Patent Description:
Although other RFID technologies can be used, the disclosure focuses on high frequency ("HF"), operating at <NUM> and ultra-high frequency ("UHF") technology, operating at various bands worldwide including <NUM>-<NUM> in Europe and <NUM>-<NUM> in the United States. Accordingly, the present specification makes specific reference thereto. However, it is to be appreciated that aspects of the present inventive subject matter are also equally amenable to other like applications.

Generally stated, radio-frequency identification is the use of electromagnetic energy to stimulate a responsive device (known as an RFID "tag" or transponder) to identify itself and, in some cases, provide additionally stored data in the tag. RFID tags typically include a semiconductor device commonly called the "chip" on which are formed a memory and operating circuitry, which is connected to an antenna. Typically, RFID tags act as transponders, providing information stored in the chip memory in response to a radio frequency ("RF") interrogation signal received from a reader, also referred to as an interrogator. In the case of passive RFID devices, the energy of the interrogation signal also provides the necessary energy to operate the RFID tag device.

RFID tags may be incorporated into or attached to articles to be tracked. In some cases, the tag may be attached to the outside of an article with adhesive, tape, or other means and in other cases, the tag may be inserted within the article, such as being included in the packaging, located within the container of the article, or sewn into a garment. The RFID tags are manufactured with a unique identification number which is typically a simple serial number of a few bytes with a check digit attached. This identification number is incorporated into the tag during manufacture. The user cannot alter this serial/identification number and manufacturers guarantee that each serial number is used only once. Such read-only RFID tags typically are permanently attached to an article to be tracked and, once attached, the serial number of the tag is associated with its host article in a computer data base.

Currently, RFID technology implemented in food items to be cooked in a microwave oven cannot survive the high-field emissions of a microwave oven. More specifically, the RFID tag is typically destroyed in the microwave oven cavity and may also damage the food item to which the RFID tag is attached. Therefore, microwave safe RFID tag devices that can function within a microwave oven and that do not damage the food item to which the RFID tag is attached are needed. <CIT> relates to an RFID device including a conductive loop shield for a loop antenna. <CIT> describes RFID tags that include capacitive shields to capacitively couple with antennas of the RFID tags when exposed to threshold levels of electromagnetic energy, such as when placed in a microwave. <CIT> relates to an assembly for a RF communication circuit including an electrically insulating substrate having a first side and a second side.

The present invention discloses a microwave safe RFID tag that is secured to a food item or other product to be cooked, heated, reheated and/or thawed in a microwave oven, and that does not need to be removed from the food item or product before initiating the microwave process. Further, the RFID tag can be placed inside a microwave oven without damaging the food item or product to which the RFID tag is attached and provides data for controlling the cooking process.

The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosed innovation. This summary is not an extensive overview, and it is not intended to identify key/critical elements or to delineate the scope thereof. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

The subject matter disclosed and claimed herein, in one aspect thereof, comprises a microwave safe RFID tag device that is secured to a food item or other product to be cooked, heated, reheated and/or thawed in a microwave oven. The RFID tag may include a wide variety of information including, without limitation, information about the product to which it is attached, the user of the RFID tag, instructions for the operation of the microwave oven, etc..

In accordance with an embodiment of the present invention there is provided a radio-frequency identification, RFID, tag tolerant of microwave emissions at <NUM> comprising a RFID chip; an antenna conductor; a split ring conductor; and a dielectric positioned between the antenna conductor and the split ring conductor, wherein the antenna conductor comprises a gap and the RFID chip is positioned in the gap, and wherein a path connects the split ring conductor formed on one side of the dielectric and the antenna conductor formed on an opposite side of the dielectric, so that the split ring conductor acts as a HF bridge between a center and an edge of the antenna conductor.

In another embodiment, there is provided a radio-frequency identification, RFID, tag for use in a microwave oven tolerant of microwave emissions at <NUM> and comprising RFID chip; a coil antenna conductor; a first split ring conductor; and a second split ring conductor, wherein the coil antenna conductor comprises a gap and the RFID chip is positioned in the gap, wherein the first split ring conductor comprises a first gap and the second split ring conductor comprises a second gap, and wherein the second split ring conductor is rotated opposite of the first split ring conductor such that the first gap does not align with the second gap.

