Arrangement for reducing interference in an electronic shelf label

Abstract

An arrangement for reducing interference in a wireless electronic shelf label (ESL) (100) having a layered structure the ESL comprising: a display layer (101) comprising display material, a circuit board (203) with a backplane material structure and an antenna (202), and a circuit board arrangement with control electronics for controlling the operation of the label, such as the display and the radio communication, and a resilient layer having a space for a rigid component, such as a battery, wherein said resilient layer is arranged to provide a substantially even total thickness of said label (100), wherein the radio communication control further comprises means for radio frequency communication via modulated backscatter, wherein the arrangement is ring resonator arrangement isolating the ESL from the electrically conducting shelf arranged on the antenna circuit board, the ring resonator arrangement comprising a plurality of ring resonators (204) that are electrically isolated from the antenna and arranged at least on the side nearest the shelf when the ESL is attached to the shelf.

Claims

1. A wireless electronic shelf label (ESL) having a layered structure comprising: a display layer comprising display material, an antenna circuit board with a backplane material structure, a far field antenna disposed on the antenna circuit board, a circuit board arrangement with control electronics for controlling the operation of the label, including the display and radio communication control, and a resilient layer having a space for a rigid component, such as a battery, wherein said resilient layer is arranged to provide a substantially even total thickness of said label, wherein the radio communication control further comprises means for radio frequency communication via modulated backscatter, wherein the ESL further includes an arrangement for reducing interference which comprises a split ring resonator arrangement, arranged on the antenna circuit board to isolate the ESL from an electrically conducting shelf to which the ESL is attached, and wherein the split ring resonator arrangement comprises a plurality of ring resonators, as separate structures that are electrically isolated from the antenna but are printed on the same layer of the antenna circuit board and arranged at least on a side nearest the shelf to which the ESL is attached.

2. The wireless electronic shelf label according to claim 1, wherein the ring resonators are arranged at least on a common centre line that is parallel with an edge of the circuit board that is nearest the shelf.

3. The wireless electronic shelf label according to claim 1, wherein the ring resonators have all the same diameter which is essentially smaller than the width of the ESL.

4. The wireless electronic shelf label according to claim 1, wherein the ring resonators may additionally be arranged on another side of the board.

5. The wireless electronic shelf label according to claim 1, wherein the split ring resonators comprise a ring and an opening in the ring, whereby the ring operates as an inductor and the opening as a capacitor.

6. The wireless electronic shelf label according to claim 1, having an arrangement for reducing the interference.

7. The wireless electronic shelf label according to claim 6, wherein the antenna and the split ring resonators are arranged on separate sides of a circuit board or on separate circuit boards arranged onto each other.

8. The wireless electronic shelf label according to claim 6, wherein the circuit board for said antenna and control electronics is flexible.

9. A wireless electronic shelf label according to claim 2, having an arrangement for reducing the interference.

10. A wireless electronic shelf label according to claim 3, having an arrangement for reducing the interference.

11. A wireless electronic shelf label according to claim 4, having an arrangement for reducing the interference.

12. The wireless electronic shelf label according to claim 7, wherein the circuit board for said antenna and control electronics is flexible.

13. The wireless electronic shelf label of claim 3, wherein the split ring resonators have a diameter which is less than 20% of the width or length of the circuit board.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The foregoing, and additional objects, features and advantages of the present invention will be more clearly understood from the following detailed description of preferred embodiments of the present invention, taken in conjunction with accompanying drawings, in which:

(2) FIG. 1 presents an electronic shelf label system for displaying product pricing on shelves,

(3) FIG. 2 presents an ESL module according to the present invention together with a plastic holder, and

(4) FIGS. 3a and 3b present the antenna circuit board according to the present invention in a top view and a ring resonator in more detail.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(5) FIG. 1 shows an ESL (Electronic Shelf Label) system utilizing ESL's 100 implemented as a semi-active tag in a supermarket or similar sale environment where the shelves 101 are equipped with ESL displays that are typically attached in shelf rails carrying plastic ESL holders 102. ESL displays are placed in locations corresponding to the products on the shelves to be easily perceivable for the customers.

(6) ESL displays communicate in a wireless manner with the base stations 103. This wireless communication method may is based on passive backscatter radio communication. In this approach the base stations actively send radio signals and instead of answering with active radio transmission, the ESL modules do not use a radio transmitter; instead, they answer by modulating the reflected power of the base station signal. The modulation is achieved, typically, by changing the load state of the ESL antenna in the ESL module, for example, by connecting and disconnecting the antenna between the ground and non-ground potential. This modulation of the backscattered signal allows for the ESL modules to answer to the base stations and further to the store level server 104.

(7) Each ESL module can be identified by its own identification code that the ESL module in question knows to listen for in the transmission from the base station. After receiving new information, instructions or commands from the store server via bases station, the ESL module can acknowledge the reception of these instructions by using the reflected backscattering modulated properly and timely for the store level server to identify that the response is coming from the ESL module is question. To facilitate that the store server may have a certain listening period after a transmission directed to a certain ESL module for giving the module possibility to answer during that time.

(8) Base stations are typically connected in a wired manner, for example, via Ethernet connection or via WLAN or corresponding wireless communication connection to a base station controller 105. This base station controller is further connected to controller software running in a store level server containing the price and other product information. Some retail chains may have the server only in the head office.

