for RFID tags; RF shields configured to isolate the RFID antenna from a supply roll of RFID labels; RFID printers configured to determine power levels for interrogating and programming individual RFID labels from a supply roll of RFID labels.

The systems and methods disclosed herein are described in detail by way of examples and with reference to <FIG>. It will be appreciated that modifications to disclosed and described examples, arrangements, configurations, components, elements, apparatuses, devices methods, systems, etc. can suitably be made and may be desired for a specific application. In this disclosure, any identification of specific techniques, arrangements, etc. are either related to a specific example presented or are merely a general description of such a technique, arrangement, etc. Identifications of specific details or examples are not intended to be, and should not be, construed as mandatory or limiting unless specifically designated as such.

The present disclosure illustrates new modalities for determining optimal power levels for reading and writing individual RFID chips on RFID printers. The systems and methods disclosed herein describe various aspects of determining and configuring read and write power levels so that only the selected RFID tag is targeted, and other RFID tags, such as an internal supply roll of blank RFID tags are not incidentally written to or read by the RFID device.

RFID devices can operate on different frequency bands are generally designed for different functions and are typically manufactured separately. RFID devices can be used for many different purposes including, for example, item identification, item tracking, and inventory. As can be appreciated, items can include different RFID devices to provide the respective benefits of each of the RFID devices. Different types of RFID devices can have different sensitivities. Certain RFID tags can be reliably interrogated with lower power levels than other types of RFID tags. Certain RFID tags can require higher write power levels than the power level necessary to read the same RFID tags. Still other RFID tags may be able to use a wide range of suitable power levels, while other RFID tags may require power levels to be within a narrower range. Different types of RFID printers may be better than other types at shielding RFID tags that are still on an internal supply roll of blank RFID tags.

RFID printers and RFID readers may need to be configured differently for different types of RFID tags. Instead of manually configuring each RFID printer or RFID reader with each type of supply roll of RFID tags, the present disclosure presents a system and method for determining suitable read and write power levels for writing individual RFID tags without accidentally reading or writing unintended RFID tags, such as blank RFID tags carried internally on a supply roll inside a portable RFID printer.

Turning to <FIG>, a portable RFID printer <NUM> is presented. The RFID printer <NUM> includes a power source <NUM> such as a field replaceable battery or rechargeable battery pack. The RFID printer <NUM> includes a <NUM> port through which printed RFID tags emerge from the RFID printer <NUM>. The RFID printer <NUM> also includes a display screen <NUM> configured to provide print details and control options to the user. The display screen <NUM> is driven by a display controller board which can optionally include circuitry for reading and writing RFID chips. The RFID printer can include one or more other circuit boards, which can alternatively include such circuitry, such as a print control board <NUM>, and a print engine board <NUM>. Any suitable circuit boards, controllers, or electronic module assemblies can be used as would be understood in the art. An example portable RFID printer is the <NUM> Printer from the Avery Dennison Corporation (Glendale, CA). As can be appreciated however, other RFID printers can alternatively be suitable including non-portable RFID printers.

Turning now to <FIG>, an internal view <NUM> of the portable RFID printer <NUM> of <FIG> is presented. In this internal view <NUM>, an example antenna <NUM> for programming RFID labels <NUM> is illustrated. Individual RFID labels <NUM>, also called RFID tags, are printed from a supply roll <NUM> of labels. Each of the RFID labels <NUM> includes an RFID chip <NUM> and an RFID antenna <NUM> disposed on a suitable substrate, such as plastic substrate, polyethylene terephthalate (PET) substrate, paper or cardboard substrate, polyethylene substrate, etc. The RFID chip <NUM> is electrically coupled to the RFID antenna <NUM>. The example RFID label <NUM> illustrated in <FIG> uses a coil antenna for the RFID antenna <NUM>. RFID tags using coil antennas generally operate in the high frequency (HF) spectrum, for example at or near <NUM>, and are designed primarily to be driven by a near magnetic field reader such as that incorporated into handheld readers. RFID tags using monopole or dipole antennas can operate in the ultrahigh frequency (UHF) spectrum, for example at <NUM> to <NUM>, or <NUM> to <NUM>. Other types of RFID tags can be used as would be understood in the art. The RFID label <NUM> can include printing (not shown) on one of the sides. Because of the proximity of the supply roll <NUM> of labels to the antenna <NUM>, it is important to properly control read and write power levels to ensure the antenna <NUM> only reads or programs the individual RFID label <NUM> that is proximate to the antenna <NUM>. If power levels are too high, or if the supply roll <NUM> is not properly isolated from the antenna <NUM>, the antenna <NUM> can inadvertently read or program multiple RFID labels <NUM> such as those on the supply roll <NUM>.

