GB2552294A

GB2552294A - Appliance receptacle

Info

Publication number: GB2552294A
Application number: GB1608831.2A
Authority: GB
Inventors: Robert Brown James; Robert Lawrence Christopher; Singh Rajinder
Original assignee: Qinetiq Ltd
Current assignee: Qinetiq Ltd
Priority date: 2016-05-19
Filing date: 2016-05-19
Publication date: 2018-01-24
Also published as: GB201608831D0

Abstract

A receptacle made substantially or totally from an electrically conductive material is adapted to promote transfer of energy within a defined frequency band emanated by a transceiver to receptive devices contained within the container. The devices are preferably RFID tags. The container may have a slot, cavity or aperture having a resonant frequency within the frequency band. Slots may be open slots 201 or closed slots (301, fig. 3), and may comprise one or more orthogonal connected slots. Cavities may be formed as a gap between spaced parts of the receptacle (see figure 4) or may comprise an array of spaced cavities (503, fig. 5a). The receptacle may include undulations formed of dielectric material which prevent the tags from contacting the receptacle wall (see figure 6a), and the undulations may include slots at their peaks (figure 6b). The receptacle may include coupling means (801, fig. 8) for spacing adjacent receptacles. The receptacles are preferably boxes, racks or trays, for example used to store surgical instruments having RFID tags.

Description

(54) Title of the Invention: Appliance receptacle

Abstract Title: Receptacle for remotely readable objects (57) A receptacle made substantially or totally from an electrically conductive material is adapted to promote transfer of energy within a defined frequency band emanated by a transceiver to receptive devices contained within the container. The devices are preferably RFID tags. The container may have a slot, cavity or aperture having a resonant frequency within the frequency band. Slots may be open slots 201 or closed slots (301, fig. 3), and may comprise one or more orthogonal connected slots. Cavities may be formed as a gap between spaced parts of the receptacle (see figure 4) or may comprise an array of spaced cavities (503, fig. 5a). The receptacle may include undulations formed of dielectric material which prevent the tags from contacting the receptacle wall (see figure 6a), and the undulations may include slots at their peaks (figure 6b). The receptacle may include coupling means (801, fig. 8) for spacing adjacent receptacles. The receptacles are preferably boxes, racks or trays, for example used to store surgical instruments having RFID tags.

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Appliance Receptacle

This invention relates to trays, racks, boxes and other receptacles for holding or supporting items. More particularly, it relates to such means where the items being held or supported may have a radio frequency readable tag located thereon.

It is becoming more common for surgical equipment to contain tags that are conveniently readable by remote equipment. This has a number of benefits: it provides a simple means for accounting for items used in surgery, e.g. to track which patients they have been used upon, and to conveniently check whether a particular item has been, for example, accidentally left inside a patient. Radio Frequency Identification (RFID) tags are particularly convenient for such purposes, as they are small, and can be made to have individual identification numbers; some even have a rewritable memory, allowing data to be stored on them, such as the number of times the item has been used, or when it was last cleaned.

The cleaning done on surgical equipment is generally a very high temperature sterilisation procedure that takes place in an autoclave. Typically, several items are put onto a tray, and the tray put into the autoclave for cleaning and sterilisation, using a conveyor system. Due to the temperatures involved, a metal tray is used, as other materials (such as plastics) may not easily cope in such conditions. It is often desired to conduct an audit of the surgical equipment when it has been cleaned, and so the reading of the RFID tags is conveniently done whilst they are on the tray. However, it has been found that the metal tray can adversely affect the ability to read RFID tags on items upon it.

There is also a need in other areas to be able to read RFID tags from multiple items simultaneously, or substantially simultaneously. The items may be stored in packaging such as boxes, and sometimes multiple boxes.

-2 The boxes may interfere with the operation of the RFID tag reader and any associated tags in the vicinity.

It is an object of the present invention to overcome or ameliorate one or more problems with the prior art.

