WO2015056048A1

WO2015056048A1 - Method for producing and modifying open or closed containers providing properties of an antenna

Info

Publication number: WO2015056048A1
Application number: PCT/IB2013/059351
Authority: WO
Inventors: Saulius RUDYS; Edvinas Baublys; Darius MONTVILA
Original assignee: Uab "Acorn Intelligence"
Priority date: 2013-10-14
Filing date: 2013-10-14
Publication date: 2015-04-23
Also published as: LT2013114A

Abstract

This invention relates to the technology of Radio-frequency Identification (RFID) which is used for the automatic identification of various objects or animals to which electronic labels (termed tags) are attached. It provides a method of producing and modifying an open or closed container providing properties of an antenna. Consequently, conductive container walls can be used as a basis for the slot type antenna by forming one or more slots in the container surface. In addition, slots are placed in the edges of a container and covered (coated) with dielectric band that reduces the risk of short-circuiting the slot antenna to a minimum. Such placement of the slots in the container edges ensures their minimal wear. Generally, a slot antenna radiates in the direction bisector between the two conductive surfaces when the angle between two sides of the slot reaches nearly 90 degrees which in many cases ensures an even distribution of electromagnetic field in the container volume. This arrangement also renders a maximum electromagnetic field strength in container corners that makes it easy to read-out RFID tags located in the corners of the container.

Description

METHOD FOR PRODUCING AND MODIFYING OPE OR CLOSED CONTAINERS PROVIDING PROPERTIES OF AN ANTENNA

FIELD OF INVENTION

This invention relates to the technology of Radio-frequency Identification (RFID) which is used for the automatic identification of various objects or animals to which electronic labels (termed tags) are attached. More specifically, it refers to radio frequency antennas used in RFID tag readers.

BACKGROUND OF INVENTION

Radio-frequency Identification (RFID) is an emerging technological labeling solution employed in warehousing and storage systems as well as used for labeling of consumer products, animals or individuals. This technology is based on electronic labels (tags) that commonly include a chip coupled to an antenna.

Identification of an individual tag is performed by sending the request signal and receiving an answer signal from a tag using a reader which has its own antenna and operates in a radio frequency domain. The individual tag automatically transmits a code that is held in the chip after receiving a query signal from a reader. Subsequently, the code is passed to the information system in which this unique code of the RFID tag is associated with information about the product to which the tag is attached. In this way it is possible to easily and reliably monitor the production process, shipping and item warehousing information. This technology can be employed in, for example, shopping carts, mail courier car trunks, trailers, train cars, freight containers and etc.

Nowadays, the most common antenna type used in RFID tag reader devices is a patch antenna which has been described by J. Q. Howell. Generally, it is a type of radio frequency antenna that consists of a rectangular sheet of a metal mounted at a specific distance above the larger sheet of metal (or the ground plate). This antenna can have a dielectric spacer between two metal patches as well as be made out of a metalized piece of a dielectric material (substrate) using commercial lithography processes. Subsequently, this structure is usually enclosed in a rigid plastic radome for an additional protection of the patch antenna. The main virtue of this structure is that the radio antenna has a low profile and can easily be mounted on a flat surface, for example container wall or a shopping cart bottom.

Generally, the main problem of actual applications of the patch antennae is connected with their placement inside a container. The antennae should be positioned on or near the container bottom in order to allow efficient read-out the tag information, because the commercially viable RFID tag/reader systems can successfully operate only in up to 10 or 12 meter distance. However, this kind of positioning increases the risk to damage the antenna during loading or unloading procedures, therefore non-protruding antennae are needed for this kind of placement. In order to prolong the lifetime of an RFID reader antenna and to cover a full inside volume of the container, both discovering the most appropriate way of placement of the antenna in the container and the type of the antenna itself are essential. To solve this problem, a number of possible solutions have been proposed.

A US patent No. US20110062234, published on 11-09-2009, describes an antenna device that includes a first conductive plate, a second conductive plate, arranged in parallel with the first conductive plate, which has at least one slot formed thereon, a power feeding element located between the first and second conductive plates to feed power to the first conductive plate, and a shutter configured to be movable to close/open the slot of the second conductive plate in order to change over a radiation area of radio wave radiated to communicate with RFID tags.

A US patent No. US2007017986, published on 19-07-2005, describes a device that includes a slot antenna having at least one slot disposed in a first substrate. A strap is disposed across the slot. The strap includes a second substrate and an integrated circuit. The integrated circuit is electrically coupled to the slot antenna. In a specific embodiment, a thickness of a metal slot antenna is at least 1/4 than inch. The RFID device can also be associated with a location, and be attached to a pallet rack.