In a further embodiment of the present invention, there is provided a radio-frequency identification, RFID tag for use in a microwave field tolerant of microwave emissions at <NUM> and comprises a RFID chip secured to a strap, the strap incorporating a top shield metalization to create a shielded strap; a coil antenna conductor; and a split ring conductor comprising a gap formed therein, wherein the RFID chip and the shielded strap are positioned on the coil antenna conductor and wherein the split ring conductor is positioned on top of the RFID chip and the shielded strap, and wherein the shielded strap acts as a continuous conductor over the coil antenna conductor, and wherein the split ring conductor is placed on top of the coil antenna conductor with the gap shorted across by the shielded strap and capacitive coupling.

While the discussion contained herein primarily references food items placed into a microwave oven for purposes of cooking, thawing, heating or reheating said food item, it should be appreciated that the present invention is not limited to use with food items. More specifically, the present invention has application in any other setting or process in which it is desirable to attach an RFID tag to an article to be placed in or near a microwave oven or field, such as in a manufacturing process.

To the accomplishment of the foregoing and related ends, certain illustrative aspects of the disclosed innovation are described herein in connection with the following description and the annexed drawings. These aspects are indicative, however, of but a few of the various ways in which the principles disclosed herein can be employed and is intended to include all such aspects. Other advantages and novel features will become apparent from the following detailed description when considered in conjunction with the drawings.

The present invention discloses a RFID tag that is tolerant to high-field emissions and may be considered microwave safe such that the tag does not need to be removed from a product, such as a food item, before cooking, thawing, heating and/or reheating in an apparatus such as in a microwave, and that can provide data to control the cooking process. The RFID tag, in one embodiment, comprises a split ring (or shield) conductor formed on one side of a substrate (or dielectric), a coil antenna conductor formed on an opposite side of the substrate, and a RFID chip. The split ring conductor capacitively couples to the coil antenna conductor via the dielectric and a gap in the split ring conductor prevents arcing. Further, the RFID chip may carry data related to the product or food item to which the RFID is attached and/or the process that the microwave oven is required to perform. The data on the RFID chip is read by an RFID reader system to authorize and/or control the microwave process, for example, to cook, heat, reheat or thaw a food item.

Referring initially to the drawings, <FIG> illustrates a standard high frequency (HF) RFID tag device <NUM>. The HF RFID tag device <NUM>, in one embodiment, is a planar structure of conductive antenna components <NUM> in a spiral type configuration, or any other suitable configuration as is known in the art. Further, the planar structure is shown as a rectangle, but can be any suitable shape as is known in the art, such as a circle, square, or triangle, etc. The planar structure with the spiral type configuration creates plurality of gaps <NUM> between the conductive antenna components <NUM>. Additionally, a gap <NUM> in the conductive antenna component <NUM> itself is where a RFID chip <NUM> is positioned, such that the RFID chip <NUM> is placed into the coil of the conductive antenna component <NUM>. Further, the center <NUM> of the HF RFID tag device <NUM> and the outer edge <NUM> of the planar structure of conductive antenna components <NUM> are bridged together with a conductive trace <NUM> creating an inductor (or bridge conductor) <NUM> across the HF RFID tag device <NUM> and resonating at the wanted frequency.

Typically, HF RFID tags operate in the band of <NUM> to <NUM>, with a particular standard frequency of <NUM>. Further, typical read ranges are up to approximately <NUM>; however, for a number of applications with mobile devices such as a cell phone operating according to the Near Field Communications (NFC) standard, ranges can only be <NUM>-<NUM> depending on RFID tag size. The distance between tag and reader is in the near field, and the coupling is primarily magnetic, and a coil type antenna of an inductance designed to resonate with the RFID chip capacitance is typically used.