According to a first aspect of the invention there is provided a receptacle for holding objects, wherein the receptacle is made substantially or totally from metal or other electrically conductive material, and wherein the objects may typically contain devices receptive to energy emanated by an associated transceiver, within a defined frequency band, characterised in that a characteristic of the receptacle is adapted to promote the transfer of the emanated energy within the defined band between the objects and the associated transceiver, to promote communication therebetween.

By adapting the structure of the receptacle to promote energy transfer in a frequency band of interest, the receptacle improves the chances of an associated system being able to communicate with any devices receptive to such energy present on the receptacle, such as an RFID tag. The energy may be electromagnetic energy, as is emitted from an antenna, or may be a magnetic or electric field, as may be emanated by an inductor or a capacitor respectively.

The structure may promote the transfer of energy, including EM energy, in various ways.

Firstly, the receptacle may be arranged to be resonant within the defined frequency band. When irradiated by radio waves, any metal structure will support surface currents. By suitable design or modification, as described herein, the receptacle can be made to resonate within the defined frequency

-3band and hence the magnitude of the surface currents is maximised within this frequency band. The higher the current magnitude the greater the EM energy within the receptacle will be and hence the greater is the probability of communicating successfully with any proximate devices such as RFID tags.

Another approach to fostering the propagation of EM energy within the receptacle is to modify its structure such that it transmits a substantial proportion of incident EM energy through it, rather than reflecting it. This is accomplished in some embodiments of the invention by splitting a base of the receptacle into two parts and forming a cavity between them through which EM energy can propagate.

A further approach is to increase the separation between the metal of the receptacle and the (e.g.) RFID tag attached to objects within the receptacle to help facilitate more efficient communication with the RFID tags. For example, a dielectric liner may be used within the receptacle to provide such a separation.

In some embodiments the receptacle may conveniently be a tray, or similar item having a generally horizontal base upon which objects may be placed.

Some embodiments may comprise a receptacle having at least one of a slot, an aperture or a cavity formed therein, wherein said slot, aperture or cavity is arranged to have a resonant frequency within the defined frequency band. Such slots, cavities or apertures can conveniently re-radiate incident EM energy in directions dependent upon their properties, such as size and shape. The slot, cavity or aperture may have a resonant frequency (or multiple resonant frequencies) dependent upon the shape, size and location thereof. Thus, these parameters may be chosen to be compatible with the frequency or frequencies used by the RFID tags expected to be used with the receptacle.

-4Note that, except where context disallows it, one or more slots, cavities and/or apertures that have the purpose of propagating or redirecting EM energy may be collectively referred to herein as an aperture in the singular, and apertures in the plural.

Embodiments may have a plurality of apertures located thereon.

Some embodiments may have at least one aperture in the base of the receptacle, and some may have at least one aperture in the sidewall of the receptacle. The embodiment may have a lid or cover. For those embodiments that have such a lid or cover the embodiment may have at least one aperture in the lid or cover. Some embodiments of the invention may have at least one aperture that extends to or across an inside edge of the receptacle, such as between the base and a sidewall, between sidewalls, or between a sidewall and the lid or top.

Some embodiments may have one or more apertures that have an end that does not extend to an outside edge of the receptacle. Thus, in such embodiments, the aperture effectively forms a hole through the receptacle, and the aperture may be regarded as “closed”, or a “closed slot”. Instead or as well, some embodiments may have one or more apertures that intersect with an outside edge, such as at a top (when oriented in conventional use) part of a side wall of the receptacle, or the edge of a lid etc. Such apertures may be regarded as open apertures, or, as appropriate, open slots.

Some embodiments of the invention may comprise a receptacle wherein a base, side and/or top thereof comprises at least one element having a functionally three dimensional structure, the function of which is to resonate within the defined frequency band. Advantageously, a base, side, and/or top of the receptacle may comprise a plurality of such elements.