A US patent No. US7830322, published on 27-06-2008, describes an antenna system for a reader configured to interact with RFID tags that includes one or more antenna elements electrically coupled to the reader for transmission and reception of RFID signals. In one embodiment the antenna elements include a conductive plate, a first elongate aperture in the plate oriented longitudinally in a first direction, a second elongate aperture in the plate oriented longitudinally in the first direction so as to be generally parallel with the first elongate aperture, a third elongate aperture in the plate oriented longitudinally in a second direction generally perpendicular to the first direction and configured to join the first and second apertures at about the longitudinal middle of the first aperture. In another embodiment the antenna element comprises a rectangular slot.

These prior-art patents describe RFID slot antennae that do not solve the problem of being non-protruding. Protruding antennae are susceptible to damage during the consumer product load or unload procedures to various containers or shelves in the warehousing or storage locations. The lifetime of the antennae described in these patents is increased only by using a metallic slot type structure that is stiffer than a plastic radome used to protect the conventional patch antennae from structural damage.

Other prior-art inventions, for example, PCT application No. WO2007140800, published on 06-06-2006, describes a metallic shelf that integrates an antenna which may be used for the automatic identification of products, especially the ones stored over punched and folded metal sheets that shape metallic shelves, so often used for logistical warehousing and product displaying in markets. This metallic shelf comprises at least one slot adapted to operate as a slot antenna, which is properly coupled to an RFID reader, for identification of each RFID tag attached to the objects supported on the said shelf. The slot antenna can be fed by a transmission line born in the RFID reader and to which this antenna is electromagnetic closely coupled, without any kind of contacts. The RFID readers can communicate, over a wired or wireless network, from the shelves to a core information system that processes data from the RFID tags. This prior-art patent describes rigid slot antennae that are incorporated into the shelves of storage locations. However, slot antennae mentioned in this patent do not have a dielectric layer on top of the conductive parts. Considering the most efficient placement of the antenna, that is on the bottom of a container or a shelve leads to a risk related to the accidental placement of a conducting product over a slot which would short-circuit the antenna and thus deteriorate its parameters.

Yet another prior-art invention patent No. US2004196152, published on 07-10-2004, describes a system to capture data regarding conditions in a sealed metal shipping container having: a sensor unit mountable inside the container and adapted to sense a condition inside of the container; an impulse radio transmitter receiving data from the sensor regarding the condition and transmitting an impulse radio wireless signal inside of the container; an impulse radio receiver external to the container and proximate the container, wherein the receiver is adapted to receive the impulse radio wireless signal propagating through the sealed metal shipping container, and a data device in communication with the receiver to capture the data from the sensor unit regarding the condition inside of the container. This prior-art patent employs a sensor unit which is mounted inside a container. This kind of placing of a sensor introduces protruding parts which could be damaged during the freight, cargo or consumer product loading or unloading procedures. One possible way to cope with this problem would be to use a sensor that completely covers the inside surface of the container, for example to use the whole container bottom as a ground plate and to mount a rigid metal sheet a specific distance above the container bottom thus making a container sized patch antenna, however it would pose problems regarding the matching of the transmission line with the patch antenna itself.

SUMMARY

In order to eliminate drawbacks indicated above, this invention provides a method of producing and modifying open or closed containers providing properties of an antenna. This invention employs a rigid slot type antenna illustrated in Fig. 1, which consists of an emitted radio signal wavelength size or bigger conductive plane (1) with a slot (2) in it. The transmission line or the electric circuit are coupled to two points (3) situated on different sides of the slot. An additional conductive layer (8) can be connected to the back side of the conductive plane (1) over a slot (2) as illustrated in Fig. 2, in order to achieve a unidirectional radiation of the antenna. Consequently, conductive container walls (4) can be used as a basis for the slot type antenna as illustrated in Fig. 3. In addition, slots (2) can be formed in the edges and corners of a container (4) and covered (coated) with a dielectric band (6) as is illustrated in Fig. 6 which would reduce the risk of short-circuiting the slot antenna (5) to a minimum. Such placement of slots in container edges ensures their minimal wear.

Generally, a slot antenna radiates into the bisector direction between the two conductive surfaces when the angle between two sides of the slot reaches nearly 90 degrees which in many cases ensures an even distribution of electromagnetic field in the container volume. This arrangement also renders a maximum electromagnetic field strength in container corners which makes it easy to read-out RFID tags located in corners of the said container.