(9) When price information is changed in the store level server locally according to pre-programmed instructions therein or manually by the shopkeeper or, remotely, from instructions received from a store chain level server 108, this information will be delivered through the base stations to individual ESL displays. The corresponding price information is also made available to the check-out counter 106 that is arranged in communication with the store level server. A further possibility for modifying the content of the information send to individual ESL displays is the use of a handheld terminal 107. A handheld terminal can be used by a member of the shop staff allowing him/her to freely move around in the shop and communicate in a wireless manner with the store level server and POS system. This communication can be achieved via a wireless communication network allowing using Personal Digital Assistant (PDA) type computing devices with inherent wireless communication capabilities. The handheld terminal can contain only limited functionalities or depending on the processing power of the device, it can be used to control the full capabilities of the application running in the store level server. In some applications in smaller shops with a fewer number of ESL displays, a handheld terminal may be used instead of a separate store level server. A mobile phone may also be used as a contacting means to the POS and further to the pricing system, too.

(10) Further, the shop level server can be in connection with a chain level server that can provide identical price and product information to several stores belonging to the same chain of stores.

(11) FIG. 2 shows an ESL display module 100 together with a plastic clip holder 200 where the display module is attached to the clip holder 200. The holder 200 can be attached, typically, to the front rail of a shelf and facilitates easy installation of the ESL display. The ESL module may also be attached directly to the shelf or to a self edge rail other structure without a separate holder.

(12) In the example embodiment in FIG. 1, the size of the ESL module is approximately 90 mm (width)45 mm (height)2 mm (thickness). This gives the display module, or label a convenient size for convenient manual handling, occupying a suitably sized space in the shelf and also large enough text and numbers to be easily visible for a customer.

(13) The above dimensions are just exemplary giving idea of the size class of the module. The size of the modules according to the invention can vary from these according to the application.

(14) The ESL display module 100 in FIG. 2 has a layered structure. It consists essentially of a flexible epaper display layer 201 comprising epaper display material, a backplane layer as a flexible circuit board having an electrode structure (not shown) for controlling the display, a substantially rigid battery, wherein the thickness of said rigid battery is greater than the thickness of said flexible display layer and the thickness of said flexible backplane layer, and a resilient layer having a cut-out space for said rigid battery, wherein said resilient layer is arranged to provide a substantially even total thickness of said device.

(15) The module further comprises wireless communication capabilities with an antenna 202 consisting of two triangular antenna patterns on the same flexible circuit board 203 as the display control (FIG. 3a), as the ESL is implemented as semi-active RF tags that is powered from incident RF communicating via modulated backscatter, and a separate flexible circuit board.

(16) The rigid accumulator has been encapsulated in a cut-out space by laminating said display, backplane, control circuit board and resilient layers together. Further, the display layer, the backplane layer, the resilient layer and the rigid accumulator are located between two protective layers. The rigid component has been attached to the separate flexible printed circuit board operating as a sub-module under the backplane and the antenna.

(17) Manufacturing of the ESL's is implemented basically on the web-type roll-to-roll manufacturing methods that is not described here in detail as it is not essential for this invention. The continuous web-shaped product may be die cut into individual labels 100.

(18) The backplane and the antenna circuit board 203 and the ESL control circuit board are patterned plastic films (PET or PC or PVC or polyimid) with patterned conductive copper layers. The forming and patterning of the conductors can be made using any method known as such for a person skilled in the art, for example by direct printing of conductive ink or by etching of a thin metal layer. The lower surface of the backplane has display segment feed lines patterned in a similar way. Each display segment is electrically connected to a corresponding display segment feed line for example through a preferably laser processed via. Also other ways of providing feed-through vias are possible as is evident for a person skilled in the art. In order to establish an electrical contact from the backplane segments to the display front electrode, that is in this example on the front surface of the flexible electronic display web, an electrically conducting tape is laminated on the backplane area acting as a front electrode feed line. Alternatively and instead of an electrically conducting tape, electrically conducting paste or similar material with adhesive nature may be dispensed on the backplane web to make contact with the front plane electrodes.

(19) Further, according to the present invention the ESL is electrically isolated from the metal shelf by providing a plurality of small ring resonators 204, that are electrically isolated from the antenna, on the antenna circuit board between the shelf and the antenna, ie. on the side of the antenna circuit board that is nearest the shelf. The ring resonators comprise a ring 210 and an opening 211 in the ring whereby the ring operates as an inductor and the opening as a capacitor. The ring resonators are all arranged on the common centre line 205 that is parallel with the edge 206 of the circuit board that is nearest the shelf. The ring resonators have all the same diameter that is essentially smaller than the width of the ESL, typically 5-10 mm. In this way the interference from the shelf can be significantly reduced and the RF operation of the ESL improved. The ring resonators may additionally be arranged on an other side of the board, for instance at the antenna coupling end near the antenna signal connect points 207 on the circuit board.

(20) As a further advantage, the manufacturing process according to the invention gives possibility to manufacture display labels that can be made curved in shape. This can be done by adjusting the tension between the different laminated layers together with proper selection of materials. The upper surface of the display label 100 may be e.g. convex or concave.

(21) The invention provides possibility to manufacture display module structures that despite of their significant thickness, at least more than 1 mm but typically in the range of 2 mm, have certain amount of flexibility and still maintain well their original shape, Further, the encapsulated display modules 100 can be made very light compared to their size, which makes the convenient and easy to handle both manually and automatically. In prior art products and encapsulation methods, increasing thickness typically decreases the flexibility, whereas in the products according to the invention the flexibility and the benefits therein are preserved better even if conventional rigid components are to be used as a part of the device ESL.