MICROSTRIP PATCH ANTENNA APPARATUS AND METHOD

[0001] This application claims the benefit of prior U.S. Provisional Application No. 60/590,430, filed July 23, 2004, which is hereby incorporated by reference in its entirety. This application is related to U.S. Patent Application Nos. 10/338,892; 10/348,941; 60/346,388; 60/350,023; and 60/466,760, is also related to PCT Application No. PCT/US04/13809. The disclosure of each of the above mentioned applications is expressly incorporated herein by reference in their respective entireties.

BACKGROUND

[0002] As explained in detail in PCT Application No. PCT/US04/13809, inventory management is becoming increasingly important in today's growing economy. Although this growth provides consumers with more choices for selecting various goods and services, businesses (e.g., retailers, wholesalers, etc.) are tasked with managing this growing inventory.

[0003] To manage growing product inventories, businesses have implemented perpetual type inventory management systems, which are systems that use Point Of Sale (POS) data on products sold, invoicing data, and historical data on inventory 1 #1956817 Docket No.: M3405.0013/PO 13 (PATENT) audits or cycle counts (e.g., periodic inventory counts of products) to determine the inventory that exists within the walls of a retail store. POS data generally refers to data generated at a checkout system (e.g., cash register). Based on the inventory level within the retail stores, products may be reordered from a manufacturer. Alternatively, the manufacturer and retailer may have an agreement that directs the manufacturer to preemptively deliver products according to the terms of the agreement.

[0004] Although perpetual inventory management systems alleviate some of the burden in managing large inventories, they may inject inaccuracies in cycle counts, POS scanning data, redundant re-ordering, misdirected shipments, and/or unusual sales velocity (i.e., the sale of products that take place either too fast or too slow).

[0005] Another shortcoming associated with perpetual inventory management systems includes inventory shrinkage, also described as the reduction of inventory due to non-sale circumstances. For example, shrinkage may occur at any point in a supply chain, stemming from invoice errors, vendor fraud, misdirected shipments, retail employee theft and customer theft. If inventory is computed as described above (i.e., using perpetual inventory management techniques), shrinkage rates (amounting to several percent of sales) can cause divergence of perpetual and physical inventory.

#1956817 Docket No.: M3405.0013/P013 (PATENT) [0006] To address the shortcomings of conventional inventory management systems, businesses have begun to incorporate wireless identification devices to assist in managing the inventory of products. This advancement contemplates attaching Radio Frequency Identification (RFID) tags on products during manufacture or when the products are stored in a warehouse. Each RFID tag includes an Integrated Circuit (IC) that enables the tag to have a unique identification number. Therefore, when a product is taken from a warehouse and placed on a retail shelf, for example, the products may be scanned to give a comprehensive inventory. Further, RFID tag technologies have been contemplated in providing distributed inventory management between a manufacturer and a retailer. For example, a manufacturer may be alerted through the Internet each time a product is sold at a retailer using the information stored in the product's RFID tag. The manufacturer may then use this information to forecast replenishment schedules with the retailer to prevent an out-of-stock situation.

SUMMARY

[0007] An apparatus (and corresponding method) is provided in the form of a patch antenna useful in any number of antenna applications. In a preferred embodiment of the invention, for example, the patch antenna may be used for writing (and reading) identifying information to (and from) RFID tags. The identifying information may be

#1956817 Docket No.: M3405.0013/P013 (PATENT) used to perform various inventory management processes. In accordance with a preferred embodiment of the invention, the writing of item information may include writing to the RFID tags an electronic product identification code (EPIC) that may contain item specific information (e.g., item characteristics such as color or shape, manufacturer and stock number and/or a serial number unique for that particular combination of manufacturer and stock number). The patch antenna may be used in an EPIC writer or "Tag burner," in a variety of processes where it may be useful for writing or reading RFID tags, or in any other suitable antenna application.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIGs. IA and IB illustrate a known patch antenna made with a coaxial feed;