-5Some embodiments of the invention may comprise a receptacle having at least one slot, and wherein the slot has at least one sub-slot crossing said slot and running generally orthogonal thereto, wherein the sub-slot is shorter than the slot. The at least one sub-slot may be used to tune the frequency or the bandwidth of EM radiation at which the slot is resonant. By using a plurality of sub-slots of appropriate length and position, the resonant bandwidth may be increased. Such techniques are known to the normally skilled person. For example, the following references describe design and use of slot antennas:

G. Kumar, K.P. Kay “Broadband Microstrip Antennas,” Artech House, Inc., 685 Canton Street, Norwood, MA 02062, USA, 2003. (Particularly chapter 6).

K. Wong, “Compact and Broadband Microstrip Antennas,” John Wiley and sons, Inc., Third Avenue, New York, NY, 10158-0012, USA, 2002. (See in particular chapters 1 - 6).

The receptacles may conveniently, in some embodiments, have spacers located on an outside part thereof, that are arranged to provide a separation between adjacently stacked receptacles. The spacing provides a clearer path for energy traveling to or from a tag reader when multiple receptacles are used together, and so aids communication with tags that may be located further from the tag reader, potentially with one or more other receptacles in the communications path. The spacers may be, in some embodiments, detachable from the main body of the receptacle.

Advantageously, receptacles that may be stacked together may have slots that are co-operatively located on nearest-neighbour surfaces to encourage radiation to pass between them. Advantageously, the receptacles may have couplings that maintain adjacent receptacles in a defined arrangement. The

-6couplings may, in some embodiments, also function as the spacing elements mentioned above. The couplings or spacers may be made from a metallic or conductive material, or from a dielectric material.

The couplings or spacing elements may conveniently, in some embodiments, act as supports for the receptacles.

It is known that RFID tags often have antennas that are receptive in different ways to different polarisations of EM radiation. Thus, the physical orientation of the tag may change its ability to receive radiation of particular polarisations. It is therefore known to communicate with RFID tags and the like using antennas with multiple, e.g. vertical and horizontal, polarisations. Some embodiments of the invention may reflect this by providing apertures that are receptive to radiation of different polarisations.

An embodiment may, for example have a first slot and a second slot, wherein the first slot runs orthogonal to the second slot. In some embodiments, the first slot may intersect with the second slot. Other forms of aperture may also be arranged to have susceptibility to multiple polarisations, as is known to a normally skilled person, for example nonlinear slots or other apertures may be used..

Some embodiments of the invention may comprise a receptacle wherein a base, side, and/or top of the receptacle comprises at least two layers separated by an air gap across a substantial area of the base or sidewall. The two layers may be connected together, such as with an insulating material, or a conductive material, such as a metal.

The size, shape, and relative positions of the at least two layers may be chosen to provide a resonance within the defined frequency band. Such a structure constitutes a cavity, such as a sub-wavelength cavity or resonant cavity in proximity to the EM fields emitted by the transceiver, and therefore

-7any induced currents may be relatively high-valued and hence facilitate communication with any tags in the receptacle. The size of the gaps between the metal layers in the base, sidewall(s) or top may be chosen so as to facilitate efficient transmission of EM energy through the cavity (and hence through the receptacle) and/or alter the resonant frequency of the system.

It will be appreciated in relation to embodiments of the invention that, where an aperture is open, e.g. there is metal on two or even three sides but not four sides of a slot, then the aperture will generally allow propagation of energy even if the wavelength of the energy is significantly greater than the size of the aperture. If, however, the aperture is closed (e.g. having metal on all sides of a planar slot, such as a hole in a solid metal sheet), the energy propagation through the aperture will generally be inefficient, except where the energy has a frequency close to the resonant frequency of the aperture.

Some embodiments may have air (or other dielectric) gaps in the base and/or sidewalls of the receptacle whose purpose is to allow radiation to pass through the receptacle. This provides a greater probability that a tag may be successfully read when the transmit and receive antennas of an associated tag reader are positioned on opposing sides of a receptacle. For example, a transmit antenna may be mounted above a receptacle conveyor, with an associated receive antenna mounted below it.