Turning now to <FIG>, a functional diagram of a first system <NUM> for controlling read and write power levels in presented. The system <NUM> can include one or more host controllers <NUM> that provides data for programming the RFID chips. Example host controllers <NUM> can include a server, cloud based services, and so forth. A local controller <NUM> on an RFID printer, such as a portable RFID printer, communicates with the host controller <NUM>, for example when a user operating the portable RFID printer downloads the data to the RFID printer for printing a batch of RFID labels. The power source <NUM>, for example a battery power source as illustrated, provides power to the portable RFID printer. Regulators <NUM>, <NUM> provide suitable voltages required by the various components of the portable RFID printer. An RFID reader module <NUM> generates suitable RF signals for reading and writing the RFID chips on RFID labels. An RF Digital Step Attenuator <NUM>, suitably controlled by the local controller <NUM>, modifies the power level of RF signals sent to the antenna <NUM> so as to prevent the antenna <NUM> from reading or writing to RFID tags that are not immediately proximate to the antenna <NUM> as described in greater detail with regard to <FIG> and <FIG> and the accompanying detailed description. Internal isolation shielding <NUM> further isolates the RF signals so that read and write operations are only performed with RFID tags that are proximate to the antenna <NUM>. The internal isolation shielding <NUM> can also shield circuitry from RF energy from the antenna <NUM>.

Turning now to <FIG>, a functional diagram of a second system <NUM> for controlling RFID read and write power levels is presented. The system <NUM> can include one or more host controllers <NUM> that provides data for programming the RFID chips. Example host controllers <NUM> can include a server, cloud based services, and so forth. A local controller <NUM> on an RFID printer, such as a portable RFID printer, communicates with the host controller <NUM>, for example when a user operating the portable RFID printer downloads the data to the RFID printer for printing a batch of RFID labels. The power source <NUM>, for example a battery power source as illustrated, provides power to the portable RFID printer. Regulators <NUM>, <NUM> provide suitable voltages required by the various components of the portable RFID printer. An RFID reader module <NUM> generates suitable RF signals for reading and writing the RFID chips on RFID labels.

Different antennas can be configured on a portable RFID printer. For example, an internal near field antenna <NUM>, such as RFID antenna <NUM> of <FIG>, can be used to program RFID tags that are printed by the portable RFID printer. An external far field antenna <NUM> can be used by the portable RFID printer to interrogate RFID tag outside the portable RFID printer, for example RFID tags attached to merchandise. This configuration allows the portable RFID printer to also be used as an RFID scanner. In embodiments, the portable RFID printer can use the external far field antenna <NUM> to program or re-program existing RFID tags that may be attached to merchandise or otherwise are not inside the portable RFID printer. An RF Digital Step Attenuator <NUM>, suitably controlled by the local controller <NUM>, modifies the power level of RF signals sent to one or more of the antennas <NUM>, <NUM> so as to prevent the antennas <NUM>, <NUM> from reading or writing to RFID tags that are not in proximity to one of the antennas <NUM>, <NUM> as described in greater detail with regard to <FIG> and <FIG> and the accompanying detailed description. An RFID multiplexor <NUM> distributes the RF signals from the RF Digital Step Attenuator <NUM> to the antennas <NUM>, <NUM>. For example, when programming an RFID tag that is inside the portable RFID printer, the local controller <NUM> can set the RF Digital Step Attenuator <NUM> to a first power level, while when configured to scan or program an RFID tag that is external to the portable RFID printer, the local controller <NUM> can set the RF Digital Step Attenuator <NUM> to a second power level, for example a higher power level as would typically be the case. Internal isolation shielding <NUM> further isolates the RF signals so that read and write operations are only performed with RFID tags that are proximate to one or more of the antennas <NUM>, <NUM>. The internal isolation shielding <NUM> can also shield circuitry from RF energy from the antennas <NUM>, <NUM>.