[0009] FIGs. 2A and 2B illustrate a known patch antenna made with a microstrip feed;

[0010] FIGs. 3A and 3B illustrate a patch antenna in accordance with a preferred embodiment of the invention;

[0011] FIG. 4 illustrates exemplary form factors of a patch antenna in accordance with a preferred embodiment of the invention;

[0012] FIG. 5 illustrates an exemplary Tag Burner apparatus; and 4 #1956817 Docket No.: M3405.0013/P013 (PATENT) [0013] FIG. 6 illustrates an exemplary use of the patch antenna within a Tag Burner apparatus in accordance with a preferred embodiment of the invention.

DETAILED DESCRIPTION

[0014] Preferred embodiments and applications of the invention will now be described. Other embodiments may be realized and changes may be made to the disclosed embodiments without departing from the spirit or scope of the invention. Although the preferred embodiments disclosed herein have been particularly described as applied to the field of RFID systems, it should be readily apparent that the invention may be embodied in any technology having the same or similar problems.

[0015] Various embodiments of the invention provide an intelligent inventory management process to monitor and collect information associated with an inventory of items. An "item," as the term is used herein, may include any type of product (or other tangible object) that is manufactured, developed, grown by an agricultural business, or otherwise provided or utilized by a manufacturer, supplier, retailer, individual, or other entity.

[0016] The information that is collected, for example, using systems and methods described herein, may be used to perform various inventory management processes that enable a user to control the inventory of items, monitor amounts of inventory, 5 #1956817 Docket No.: M3405.0013/P013 (PATENT) facilitate and identify recalled or defective items included in the inventory, manage the misplacement of items, and receive alert messages associated with a variety of inventory conditions, such as security conditions, out of stock conditions, etc.

[0017] Preferred embodiments of the invention utilize a "patch antenna." The term "patch antenna" can refer to a small antenna made up of a two-dimensional pattern or element (known as a "patch"). A patch antenna design is one exemplary form factor that may be used as an antenna in a variety of communication applications (e.g., RF applications such as UHF transmissions). FIGs. IA and IB (cross-sectional view) show a known patch antenna that includes a conductive patch 100 separated from a ground plane 120 by a dielectric 110. A feed line such as coaxial cable 130 leads to connector 140 on the side of the ground plane that is opposite from patch 100. The ground sheath of the coaxial cable 130 may be joined via connector 140 to the ground plane 120, while the coaxial cable center (signal) conductor may be joined via connection 150 to the patch 100 (e.g., through solder joint 160).

[0018] FIGs. 2A and 2B (cross-sectional view) show another patch antenna that includes a conductive patch 200 separated from ground plane 220 by a dielectric 210, similar to that shown in FIGs. IA and IB. An antenna feed may include coaxial cable 230 that leads to microstrip 240 (e.g., on substrate 242) on the side of the ground plane that is opposite from patch 200. The ground sheath of the coaxial cable 230 may be 6 #1956817 Docket No.: M3405.0013/P013 (PATENT) joined via connector 234 to the ground plane 220, while the coaxial cable center (signal) conductor may be joined via connection 232 to the microstrip 240. The signal conductor may be joined through the microstrip 240 to patch 200 through connection 250 (via, for example, solder joint 260).

[0019] In accordance with a preferred embodiment of the invention, a patch antenna is provided, as shown in FIG. 3A, with a conductive patch 300 in a particular pattern or geometrical shape (e.g., square, rectangular, circle, etc.). The patch antenna may be, for example, a multilayer device. Patch 300 may be made up of a metal, foil, or other equivalent material (e.g., film, plate, substrate, etc.), and is separated from ground plane 320 by a dielectric 310. Preferably, the dielectric is made up of a substrate material (e.g., as is used for printed circuit boards), air, and any other material having negligible electrical conductivity (including a combination of such negligibly conductive material). As illustrated, an antenna feed can be provided having a first portion 330 (e.g., coaxial cable) and a second portion 340 (e.g., a microstrip which may be mounted on substrate 342). Alternatively, the second portion 340 may be a microstrip mounted on dielectric 310.