In some embodiments a solid dielectric may be used within or alongside slots or other gaps in the receptacle, to provide, for example, additional strength, or to waterproof or otherwise seal it, or to prevent smaller items from falling out of the receptacle.

-8Some embodiments may have a form that increases the probability of a gap or spacing being present between a base or sidewall of the receptacle and a tag on an object within the receptacle. This is achieved, in some embodiments of the invention, by introducing undulations into one or more surfaces of the receptacle, such that the metal of the receptacle contacts with the objects therein only at a series of points rather than along the entirety of its length. The undulations may comprise variations in height, across a base of the receptacle. These undulations lower the probability that a tag attached to an object will be in contact with, or be very close to the metal surface of the receptacle. Thus, there is more chance of an air gap being present between the tag and the metallic surface of the receptacle. A larger air gap will decrease the extent to which the metal of the tray shields and de-tunes the tag, thus increasing the probability of the tag being successfully read. The characteristics of the undulations, e.g. the size (depth, width, length), shape and quantity may be chosen by trial and error, or by modelling (using e.g. EM modelling software) the performance of various candidate forms.

The defined frequency band of the tags being used may be taken into consideration during the design of the undulations. As a starting point, a peak-to-trough distance of the undulations of around 20mm may be used for tags operating in the 800MHz - 1000MHz range, although it will be appreciated that smaller undulations will still be beneficial so long as they provide a degree of separation between the tag and the receptacle base.

The receptacle may additionally have one or more perforations or slits or other apertures, as described above, which may encourage coupling of EM energy within the defined band using the principles described above.

In some embodiments of the invention the surface having the array of undulations comprises an additional formed layer, that is arranged to sit against a second, structural layer. The formed layer may comprise a

-9metallic layer, and may itself be a structural element. The formed layer may be a removable insert.

Some embodiments of the invention may have an insert, such as a dielectric insert, that is arranged to prevent articles from lying flat against a conductive surface of the receptacle. Such an insert may be arranged to sit on a base of the receptacle. The insert may be shaped to provide e.g. a varying height across the base, or may be generally planar.

Some embodiments of the invention may have part or all of a surface such as a wall of the receptacle, that comprises of a series of posts or the like, where the posts are arranged to have a resonance at a frequency within the defined band, or which allow EM radiation to pass between the posts. For example, each post may comprise of a metallic loop, or be substantially linear. The plurality of posts may be located close enough in proximity to provide an effective barrier or wall preventing items stored within the receptacle from falling out. Such embodiments may optionally therefore use dielectric material to “fill in the gaps”, where those gaps are otherwise large enough to allow the intended contents of the receptacle to fall from the receptacle.

Embodiments of the invention may be made from a metal sheet or sheets. The metal is advantageously stainless steel, which is strong and able to cope with repeated high temperature cleaning without degeneration. Alternatively, the receptacle may be made at least partially from a metal gauze or mesh The metal may be stainless steel, or may be any other suitable metal.

A slot may generally be linear in nature, or, alternatively, may have a curve or curves, so forming a serpentine slot. Embodiments having such a slot may have improved cross- or dual-polarisation performance. Also, a curved

- 10or meander may be used to increase the inductance of a slot in a small footprint, which may be used to tune the resonant frequency of a slot.

Embodiments of the invention will now be described in more detail, by way of example only, with reference to the following figures, of which:

Figure 1 diagrammatically illustrates a (prior art) tray, as may be used to hold articles passing through a sterilisation system such as an autoclave;

Figure 2 diagrammatically illustrates various embodiments of the invention, all having one or more slots that extend to an outer edge of the tray;

Figure 3 diagrammatically illustrates an embodiment wherein a slot does not extend to an outer edge of the tray;

Figure 4 diagrammatically illustrates an embodiment wherein a two-layer base is used to produce a half-wave resonator;

Figure 5 diagrammatically illustrates an embodiment wherein a base of a tray comprises a plurality of quarter-wave resonators;

Figures 6 diagrammatically illustrates two embodiments showing a tray having an undulating base;

Figure 7 diagrammatically illustrates an embodiments of the invention comprising a box with spacing elements; and

Figure 8 diagrammatically illustrates two more embodiments of the invention.