As shown in <FIG>, RFID tag <NUM> that is high-emission field tolerant and generally recognized as microwave safe is shown which is designed to be placed inside a heating apparatus without damaging the food item or other product the RFID tag <NUM> is attached to. The RFID tag <NUM> can be secured by any suitable means as is known in the art to the food item such as by a GRAS (Generally Recognized As Safe) adhesive. Further, the RFID tag <NUM> can be a dual mode tag or a single mode tag and may comprise a HF core component which communicates with a HF reader system, as described in <FIG>. Typically, the RFID tag <NUM> can be any suitable size, shape, and configuration as is known in the art without affecting the overall concept of the invention. One of ordinary skill in the art will appreciate that the shape and size of the RFID tag <NUM> as shown in <FIG> is for illustrative purposes only and many other shapes and sizes of the RFID tag <NUM> are well within the scope of the present disclosure. Although dimensions of the RFID tag <NUM> (i.e., length, width, and height) are important design parameters for good performance, the RFID tag <NUM> may be any shape or size that ensures optimal performance during use.

The RFID tag device <NUM> capable of withstanding a microwave oven comprises, in one embodiment, a planar structure of conductive antenna components <NUM> in a spiral type configuration, or any other suitable configuration as is known in the art. The present invention contemplates that the conductive antenna components <NUM> are metallic, but can be manufactured of any suitable material as is known in the art. Further, the planar structure is shown as a rectangle, but can be any suitable shape as is known in the art, such as a circle, square, or triangle, etc. The planar structure with the spiral type configuration creates gaps <NUM> between the conductive antenna components <NUM>. Additionally, at least one gap <NUM> in the conductive antenna component <NUM> itself is where a RFID chip <NUM> is positioned, such that the RFID chip <NUM> is placed into a coil of the conductive antenna component <NUM>.

Further, the center <NUM> of the microwave safe RFID tag device <NUM> and the outer edge <NUM> of the planar structure of conductive antenna components <NUM> may be bridged together with a conductive trace <NUM> creating an inductor (or bridge conductor) <NUM> across the microwave safe RFID tag device <NUM> and resonating at the wanted frequency. Furthermore, the microwave safe RFID tag device <NUM> comprises a second conductor <NUM> in the form of a split ring, or any other suitable shape as is known in the art. This second conductor (or ring conductor) <NUM> is separated from the bridge conductor (or coil conductor) <NUM> by a dielectric <NUM>. This dielectric <NUM> is typically a plastic or an adhesive, or any other suitable dielectric material as is known in the art.

Preferably, the ring conductor <NUM> covers the majority of the conductive antenna components or coil <NUM> as shown in <FIG>, leaving a small gap <NUM> or open space that does not cover the coil <NUM>. The shape and size of the split ring conductor <NUM> is designed as part of the overall microwave safe RFID tag device's <NUM> structure to provide a controlled interaction with the microwave field to minimize heating and prevent arcing. Typically, the design of the split ring conductor <NUM> varies, and any suitable shaped conductor as is known in the art can be used. Further, common features of the split ring conductor <NUM> would be rounded corners, defined lengths of sides compared to a wavelength at the microwave frequency, and controlled gaps between ring elements, i.e., coils <NUM>.

The split ring conductor <NUM> capacitively couples to the coil <NUM> via the dielectric <NUM>. For example, for a <NUM> square area and a <NUM> thick dielectric of k=<NUM>, the capacitance is ~106pF (picofarads). At <NUM>, the equivalent coupling impedance to the coil <NUM> is <NUM> ohms, which will have minimal impact on the coil operation. At <NUM>, the coupling impedance is ~<NUM> ohms, effectively shorting the coil and ring. This prevents arcs between the coil elements and excessive currents flowing over the full length in the coil conductors <NUM>. Thus, prevention of the arc reduces energy applied to the microwave safe RFID tag <NUM>, and heating of the microwave safe RFID tag <NUM> is then minimized as well. Accordingly, the microwave safe RFID tag <NUM> can be read before or during the high-power microwave emission, i.e., <NUM>.

The ring conductor <NUM> is split (or gap) <NUM> to prevent it acting as a shorted turn, where it magnetically interacts with the coil antenna <NUM> as current will flow in it when it is placed in a magnetic field. In the region of the split (or gap) <NUM>, the microwave current flows through the coil conductors <NUM> over a length defined by the gap <NUM> in the ring conductor <NUM> as on either side the coil conductors <NUM> are strongly coupled to the ring conductor <NUM>. The size of the gap <NUM> is chosen such that any structure of the coil <NUM> in the gap <NUM> will not interact with the microwave field; for the purposes of this invention this should be less than one tenth of a wavelength at the microwave frequency, or approximately <NUM>.