[0020] In accordance with a preferred embodiment of the invention, microstrip portion 340 (as formed on substrate 342) is preferably a device having first and second distal ends respectively connected to patch 300 and coaxial cable 330 (e.g., at signal line 7 #1956817 Docket No.: M3405.0013/P013 (PATENT) 332). Preferably, (second layer) microstrip 340 is coupled to or otherwise located between (first layer) patch 300 and (third layer) dielectric 310. Also, in accordance with a preferred embodiment, microstrip 340 is formed from a plurality of segments electrically coupled together to provide RF signals to/from patch 300. As shown in FIG. 3A, for example, microstrip 340 is formed from a strip having a gap between two segments. Preferably, an impedance matching circuit 370 is provided to join (or bridge together) one or more of the plurality of microstrip segments 340. The impedance matching circuit 370 may include one or more electrical reactance components (e.g., capacitors) to provide impedance matching for the circuit. Impedance matching circuit 370 may alternatively be placed at either distal end of (or anywhere within) the feed line to provide the appropriate impedance matching for the circuit.

[0021] Preferably, microstrip 340 is provided with a ground plane 320 (e.g., the fourth layer) preferably coupled to or otherwise located next to dielectric 310 (third layer). In one embodiment, the ground sheath of the coaxial cable 330 may be joined via connector 334 to the ground plane 320, while the coaxial cable center (signal) conductor may be joined via connection 332 to the microstrip 340 as illustrated in Figure 3A. The signal conductor may be coupled through the microstrip 340 to patch 300 (through connection 350 and, for example, solder joint 360).

#1956817 Docket No.: M3405.0013/P013 (PATENT) [0022] FIG. 3B shows in cross section an exemplary embodiment of the invention where patch 300 is separated from ground plane 320 by a spacing height h, which may be filled, for example, by air or any other dielectric material. Preferably, height h is predetermined to be at least the combined height of microstrip 340 and substrate 342. (In an exemplary implementation, the height h is made up mostly of air.) The patch 300 may be supported on one or more supports 380. For example, support 380 may be a support such as post, or other structure, located in the center of patch 300. One or more non-conductive (insulating) supports may be utilized at any position on the patch 300. The patch 300 may also be supported by attachment to other nearby structures or surfaces.

[0023] The height h, the patch area, and the patch shape may be determined using a variety of factors. In a preferred embodiment, these parameters take into account the antenna frequency bandwidth, antenna efficiency, working frequency, and polarization requirements of a particular implementation. The feed microstrip line can be formed on a PCB substrate in air or other dielectric material. An example characteristic impedance is 50 ohms.

[0024] Although patch 300 (FIG. 3A) is shown having a square shape, any shape (symmetrical or non-symmetrical) may be used in accordance with the invention (e.g., square 400, rectangle 401, circle 402, oval 403, square with clipped corners 404, circle 9 #1956817 Docket No.: M3405.0013/P013 (PATENT) with tabs 405, circle with notches 406, and circle with apertures 407, as illustrated in FIG. 4).

[0025] FIG. 5 illustrates an exemplary implementation of a preferred embodiment of the invention. In this exemplary implementation, the patch antenna described herein may be used as the antenna in "Tag Burner" 500 for writing and reading RFID tags, as previously described in U.S. Provisional Application No. 60/466,760 (and in PCT Application No. PCT/US04/13809), hereby incorporated by reference in their entireties.

[0026] FIG. 5 shows a bar code scanner 520, antenna housing 550, and visual indicators representative of user interface devices 530. Also shown is an exemplary item 570 having an RFID tag 560 and bar code 565. An optional support arm 521 may be used to hold the bar code scanner 520 in a position for readily scanning the bar code 565. It should be understood that other orientations may be possible for the item. For example, item 571 having an RFID tag 561 in a different location on the item, and a bar code 566 is shown in another orientation.