-11 Figure 1 shows a tray 1 having a base 2 and sidewalls 3, and having a general form of the type in current usage in hospitals for the sterilisation of surgical instruments. The tray is typically made from stainless steel or aluminium, so as to withstand the environment in an autoclave. It is increasingly common for the surgical instruments that are the targets of the sterilisation process in the autoclave to have RFID tags affixed to them in some manner. This allows individual instruments to be tracked, both to know whether the instrument has been subject to sterilisation, and also to monitor their usage history. An RFID reader is often placed alongside the autoclave, allowing it to monitor the instruments as they enter or leave it. RFID readers work by generating a magnetic, electric, or an electromagnetic field, which couples into any RFID tags in the vicinity. The RFID tag, using power from this energy coupling, then generates its own field, or modulates the existing field in a manner that uniquely identifies it. The energy generated or modulated by the tag is picked up by the tag reader, effectively reading the data generated by the tag.

The metal trays - by their nature highly electrically conductive - frequently act to disrupt the energy fields generated by the reader, and also alter the behaviour of tags in close proximity thereto- most notably the operating or resonant frequencies of their antennas . This can lead to weakened fields close to the tray, which is just where the instruments, and their tags, tend to lie. Thus, the tag reader tends to fail to read some of the tags present in the tray.

Embodiments of the invention provide a means to reduce disruption to the energy field present in the tray, where the tags reside. Figure 2 illustrates a series of such embodiments, each incorporating one or more open slots.

Figure 2a shows a tray 200 with a slot 201 formed therein, where the slot runs from an outside edge down a side 202 and along a base 203 of the tray towards a central region thereof. The length and width of the slot are

- 12 chosen, using well known design principles, so as to be resonant at a frequency used by an associated RFID tag reader and RFID tags applied to articles, such as surgical instruments, that will be carried by the tray. When illuminated with an EM field at an appropriate frequency, the resonance increases the surface currents and, consequently, the field strength close to the surface of the tray. This increases the chances of successful communication between the tag reader and the tag itself. The slot length chosen will typically be close to a multiple of a quarter of the wavelength of the illuminating radiation for the open slot 201.

The tray 200 (for this, and for other embodiments) may be any suitable size, based upon the size and quantity of objects it is expected to hold during a sterilisation process. Typically the size will be around 300m - 600mm on each side, although clearly the invention is applicable to trays and other receptacles outside of these dimensions.

Figures 2b-2e show trays having further variations of slot types that have particular beneficial effects. Figure 2b shows a tray having a “T” slot, that has improved cross and dual polar performance (as compared to the embodiments of Fig. 2a), and allows, by selection of the dimensions of the horizontal bar 204 of the T, a degree of tuning of the resonant bandwidth. Similarly, the embodiment of Figure 2c shows a tray with a cross slot, where selection of the dimensions of the transverse slot 205 again provides improved cross and dual polar performance. Figure 2d shows a linear slot with transverse loading sub-slots 206 for frequency tuning. Figure 2e shows a tray having a pair of slots 207 that run along the edges of the base of the tray, on adjoining sides. Each slot acts as a resonant cavity in orthogonal polarisations. Each slot 207 extends up to the top of a sidewall 208 of the tray, and is an external resonant slot. Similarly, the other embodiments shown in Figure 2 also have slots that extend up their respective sidewalls, to become external resonant slots.

- 13For those slots e.g. 205 that are closed slots (i.e. the slots ends are shorted out) the slot length will typically be chosen to be close to a multiple of a half of the wavelength of the illuminating radiation.