Turning to <FIG> and <FIG>, a flowchart <NUM> of example operations of a system for controlling RFID read/write power levels is presented. Operation starts at start block <NUM> and continues to block <NUM> where the initial RFID test and read power levels are configured. Progress continues to block <NUM> where the read is found and the read power is set to the midpoint between the test minimum and the test maximum. Any suitable initial power level can be selected. For example, the initial RFID read power level can be configured to be the midpoint between the minimum configurable read power level and the maximum configurable read power level. The initial minimum and maximum power levels can be hard coded or retrieved from a suitable data store, such as data store. The process continues in block <NUM> where the system transmits an RFID interrogation signal via the RF antenna of the system, which can be, for example, the internal antenna of the portable RFID printer of <FIG>. The RFID interrogation signal energizes RFID tags proximate to RF antenna and, based on the read power level and proximity of nearby RFID tags, the system can receive back responses from no RFID tags, a single RFID tag, or multiple (or many) RFID tags.

If at block <NUM> no RFID tags responded to the RFID interrogation at block <NUM>, then progress is made to block <NUM> to determine if the read power can be increased by setting the test minimum to read power plus <NUM>. At block <NUM>, if the read power is already at the maximum level, then the process terminates at block <NUM>, otherwise the read power level is incremented by <NUM> at block <NUM> and the process continues back to block <NUM> to perform the RFID interrogation at the increased read power level. The read power level can be incremented at any suitable interval, for example by one dB or by one step available by the RF Digital Step Attenuator of <FIG>.

If at block <NUM> one or more RFID tags responded to the RFID interrogation, then progress proceeds to block <NUM>. At block <NUM>, if multiple RFID tags responded to the RFID interrogation, then progress is made to block <NUM> to determine if the read power can be decreased. The read power is decreased by one at block <NUM> and the process continues back to blocks <NUM> and <NUM> to perform the RFID interrogation at the decreased read power level.

If at block <NUM> exactly one RFID tag responded, then progress proceeds to block <NUM> to set the good read power to the read power and to set the test maximum to read power minus <NUM>. At block <NUM> the read power level is decreased. The read power level can be decreased at any suitable interval, for example by one dB or by one step available by the RF Digital Step Attenuator of <FIG>. At block <NUM>, the floor read level is determined by checking where one RFID tag will still respond to the RFID interrogation. At block <NUM> the read power level is set to the midpoint between the test level minimum and test level maximum.

At block <NUM>, the RFID interrogation is performed at the reduced read power level. If at block <NUM> multiple RFID tag continues to respond, then progress is made back to block <NUM> to decrease the read power level and perform another RFID interrogation at blocks <NUM> and <NUM>. Once the RFID tag stops responding to the RFID interrogation at block <NUM>, or if the minimum read level is reached, then at block <NUM> progress is made to block <NUM> where the power is increased to the level where the RFID tag last responded to the RFID interrogation and that power level is stored as the floor read level, for example by setting the test level minimum to the read power plus <NUM>. At block <NUM>, if the test level minimum is greater than or equal to the test level maximum, the process returns to block <NUM>. If not, then the process moves to block <NUM> where the read level floor is set to the test level maximum plus <NUM>, the test level minimum is set to the good read level power plus <NUM> and the test level maximum is set to the maximum power level. In embodiments, the floor read level can be set at any suitable level where the one RFID tag continues to respond, for example by increasing the read level by two or three dB, or by two or three steps via an associated RF Digital Step Attenuator.

Progress continues to block <NUM> where the ceiling read level at which the one RFID tag will still respond to the RFID interrogation, but no additional RFID tags will also respond. If at block <NUM> the test minimum is greater than or equal to the test maximum, then the process returns to block <NUM>. If not, the process moves onto block <NUM>. At block <NUM> the read power level is increased. At block <NUM>, the read floor level is set to the test level maximum plus <NUM>, the test level minimum is set to the good read power level plus <NUM> and the test level maximum is set to the maximum power level. The read power level can be increased at any suitable interval, for example by one dB or by one step available by the RF Digital Step Attenuator of <FIG>.