Additionally, the RFID chip <NUM> of the microwave safe RFID tag <NUM> carries data related to the process the microwave oven is required to perform. Specifically, data received from the RFID chip <NUM> may include, but is not limited to, a unique identifier for the RFID tag <NUM>, product identification, product "use by" data, product "consume by" date, allergen information, cooking parameters for the food, instructions such as heat, stir, and dwell time after heating, etc..

For example, with respect to expired product "use by" or "consume by" dates, the RFID chip <NUM> could be used to prevent the microwave from operating to thaw, cook, heat or reheat the food without a manual override, thereby preventing the user from unknowingly consuming food that is no longer fit for consumption and preventing illness. This feature is particularly useful when, for example, the printed on information containing the product "use by" or "consume by" dates is no longer readable by the human eye, or gets separated from the food product.

Additionally, the needed authorization to override the RFID chip <NUM> could be different for different food products and/or for different users. For example, the override needed for foods for infants, seafood, or foods with particular known allergens (e.g., foods that have peanuts) could be considered high risk and could require a specific password, rather than a simple yes/no or verbal confirmation. Further, this particular product data can also be combined with data about the user, such as allergen information, to preventing cooking actions, sound an alarm, ask for verbal confirmation, etc. Further, the RFID chip <NUM> can also be associated with a sensor that can detect whether the food product is thawed, chilled or frozen, and information or output from the sensor could, in turn, be used to modify the cooking parameters appropriately without further user interaction. For example, for frozen food products, the sensor output could be used to instruct the microwave oven to first thaw the food product at one microwave power setting, and then cook the food product at a different power setting. Alternatively, if the food product is determined by the sensor to already be thawed, the sensor output may be used to instruct the microwave oven to bypass the thaw process and proceed straight to the cooking process, thereby saving both time and the energy necessary to operate the microwave oven during the thaw process.

In another embodiment as shown in <FIG>, the microwave safe RFID tag device <NUM> is shown with the shield conductor <NUM> in proximity to the HF RFID coil antenna (or coil conductor) <NUM>. Further, the shield conductor <NUM> is separated from the coil conductor <NUM> via a dielectric (or substrate) <NUM>, such as a plastic or adhesive, etc., or any other suitable material as is known in the art. Additionally, the microwave safe RFID tag device <NUM> can be made in a variety of ways. For example, the shield conductor <NUM> and the coil conductor <NUM> can be positioned on opposite surfaces of a substrate (or dielectric) <NUM> such as a PET substrate <NUM> wherein the coil conductor <NUM> is etched on one side of the PET substrate <NUM> and the shield conductor <NUM> is etched on the other.

Or, the shield conductor <NUM> and the coil conductor <NUM> can be positioned on opposite surfaces of a PET substrate <NUM> where the coil conductor <NUM> is laser cut on one side of the PET substrate <NUM> and the shield conductor <NUM> is laser cut on the other side of the PET substrate <NUM>. Or, the shield conductor <NUM> and the coil conductor <NUM> can be positioned on opposite surfaces of a PET substrate <NUM> where the coil conductor <NUM> is laser cut on one side of the PET substrate <NUM> and the shield conductor <NUM> is die cut on the other side of the PET substrate <NUM>. Or, the shield conductor <NUM> and the coil conductor <NUM> can be positioned on opposite surfaces of a PET substrate <NUM> where the coil conductor <NUM> is laser cut or etched on one surface of the PET substrate <NUM> and the shield conductor <NUM> is previously cut and applied with an adhesive to the other surface of the PET substrate <NUM>.

Alternatively, the shield conductor <NUM> and the coil conductor <NUM> can be on the same surface of a PET substrate <NUM> where the coil conductor <NUM> is laser cut or etched on one surface of the PET substrate <NUM> and the shield conductor <NUM> is previously cut and applied as an additive component with an adhesive to the same surface of the PET substrate <NUM>. Or finally, the shield conductor <NUM> and the coil conductor <NUM> can be either on the same or on opposite surfaces of the PET substrate <NUM> where the shield conductor <NUM> is applied as a printed structure, either on the back of the PET substrate <NUM> or on top of the coil conductor <NUM> with a suitable dielectric separator such as a varnish in between, or any other suitable dielectric material as is known in the art.