Figure 3 shows an embodiment of the invention comprising a tray 300 having an internal resonant slot 301 in the form of a cross, with each arm of the cross having transverse loading sub-slots 302. The use of an internal resonant slot allows the sides of the tray to maintain their mechanical integrity, and so provide for a stronger tray. The symmetric cross slot 301 also provides for good dual-polarisation performance, and thus enhances read performance of tags in random orientations. The length of the slot 301 is typically close to a half wavelength multiple, as explained above.

Figure 4 shows an embodiment of the invention comprising a tray 400 having a base in a two-part split form. Figure 4a shows a regular perspective view of the tray, whilst Figure 4b has the same view, but with the upper tray shown partially transparent, to provide a view of the spacer.

A first element 401 comprises a lower base 402 with a first pair of adjacent sides 403, while a second element comprises an upper base 404 with a second pair of adjacent sides 405. The lower base 402 and upper base 404 are separated by a spacer 406. The purpose of the spacer 406 is to provide a gap, between the lower and upper bases, that acts as a resonant cavity. Thus the gap will comprise, in this embodiment, an air gap, although other embodiments may incorporate a gap that is largely or totally filled with another dielectric material. This enhances the EM field in the vicinity of the tray. The embodiment also permits energy to pass through the receptacle, and so improves the chances of an RFID tag present in the tray being successfully read by a tag reader.

- 14The spacer may be a dielectric material, or may alternatively comprise a metallic or otherwise conductive post, used to maintain the gap (and hence the resonant properties) between. The normally skilled person will realise the design implications, in terms of having the lower base electrically insulated from the upper base, or instead having one or more conductive spacers to hold the lower and upper base apart. The effects of the quantity, position and base separation upon the resonant properties of the cavity formed between the bases can, for example, be modelled using standard EM modelling software, or otherwise calculated. Typically, the degree of overlap between the lower 402 and upper 404 bases may be arranged to be approximately a multiple of half a wavelength long.

Figure 5 shows a further embodiment of the present invention. Here, as shown in Figure 5a, a tray 500 comprises of a base 501 and sides 502. The base is made up from an array of individual resonators 503 mounted (e.g. by welding) to either a side 502 or one of two support bars 504. The individual resonators making up the base 501 are positioned in a tight formation, with relatively small air gaps between each, so that the base will not allow typical sized surgical instruments to either fall out through gaps between adjacent radiators, or get caught in such gaps. Alternatively, some embodiments may have a dielectric material such as ceramic (e.g. Alumina) or polymer (e.g. Polypropylene) either filling in the gaps, or providing a uniform covering across an upper surface of the resonators. A liner, to space objects away from the base, may also be employed in this, or other embodiments.

A single resonator 510 is shown in more detail in Figure 5b. It comprises of a pair of metal plates 511, 512, that are joined at one end by a metal spacer 513, to create a “tuning fork” style resonator. For operation at a wavelength of around 300mm in air, the resonator will typically be around 75mm in length, but the design of such a resonator, including the selection of the

- 15various dimensions to achieve a particular resonant frequency, will be understood by a person of ordinary skill in the art of electromagnetic resonators.

Two further embodiments of the invention are shown in Figures 6a and 6b. Figure 6a shows a tray 600 comprising a base 601 and sidewalls 602. The base 601 is made from metal sheet that has been pressed to create a series of undulations. The size of the undulations may be chosen dependent upon the size of articles to be placed in the tray, but typically a pitch between adjacent peaks may be around 2cm to 5cm, whereas the depth of the undulations, from a peak to a lowest point of a trough may be typically between 0.5cm and 2cm, but other dimensions may clearly be used as appropriate. The undulations therefore comprise an array of peaks 603 and troughs 604, and present a rough surface for articles to sit upon, and so, when an article such as a surgical instrument is placed on the tray there is an increased probability that an RFID tag on the article will be not directly adjacent the metal base (as compared to a tray having a flat base). This increases the probability of the tag being successfully read by an associated tag reader.