DESCRIPTION OF DRAWINGS

In order to understand the invention better, and appreciate its practical applications, the following figures are provided and referenced hereafter. The figures are given as examples only and in no way limit the scope of the invention.

Figure 1: illustrates a bidirectional slot type radio frequency antenna (5);

Figure 2: illustrates a slot antenna (5) with an additional conductive surface (8) attached to the one side of the conductive metal plate (1) in which the slot (2) is formed;

Figure 3: illustrates possible ways of slot antennae (5) arrangement on the open container walls (4);

Figure 4: illustrates the possible ways of slot antennae (5) arrangement on edges of closed containers (4);

Figure 5: illustrates the possible ways of slot antennae arrangement (5) on edges and in corners of open containers (4);

Figure 6: illustrates placement of the dielectric coating (6) over the slot (2) which reduces a risk of short-circuiting the slot antenna (5);

Figure 7: illustrates the general principle of equipping freight containers which are already in use by attaching parts which together with the corrugated surface of the said container (9) make up a system of slot antennae;

Figure 8: illustrates possible ways of equipping the freight container with antennae (5) that directs radiation into the said container volume.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the most preferred embodiment, this method is used to produce and modify open or closed container of any shape (4). Slots (2) having dimensions consistent with the radio frequency used for RFID tag read-out are formed in the conducting container surface (4). Generally, this type of container with slots (2) can act as a system of RFID tag reader antennae (5) which could be then employed to read-out the tag information related to the products or cargo enclosed in the said container.

In another preferred embodiment, the slots (2) are formed in the edges of the container which in turn ensures their minimal wear. Consequently, placement of an antenna (5) in the edge of the container ensures an even distribution of electromagnetic radiation inside the container volume and maximum electromagnetic field strength in the corners. In addition, slots (5) can be covered with a dielectric band (6) in order to minimize the risk of short-circuiting the slot antenna (5) without making any protrusions on the surface of the container.

In yet another preferred embodiment, this method is used to modify a freight container designed to transport products and materials. A corrugated metal surface of a container (9) to which a metal conductive plate (1) with a slot (2) is attached and together with a cavity (7) constitutes an unidirectional slot antenna. Unidirectional radiation can be achieved both by attaching the said metal plate (1) with a slot (2) in it over the ridge between the two furrows of the container surface (9) or by cutting a slot in the furrow of the container surface (9) and attaching a metal plate (10) without any slots between the two ridges.

In another preferred embodiment, both the arrangement in which antennae (5) are radiating into the volume of the freight container and the arrangement in which the radiation is directed outward of the container volume can be combined. Both arrangements are realized by arranging the unidirectional slot antennae (5) antiparallelly relative to each other or by simply forming a bidirectional antenna (5) on the container surface (9).

While this invention is described in terms of certain embodiments thereof, it is not intended to be limited to the description above, rather only to the extent set forth in following claims.

Claims

A method for producing or modifying an open or closed conductive container (4) of any form, characterized in that one or more slotted holes (2) of any form are formed in any way in the surfaces of the said container and/or any conductive surfaces (8) that are attached to the said container providing the said container with functionality of a slot antenna (5) or system of slot antennae.
The method according to claim 1, characterized in that the said container (4) has said conductive surfaces (8) attached to the said container (4) over said slotted holes (2).
The method according to one of the claims 1 or 2, characterized in that said slotted holes (2) are formed in any way on edges and/or corners of the said conductive container (4).
The method according to one of claims 1 to 3, characterized in that said slotted holes (2) are formed on said container having a corrugated surface (9).
The method according to one of claims 1 to 2, characterized in that said slotted holes (2) are covered with a dielectric band (6).
The method according to one of claims 4 to 5, characterized in that said slotted holes (2) are formed in any way on furrows and/or ridges of said container having a corrugated surface (9).
The method according to one of claims 1 to 6, characterized in that said conductive surfaces (8) with or without said slotted holes (2) are attached between at least two furrows or said ridges of said container having a corrugated surface (9).
The method according to claims 1 to 7, characterized in that said conductive surfaces (8) without said slotted holes are attached over the said ridge or said furrow with a said slotted hole (2).
The method according to claims 1 to 7, characterized in that said conductive surfaces (8) with said slotted holes (2) are attached over the said ridge or said furrow without a said slotted hole.