<FIG> provides a view of the microwave safe RFID tag <NUM>, specifically the area where the gap <NUM> in the split ring (or shield) conductor <NUM> is over the HF coil antenna conductor <NUM>. The gap <NUM> discloses a large overlap area <NUM> on either side. The large overlap area <NUM> provides a low impedance coupling to the coil antenna conductor <NUM> on either side of the coil turns, as they are shorted together capacitively by the shield conductor <NUM>. Thus, the shield conductor <NUM> acts as a single wide conductor capable of carrying the current across the gap <NUM>. This prevents arcs between the coil elements (or turns) and excessive current flowing over the full length of the coil antenna conductor <NUM>. In the gap <NUM> area, the microwave current flows through the coil elements over a length defined by the gap <NUM>, as on either side the coil antenna conductor <NUM> is strongly coupled to the split ring conductor <NUM>. The size of the gap <NUM> is chosen such that any structure of the coil elements in the gap <NUM> will not interact with the microwave field, for example, the size of the gap <NUM> should be less than one tenth of a wavelength at the microwave frequency, or approximately <NUM>.

<FIG> shows a further embodiment of the microwave safe RFID tag device <NUM> comprising a split ring (or shield) conductor <NUM> formed on one side of a substrate (or dielectric) <NUM>, a coil antenna conductor <NUM> formed on an opposite side of the substrate <NUM>, and a RFID chip <NUM>. In the microwave safe RFID tag device <NUM>, the split ring shield conductor <NUM> also acts as a HF bridge <NUM> between the center <NUM> and edge <NUM> of the coil antenna conductor <NUM> to make a continuous conductor to resonate with the RFID chip <NUM> at <NUM>. The bridging function is made by providing a low resistance (i.e., <NUM> ohm) path using crimped connections <NUM> between top and bottom conductors (i.e., shield conductor <NUM> and coil antenna conductor <NUM>), or other connective means such as plated through holes, etc., or any other suitable connective means as is known in the art. In the event that the shield conductor <NUM> is applied directly over the coil antenna conductor <NUM> as an additive conductor without a substrate <NUM> positioned in between, the connection may be made by a suitable conductive adhesive as is known in the art.

<FIG> show a further embodiment of the microwave safe RFID tag device <NUM> comprising two split ring shields (shield <NUM><NUM> and shield <NUM><NUM>), a HF RFID coil antenna conductor (or HF RFID inlay) <NUM>, and an RFID chip <NUM>. The microwave safe RFID tag device <NUM> comprises a first split ring (or shield) conductor (shield <NUM>) <NUM> with a gap <NUM> formed on the bottom edge <NUM> of the shield <NUM> conductor <NUM> and wherein the shield <NUM> conductor <NUM> is positioned on one side of the coil antenna conductor <NUM>. The microwave safe RFID tag device <NUM> also comprises a second split ring (or shield) conductor (shield <NUM>) <NUM> with a gap <NUM> formed on the top edge <NUM> of the shield <NUM> conductor <NUM> and wherein the shield <NUM> conductor <NUM> is positioned on the opposite side of the coil antenna conductor <NUM>.

By having the two shield conductors (namely, shield <NUM><NUM> and shield <NUM><NUM>) rotated relative to each other, the gaps <NUM> and <NUM> of the shield conductors (<NUM> and <NUM>) are positioned in different locations. Thus, although both of the shield conductors (<NUM> and <NUM>) do not present a shorted turn to the coil antenna conductor <NUM>, as the gaps (<NUM> and <NUM>) in shield <NUM> and shield <NUM> (<NUM> and <NUM>) are in different locations, no current flows in the coil antenna conductor <NUM> at either point as they bridge each other at <NUM>. Accordingly, the microwave safe RFID tag device <NUM> with two shield conductors (<NUM> and <NUM>) minimizes current flow in the coil antenna conductor <NUM>.

<FIG> shows a further embodiment for a microwave safe RFID tag device <NUM> comprising a split ring (or shield) conductor <NUM> formed on one side of a substrate (or dielectric) <NUM>, a coil antenna conductor <NUM> formed on an opposite side of the substrate <NUM>, and a RFID chip <NUM>. In the microwave safe RFID tag device <NUM>, the coil antenna conductor <NUM> also acts as a HF bridge <NUM> between the center <NUM> and edge <NUM> of the coil antenna conductor <NUM> to make a continuous conductor to resonate with the RFID chip <NUM> at <NUM>. The bridging function is made by providing a low resistance (i.e., <NUM> ohm) path using crimped connections <NUM> or other connective means such as plated through holes, etc., or any other suitable connective means as is known in the art.