Of course, there are likely to be times when articles placed on the base 601 end up oriented such that a tag thereon is directly adjacent the metal of the base - most likely at a peak of the undulating surface. Figure 6b shows an embodiment that improves the chances or successfully reading a tag in such a position. It shows a tray 610 having a base 611 and sidewalls 615. The base 611 has undulations pressed therein, in similar fashion to that shown in Figure 6a, to provide a series of peaks 612 and troughs 613. However, it differs in that the peaks 612 of each undulation have a slot 614 formed therein. The slots 614 are adapted to be resonant, at or near the frequency band used by tags attached to articles to be carried by the tray. The slots therefore improve the chances of a tag that is sitting adjacent the metal base at a peak, or in the vicinity of a peak, being successfully read by

- 16an associated tag reader. It will be appreciated that, although Figure 6b shows a simple slot present in each peak, other types of slot may be used as well as, or instead of the simple slot shown. For example, some slots may run along an orthogonal axis to others, or a cross, or other slot form may be used. Slot dimensions may for example be chosen according to the guidelines presented above.

Figure 7 shows an embodiment of the invention comprising a metal box 700 with a lid 701. The box 700 has slots e.g. 702 located in each side, and in the base, and the lid has a similar slot arrangement 703. Of course, it will be appreciated that the particular slot arrangement shown is not the only one that can be used, and other arrangements, or alternatives to slots, such as those shown in the above embodiments, may equally well be applied, as they all promote the transmission of EM energy of particular frequencies through the box material.

Spacers 704 are mounted on each lower corner of the box. These are arranged to loosely couple mechanically to adjacent boxes when stacked together, and also to hold each box separated from its immediate neighbours. This promotes the transmission of EM energy into the boxes, and hence to any RFID tags that may be present therein, and also around the boxes so that items in a series of stacked boxes can also be read, without a box unduly blocking radiation from objects in other boxes.

Figure 8a shows embodiment broadly similar to that of Figure 7 wherein spacers are used to hold neighbouring receptacles separated, thus allowing better transference of EM energy into and around the receptacles when a plurality are stacked together. Receptacles, e.g. 800 each have a series of spacers e.g. 801 located thereon at or near at least some of their corners, that act to buffer against, and provide a known separation distance, between their neighbours, both horizontally and vertically. The spacers may conveniently be detachable from the receptacles, so that the spacers do not

- 17hinder use of the receptacle when it is not holding RFID tagged items, or if it is being used for purposes that do not require bulk reading of such tags.

The separation distance may be chosen to allow EM energy to pass between adjacent receptacles, given prior knowledge of the wavelength employed by an associated tag reader.

Note that the receptacles are shown, for convenience of illustration, without any slots or the like, but in practice the receptacles will have a characteristic, such as one or more slots or other resonant features, e.g. as shown in other embodiments, that promotes EM transfer.

Figure 8b shows a further embodiment of the present invention. A receptacle, comprising a tray 810, has a base 811 and sidewalls that comprise of a series of electrically conductive posts e.g. 812. Between each post is a dielectric (air or a solid), and this arrangement acts to disrupt the boundary conditions as seen by an EM wavefront, as compared to a solid conducting wall. This therefore reduces any blocking effect that a solid wall would otherwise have upon the EM wavefront, thus improving the likelihood of an RFID tag within the receptacle being read by a reader.

Note that the embodiments described above have utility with differing types of RFID tag, including those that use EM fields, and those that use near-field techniques such as inductive or capacitive coupling.

Although the embodiments are shown as being formed from sheet material, typically metal, it will be appreciated that a gauze can also be used. Preferably, the gauze would have an aperture size that is electrically small compared to the wavelength used by associated tags and tag readers.

It will be appreciated that the embodiments described above illustrate the invention but are not to be regarded as restricting the invention. Other modifications or variations to the embodiments shown will be apparent to

- 18the skilled person but will still be in accordance with the present invention. For example, it will be readily apparent that, where appropriate (given mechanical and electrical considerations) combinations of elements of the various embodiments shown, and similar such elements, can be brought together in a single embodiment.