The ceiling level is determined in block <NUM> and then in block <NUM> the read power level is set to the midpoint between test level minimum and the test level maximum. Progress continues to block <NUM> where the RFID read power level for the system is configured. Any suitable RFID read power level can be selected. For example, the RFID read power level can be configured to be the midpoint between the ceiling read power level and the floor read power level. The RFID read power level can be stored in a suitable data store, such as data store. At block <NUM>, the RFID interrogation is performed at the increased read power level. If at block <NUM> only one RFID tag continues to respond, then progress is made to block <NUM> to determine if the read power level is greater than the read ceiling level. If so, at block <NUM> the read ceiling level is set to the read power level and then at block <NUM> the test level minimum is set to the read power level plus <NUM>. If not, the process moves to block <NUM> where the test minimum is increased, for example, by setting to the read power plus <NUM>. At block <NUM>, if the test level minimum is not greater than or equal to the test level maximum then the process moves back to block <NUM> and if so then the process moves onto block <NUM>, where the read power is set to the midpoint of the floor read level and ceiling read level and set the write power level to the read power level.

At <NUM>, if no tags are detected, the test level minimum is set to the read power plus <NUM> in block <NUM> before moving onto block <NUM>, where the read power is set to the midpoint of the floor read level and ceiling read level and set the write power level to the read power level.

Once multiple RFID tags begin to respond to the RFID interrogation at block <NUM>, or if the maximum read level is reached, the maximum power is set to the read power at block <NUM>. If the test minimum is not greater than or equal to the maximum power at block <NUM>, then progress is made to block <NUM> where the power is decreased (for example, by setting the test maximum to the read power minus <NUM>) to the level where only one RFID tag responded to the previous RFID interrogation and that power level is stored as the ceiling read level. If the test minimum is greater than or equal to the maximum power at block <NUM>, then the process moves to block <NUM> where the read power is set to the midpoint of the floor read level and ceiling read level and set the write power level to the read power level. In embodiments, the ceiling read level can be set at any suitable level where the one RFID tag continues to respond but other RFID tags do not also respond, for example by decreasing the read level by two or three dB, or by two or three steps via an associated RF Digital Step Attenuator.

If the write power level is less than the maximum power level minus <NUM> at block <NUM>, then progress continues to block <NUM> to configure the RFID write power level. If not, then the process terminates at block <NUM>. If the RFID tag write operation at blocks <NUM> and <NUM> is not successful, then the write power is incremented at block <NUM>. If the write power is less than the maximum power minus <NUM>, then the process continues back to block <NUM> to perform the RFID write operation at the RFID write power level. If the RFID tag write operation at blocks <NUM> and <NUM> is successful, then at block <NUM> the write power is increased by <NUM>, for example. The process progresses to block <NUM> to determine if the write power is greater than the maximum level. If so, the process terminates at block <NUM>. If not, then at block <NUM> the RFID read power level and/or write power level can be stored in a suitable data store. The process then terminates at block <NUM>.

Example pseudocode for determining optimal read and write power levels is presented below:
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Referring now to <FIG>, a section view of an example portable RFID printer <NUM> is presented. The portable RFID printer <NUM> includes an RFID antenna board <NUM>, a supply roll <NUM> of RFID tags, a print head retainer <NUM>, an RF shield <NUM>, and a transfer roller <NUM> among other parts. A dotted arrow line illustrates the path <NUM> of the RFID tags through the portable RFID printer <NUM>.

The RFID antenna board <NUM> acts as an upper supply guide to direct the RFID labels from the supply roll <NUM> along the path <NUM> into the print nip <NUM>. The RFID antenna board <NUM> includes an integral RFID antenna that is used to program the RFID tags as they travel along the path <NUM> from the supply roll <NUM> to underneath the RFID antenna board <NUM> and into the print nip <NUM>.