Furthermore, the coil antenna conductor <NUM> comprises small gaps <NUM>, in the region of <NUM> to <NUM> or any other suitable size as is known in the art. The small gaps <NUM> are used to isolate the turns of the coil of the coil antenna conductor <NUM>. As the gaps <NUM> are small, the coupling capacitance between coil turns is a low impedance at <NUM>, making the coil of the coil antenna conductor <NUM> look like a solid ring at <NUM> with no gaps to prevent arcing.

<FIG> discloses an embodiment of the microwave safe RFID tag device <NUM> comprising a RFID chip <NUM> connected to a strap <NUM>, wherein the RFID chip <NUM> and strap <NUM> are positioned on a coil antenna conductor <NUM>, and a split ring (or shield) conductor <NUM> is formed on top of the RFID chip <NUM> and strap <NUM>. Specifically, the RFID chip <NUM> is connected to two lines <NUM> and two pads <NUM> designed to connect (or bridge) it to the center <NUM> and outside edge <NUM> of the coil antenna conductor <NUM>, giving a resonant circuit. The bridging (or connection) function is made by using crimped connections <NUM> or other connective means such as plated through holes, etc., or any other suitable connective means as is known in the art to connect with the two lines <NUM> and two pads <NUM> of the RFID chip <NUM>.

Further, the strap <NUM> incorporates a top shield metalization which creates a shielded strap <NUM>. This shielded strap <NUM> acts as a continuous conductor over the coil antenna conductor <NUM>. Additionally, the shield conductor <NUM> comprises a split ring (or gap) <NUM> as described above and is placed on top of the coil antenna conductor <NUM>, with the gap <NUM> in the ring (or shield) conductor <NUM> shorted across at <NUM> by the shielded strap <NUM> and capacitive coupling. Thus, this microwave safe RFID tag device <NUM> prevents any current from flowing in the coil antenna conductor <NUM> at the point where there is the gap <NUM> in the split ring shield conductor <NUM> to prevent arcing.

Importantly, data contained on RFID chip <NUM>, such as "use by" or "consume by" data may be combined with other data, either from the manufacturer or relating to a particular user, to activate different cooking parameters, authorization levels necessary to override a cooking parameter, etc. Data relating to the user can include, but is not limited to, information regarding allergic reactions, time of day when cooking, age of the user, etc. This data, along with the manufacturer data and/or product data, acts to control if a particular microwave operation (e.g., thawing, heating, reheating, cooking, etc.) is authorized and, in the event it is not directly authorized, it requires further action from the user. Said further action by a user can include entering a password, using a RFID card, using a near field communication (NFC) enabled phone, etc., or any other suitable action as is known in the art for taking action.

More specifically, the process may begin with RFID tag <NUM> being read or interrogated and data concerning the RFID tagged product collected and analyzed. RFID tag <NUM> may be read or interrogated either inside or outside of the microwave cavity, depending on the particular RFID reader system being utilized. Based on said gathered data it can then be determined if the data read from RFID tag <NUM> shows that the tagged product is out of date (i.e., beyond its "best if used by" or "consume by" date). If the product is not out of date, then the microwave process can continue and the microwave oven control panel controls the appropriate microwave function (e.g., thawing, heating, reheating or cooking) on the RFID tagged product. If, on the other hand, the product is out of date then, it may be further determined if the product is a critical product. Whether a product is a "critical product" can be defined by any number of user specified parameters. For example, "critical products" could include baby products, products that tend to cause food poisoning if out of date, etc. If the product is not a critical product, then the microwave process could proceed directly to the desired microwave function (i.e., thawing, heating, reheating, cooking, etc.) and the microwave oven control panel controls the desired microwave function.