Claims

1. A receptacle for holding objects, wherein the receptacle is made substantially or totally from metal or other electrically conductive material, and wherein the objects may typically contain devices receptive to energy emanated by an associated transceiver, within a defined frequency band, characterised in that a characteristic of the receptacle is adapted to promote the transfer of the emanated energy within the defined band between the objects and the associated transceiver, to promote communication therebetween.

2. A receptacle as claimed in claim 1 wherein the adaption to the characteristic of the receptacle comprises at least one of a slot, an aperture or a cavity formed therein, wherein said slot, aperture or cavity is arranged to have a resonant frequency within the defined frequency band.

3. A receptacle as claimed in any of the above claims wherein at least one of said slots, cavities or apertures extends to or across an inside edge of the receptacle.

4. A receptacle as claimed in claim 2 wherein at least one of said slots, apertures or cavities has an end that does not extend to an outside edge of the receptacle, so comprising a closed slot.

5 A receptacle as claimed in claim 2 or claim 3 wherein at least one of said slots, apertures or cavities has an end that extends to an outside edge of the receptacle, so comprising an open slot.

6. A receptacle as claimed in any of the above claims wherein the receptacle comprises at least one slot, and wherein the slot has at least one sub-slot crossing said slot, wherein the sub-slot is shorter than the slot.

-207. A receptacle as claimed in any of the above claims wherein the receptacle has at least a first and a second slot, the first slot running orthogonal to the second slot.

8. A receptacle as claimed in claim 7 wherein the first slot intersects with the second slot.

9. A receptacle as claimed in any of the above claims wherein a base, sidewall or top of the receptacle comprises at least one element having a functionally three dimensional structure.

10. A receptacle as claimed in any of the above claims wherein a base, sidewall or top of the receptacle has an array of undulations formed therein, that generally prevent articles from lying flat against the said base sidewall or top.

11. A receptacle as claimed in claim 10 wherein the undulations comprise an array of peaks and troughs.

12. A receptacle as claimed in claim 11 when dependent upon claim 2, wherein at least one slot, aperture or cavity is formed at or near a peak of an undulation.

13. A receptacle as claimed in any of claims 10 to 12 wherein the surface having the array of undulations comprises an additional formed layer, that is arranged to sit against a second, structural layer.

14. A receptacle as claimed in any of the above claims further comprising a dielectric insert arranged to prevent articles from lying flat against a conductive surface of the receptacle.

-21

15. A receptacle as claimed in any of the above claims wherein a base, sidewall or top of the receptacle comprises at least two layers separated by an air gap across a substantial area of said base, sidewall or top.

16. A receptacle as claimed in any of the above claims wherein the receptacle is made from metal sheet.

17. A receptacle as claimed in any of claims 1 to 15 wherein the receptacle is made from a gauze, mesh, or perforated metal sheet.

18. A receptacle as claimed in any of the above claims wherein the at least one slot has a dielectric material located proximate thereto that acts to prevent objects passing through the slot.

19. A receptacle as claimed in any of the above claims wherein the receptacle further comprises at least one coupling element, for constraining the position of the receptacle with respect to a neighbouring receptacle.

20. A receptacle as claimed in claim 19 wherein the coupling element further acts to provide a spacing between adjacent receptacles, where the spacing provides a path for EM radiation.

21. A receptacle as claimed in any of the above claims wherein a slot formed therein is arranged, when stacked adjacent to another receptacle to co-operate with a slot in the adjacent receptacle, to facilitate the passage of EM radiation therethrough.

22. A receptacle as claimed in any of the above claims wherein the receptacle is a tray, box, rack, or the like.

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23. A receptacle substantially as hereinbefore described, with reference to any of Figures 2 to 7.

Intellectual

Property

Office

GB1608831.2

1-23