[0027] FIG. 6 shows an exemplary embodiment of the invention, wherein an antenna housing 550 contains a patch antenna. The patch antenna includes a plate 600, which may be supported, for example, on a lower cover 610 from which it may be separated by a distance 620, for example, by standoffs or other devices represented by 10 #1956817 Docket No.: M3405.0013/P013 (PATENT) 630. The lower cover 610 may be fastened to the antenna housing 550, for example, with screws at points 615. An optional center hole 640 is also shown in the plate 600, providing access for another attachment means, if desired, between lower cover 610 and antenna housing 550. A connection means 650, such as microstrip, coaxial cable, etc., described herein, may be used to connect the plate 600 to a connector 660 such as a coaxial cable connector, for transmission and/or reception of an RF signal used by other components (not shown) of the Tag Burner 500.

[0028] The following summarizes an exemplary operation of the Tag Burner 500 (FIGs. 5 and 6) using the patch antenna in accordance with an exemplary implementation of a preferred embodiment of the invention. (Additional exemplary description of the operation of the Tag Burner itself is provided in U.S. Provisional Application No. 60/466,760 and in PCT Application No. PCT/US04/13809.) In an exemplary operation, Tag Burner 500 (FIGs. 5 and 6) determines whether there is an item 570 (or RFID tag 560) within range of the patch antenna. If the item 570 (or RFID tag 560) is detected (e.g., using the patch antenna), the Stock Keeping Unit (SKU) number or other identifying information about the detected item 570 can be inputted. Typically, this input is provided by scanning bar code 565 using bar code scanner 520. If it is determined that an EPIC number is to be written to RFID tag 560, the desired EPIC number is obtained and transmitted over the patch antenna to item 570 (and RFID

11 #1956817 Docket No.: M3405.0013/P013 (PATENT) tag 560) to write the EPIC number to RFID tag 560. The RFID tag 560 can then be read using the patch antenna to verify that the EPIC number has been written properly.

[0029] Those of ordinary skill in the art would recognize and fully appreciate the inventive method of making and using a patch antenna from the mere description of the embodiments and implementations of the patch antenna as provided in this disclosure. No further detailed description of such methods, therefore, is believed necessary. It should be further readily apparent that the patch antenna structure (as used for RFID applications or any other antenna applications) may be fabricated in any known manner, for example, on a printed circuit board.

[0030] While preferred embodiments of the invention have been described and illustrated, it should be apparent that many modifications to the embodiments and implementations of the invention can be made without departing from the spirit or scope of the invention. For example, although embodiments and implementations of the invention have been specifically illustrated herein as reading and writing RFID tags (e.g., antenna housing 550, tag 560, item 570), the invention may easily be deployed or embodied in any form of (RF- or non-RF-based) tag, and may also include the reading and writing of tags that have not yet been placed on a given item at the time of writing. Although a Tag Burner 500 has been illustrated, it should be apparent that the invention may be used in other form factors as well. 12 #1956817 Docket No.: M3405.0013/P013 (PATENT) [0031] The different structures and configurations described herein have been provided as exemplary of the possible embodiments and implementations of the invention and should not be deemed as a limitation on the invention. The support structure 380 shown in FIG. 3B, for example, is illustrated as a post positioned normal to the surface of ground plane 320. This support structure 380 may alternatively be positioned at any angle with any geometrical shape sufficient to maintain patch 300 the predetermined distance h from ground plane 320. In addition, the structures disclosed herein as being joined or coupled together (e.g., using solder joint 360 (FIG. 3A)), may be brought together using any known functionally equivalent means or technology (e.g., solder, weld, screw, bolt, adhesive, etc.).

[0032] While embodiments and implementations directed to an antenna structure for an RFID system have been disclosed, the invention may easily be deployed or embodied in any antenna-related environment or application (e.g., GPS receivers, etc.) in accordance with the teachings herein.

[0033] It is to be understood therefore that the invention is not limited to the particular embodiments disclosed (or apparent from the disclosure) herein, but only limited by the claims appended hereto.

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