For example, if the RFID tagged product is beyond its "best before date" (i.e., is out of date), but is not a critical product (e.g., based on a low probability of food poisoning), for example, vegetables, the microwave oven could proceed directly to the desired microwave function. This may occur with or without other parameters from the RFID tag, such as cooking instructions. If, on the other hand, the product is both out of date and a critical product then a manual override or some form of verification may be required to continue. For example, if the product was to fall into a critical product category, for example shellfish or baby food, the microwave oven would require further authorization to override the lock out, such as a password. The same process could apply to products of food items containing allergens. If a user had previously defined that a person with an allergy to, for example, peanuts might be using the microwave oven, any products presented to the microwave oven containing peanuts would require a high-level over-ride (e.g., a password) and possibly sound an alarm.

Another aspect could relate to the age of the user. For example, a product that indicates that it becomes very hot during cooking, such as those containing high-levels of sugar syrup, would require an over-ride if children were present in the house to prevent the child from overheating the food product and suffering burning or scalding from the same. After further authorization occurs, the process then proceeds directly to the desired microwave function (e.g., cooking, thawing, heating, reheating, etc.), and the microwave oven control panel controls the microwave process on the RFID tagged product. As previously discussed, differing levels of authorization could be established depending on the critical nature of the issue and/or the particular needs of the user.

As previously discussed, RFID tag <NUM> may further comprise some form of sensor. For example, sensor can be a temperature sensor that can indicate if the RFID tagged product is thawed, chilled or frozen, or any other sensor as is known in the art, such as a moisture sensor, etc. Based on the sensor state and RFID data, the microwave oven can then select an appropriate cooking method (i.e., based on whether the food item is, for example, already thawed, chilled or frozen) as determined by the oven controller which then utilizes the data read from the RFID tagged product to select the appropriate microwave function to be performed.

For example, for frozen food products, the output from the sensor could be used to instruct the microwave oven controller to first thaw the food product at one microwave power setting, and then cook the food product at a different power setting. Alternatively, if the food product is determined by the sensor to already be thawed, the sensor output may be used to instruct the microwave oven controller to bypass the thaw process, and proceed straight to the cooking process, thereby saving both time and the energy necessary to operate the microwave oven during the thaw process, which is not necessary in this particular application.

Additionally, tag data obtained from RFID tag <NUM> may trigger a look up from an online web service or external database for the correct cooking parameter for that specific food item. Specifically, the microwave oven controller may send user interface data to an online system/web service or external database to obtain additional information about the food item and how to prepare the same. For example, the web service can provide additional information regarding the food item, such as tips on how to best cook the food item in the microwave, the appropriate power setting to use, or whether the food item is better cooked thawed, chilled or frozen, etc. The cooking parameters can then be combined with user preferences for some food items, for example, preferences such as the state of how the meat should be prepared, or the desired softness of vegetables, bread, etc. The oven controller may then utilize both the cooking parameters from the web service or other external database along with the user preferences to control the microwave cooking process of the food item.

<FIG> illustrates another embodiment of the present invention. <FIG> illustrates an alternative form of shield to the split rings described previously; as illustrated, the alternative form is a startburst <NUM>, a series of lines radiating from a central point inside the coil to the space outside the coil. The line widths are made so that they give adequate coupling, such as capacitive coupling, to the lines of the coil so that they are shorted at <NUM>, terminating the gaps in small arcs in the spaces between the gaps <NUM>, but provide a relatively low coupling between the coils of the HF antenna to maintain performance, if the gaps are kept to a small proportion of a wavelength <NUM>, for example lambda/<NUM> or smaller, they interaction between the gaps and the <NUM> energy is minimized. It will be appreciated that the number of arms on the starburst can vary depending on the required level of termination of the gaps.

Claim 1:
A radio-frequency identification, RFID, tag tolerant of microwave emissions at <NUM> (<NUM>) comprising:
a RFID chip (<NUM>);
an antenna conductor (<NUM>);
a split ring conductor (<NUM>); and
a dielectric (<NUM>) positioned between the antenna conductor and the split ring conductor,
wherein the antenna conductor comprises a gap (<NUM>) and the RFID chip is positioned in the gap, and
characterised in that a path connects the split ring conductor formed on one side of the dielectric and the antenna conductor formed on an opposite side of the dielectric, so that the split ring conductor acts as a HF bridge (<NUM>) between a center (<NUM>) and an edge (<NUM>) of the antenna conductor.