Due to space restrictions in the portable RFID printer <NUM>, the supply roll <NUM> of RFID labels is in close proximity to the RFID antenna board <NUM>. The RF shield <NUM> provides RF shielding to isolates RFID labels on the supply roll <NUM> so that read and write RFID operations are only performed with RFID labels that are underneath and proximate to the RFID antenna board <NUM>. Along with adjusting the strength of the RFID signals described above, the RF shield <NUM> helps to ensure that the RFID antenna board <NUM> does not erroneously couple RF signals to the adjacent RFID labels on the supply roll <NUM>. The RF shield <NUM> can include a bent but continuous wall that extends across the entire width of the supply roll <NUM>, from the RFID antenna board <NUM> at the bottom to the top of the cavity for the supply roll <NUM>.

Referring also to <FIG>, selected components <NUM> of a portable RFID printer are illustrated including an RFID antenna board <NUM> and an associated RF cable <NUM>, a print head retainer <NUM>, an RF shield <NUM> and an associated grounding cable <NUM>, and a transfer roller <NUM>. The components <NUM> includes features configured to facilitate assembly and alignment while also reducing the likelihood of jamming. For example, a notch <NUM> in the RFID antenna board <NUM> mates with a locating rib <NUM> in the print head retainer <NUM>. A wing <NUM> on each side of the RFID antenna board <NUM> mates with a retaining pocket <NUM> of the print head retainer <NUM>. Retaining clips <NUM> secure the RF shield <NUM> to the print head retainer <NUM>.

Referring also to <FIG> presents a first diagram <NUM> of RFID labels <NUM> from a substantially new supply roll <NUM> of RFID tags, while <FIG> presents a second diagram of RFID tags <NUM> from a nearly empty supply roll <NUM> of RFID tags. In <FIG>, the RFID labels <NUM> include a slight scalloping effect <NUM>, while in <FIG>, the RFID labels <NUM> include a substantial scalloping effect <NUM>. The scalloping effect <NUM>, <NUM> occurs because the supply roll <NUM>, <NUM> is constructed with internally laminated plastic inlays. The carrier web of RFID labels <NUM>, <NUM> tends to scallop as the RFID labels <NUM>, <NUM> unspool off the supply rolls <NUM>, <NUM>. This is due to the memory of curvature that has been induced into the individual butt-cut or die-cut RFID labels <NUM>, <NUM> while they are wrapped around the core of the supply rolls <NUM>, <NUM>. The scalloping effect <NUM>, <NUM> can cause the leading edge of one or more of the RFID labels <NUM>, <NUM> to snag on any feature within the supply path and delaminate from the carrier web, causing jamming.

Referring back to <FIG>, because the RFID antenna board <NUM> functions as an upper supply guide that spans the width of the RFID labels. The RFID antenna board <NUM> directs the RFID labels into the print nip. Any mechanical means of attaching the RFID antenna board <NUM> to the print head retainer <NUM>, such as countersunk screws, rivets, and so forth would present a protrusion or edge within the supply path that can result in the leading edge of an RFID label snagging, delaminating, and causing a jam. To eliminate protrusions and edges, each side of the RFID antenna board <NUM> includes a wing <NUM> that extends outside of the supply path. The wings <NUM> mate with a corresponding retaining pocket <NUM> of the print head retainer <NUM>. Similarly, the notch <NUM> in the RFID antenna board <NUM> that mates with the locating rib <NUM> in the print head retainer <NUM> in an area that is displaced away from the supply path to eliminate the possibility of snagging and jamming.

Claim 1:
A method, comprising:
a Radio Frequency Identification, RFID, device (<NUM>) setting a read power level of the device to an initial power level;
the RFID device determining a floor read power level by iteratively interrogating a selected RFID label (<NUM>), proximate the RFID device while decreasing the read power level until either
the selected RFID label fails to respond to the interrogation, or
the read power level reaches a minimum power level;
the RFID device determining a ceiling read power level by iteratively interrogating the selected RFID label while increasing the read power level until either
another RFID label, different from the selected RFID label, responds to the interrogation, or
the read power level reaches a maximum power level; and
configuring the read power level of the RFID device based at least in part on the floor read power level and the ceiling read power level.