TITLE OF THE INVENTION

Portal Antenna BACKGROUND TO THE INVENTION

This invention relates to an antenna and, more particularly, an antenna that can be used to enable low frequency RFID devices carried by animals to be read particularly when the animals are proceeding through a race or the like.

The use of low frequency RFID devices to provide a means of identification of animals is well known. The RFID device is interrogated (read) by a suitable reader that incorporates an antenna.

There are many situations in which such devices need to be read. One is in a stock race through which animals will move.

As with any identification system there is a need to maintain a high level of integrity so as to, for example, ensure that each tagged animal moving through a stock race will have its RFID device read. A problem that can arise in such situations is that the animal may move through too quickly for the RFID device to be read, or can move through the race in such a manner that the RFID device is not detected and read. This is especially so with small animals, such as sheep, where the animals can move rapidly through a race and, furthermore, can move in an unpredictable manner. The latter can result in a RFlD device not being read due to the animal moving through a null zone in the antenna.

A solution to this problem is to ensure that animals moving through the race are held at some point in the race so that the RFID device can be read whereupon the animal is then allowed to move through the race. This, however, can be difficult for a variety of reasons but, in any event, does result in the procedure of moving the animals through the race and

the reading of the RFID devices to be a more time consuming and tedious process than is desired.

SUMMARY OF THE INVENTION

There is, therefore, a need for an antenna that can be placed in the stock race to effectively and efficiently read low frequency RFID devices carried by animals as the animals move through the race. An object of the present invention is to provide such an antenna or, at least, provide the public with a useful choice.

Broadly according to one aspect of the present invention there is provide a portal antenna including a portal structure defining an area through which an animal can pass and at least one coil of antenna conductor wound around the portal structure to extend around the area through which an animal can pass.

In a preferred form of the invention there is at least one elongate radiator element which projects either side of the portal structure and has a longitudinal axis that is at an angle of less than 90° to a plane transverse to the direction in which an animal passes through the portal structure.

In a preferred form the radiator(s) are of metal. They can form a separate structure or be part of the wall structure of a stock race.

According to one preferred form, the radiators are at substantially 30° to the coil(s).

In one form of the invention there are two coils, one located adjacent each edge of the portal structure, said coils being coupled together.

A connector unit carried by the portal structure is in one form connected to the coil(s).

According to a preferred form, the lower end of the portal structure has a floor from which projects at an incline a pair of opposed walls which connect to substantially vertically disposed walls of the portal structure.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following more detailed description of the invention according to one preferred embodiment:-

Figure 1 is a front elevation view of a portal antenna according to the present invention in one preferred embodiment,

Figure 2 is a side elevation view of the antenna as shown in Figure 1 ,

Figure 3 is a perspective view of the antenna of Figures 1 and 2 showing the winding of a first coil of antenna wire on the portal structure,

Figure 4 is a view similar to Figure 3 but showing completion of the winding of the antenna onto the portal structure to form a second coil,

Figure 5 is a perspective illustration of the antenna in a stock race,

Figure 6 is a side elevation view of a second embodiment of the invention illustrating the windings on the portal structure,

Figure 7 is a front elevation view of the antenna as shown in Figure 6,

Figure 8 is an illustration of a framework with diagonal pipe sections into which the portal antenna structure as shown in Figures 6 and 7 can be mounted,

Figure 9 is a view similar to Figure 8 but showing a structure intended for use with the antenna as illustrated in Figures 1 to 4,

Figure 10 is a perspective view of the portal structure of a third embodiment showing the layout of grooves incorporated therein and in which wires or conductors are located to form the antenna,

Figure 1 1 is a face view of one sidewall of the portal structure of Figure 10,

Figure 12 is a face view of the other and opposite sidewall of the portal structure of Figure 10, and

Figure 13 is a detail view of a groove in which antenna conductor elements reside according to one embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Two embodiments of the portal antenna according to the present invention are described herein and shown in Figures 1 to 4 and Figures 6 to 7 of the drawings. In Figures 10 to 1 2 there is shown a third embodiment in which a different layout of wires/conductors is provided by way of grooves formed in the portal structure.

The first embodiment, with reference to Figures 1 -5 is what can be described as an inclined portal with horizontal radiators while the second embodiment, as shown more particularly in Figures 6 and 7, is a vertically disposed portal with diagonal radiators.

Referring firstly to Figures 1 -4, the portal antenna 10 is based on a portal structure 1 1 formed from plastic, timber or any non-metallic material. In the preferred form of the invention the portal structure 1 1 , when looking end on (i.e. Figure 1 ), includes a pair of parallel sidewalls 1 2 each of which merges into inclined wall 13. The inclined walls 1 3 converge to a cross-wall 14 at the bottom of the portal structure 1 1. A top wall 1 5 extends between the upper extremities of the sidewalls 12.

In the first form of the invention, the portal structure 1 1 extends upwardly away from the bottom wall or floor 14 at an angle of about 60° as can be seen in Figure 2. In use, the floor or bottom wall 14 will be approximately horizontal or, at least, parallel to the floor of the stock race in which the portal antenna is, in use, located.

Into the portal structure 1 1 (e.g. by way of grooves formed therein) an antenna wire is wound. As shown in Figure 3 the antenna wire is wound in multiple turns adjacent one end of the portal structure 1 1. These multiple turns of the conductor 1 7 form a loop 1 8. Loop 18 runs parallel to the edge of the portal structure 1 1 so that an animal will pass through the loop 1 8 as it enters the portal structure.

The wire or conductor 1 7 is then laid over to the other edge of the portal structure 1 1 where a second loop 19 is wound. This second loop 19 is located adjacent the edge where the animal will exit the structure, assuming that the direction of movement of the animal is as shown in Figures 3 and 4. Consequently, an animal passing through the portal antenna 10 will pass through two loops 1 8 and 1 9 formed from a single conductor 1 7.

The start of the conductor 17 and the end of the conductor terminates at an electrical connector 20 (e.g. mounted by top wall 1 1 ) to allow circuit connection to the control electronics of the reader for the RFID devices. The control electronics of the reader, as

indeed the reader itself, does not form part of the invention and hence is not described herein.

The second coil or loop 1 9 is wound in an opposite direction to the first coil loop 1 8. The loops 1 8 and 1 9 are, therefore, out of phase.

Once the loops 1 8 and 19 have been wound onto the portal structure a suitable protective covering 32 (see Fig. 1 3) can be applied thereover. This covering can be in the form a plastic welded bead, an epoxy mixture, or any other non-conductive, waterproof seal.

In Figure 3 there is shown, by way of arrows, the direction of travel of an animal though the portal antenna. However, the antenna can be used bi-directionally. Therefore, the animal may travel in the opposite direction if such is the direction of movement of the animals through the race in which the portal antenna is located.

In a preferred embodiment the portal antenna 1 0 is located between a plurality of elongate radiators in the form of ferrous/magnetically conductive metal pipes 21 of about 1 metre in length. These pipes 21 extend horizontally or in other words substantially parallel to the direction of travel of an animal through the antenna structure. These pipes 21 act as radiators to extend the antenna read field.

Therefore, according to this preferred form of the invention the radiators 21 are nominally horizontal while the portal structure 1 1 lies at an angle of around 60° to the radiators. More particularly, the coils 1 8 and 1 9 are at an angle of substantially 60" to the radiators.

The intention with such a design is that if a null zone is formed in the centre zone of the antenna it (the null zone) will be on an opposing angle of substantially 60°. This means that

it will be almost impossible for an animal to move through the antenna and follow the null zone.

A further role of the radiators is to distort the electromagnetic field created by the antenna so that the field couples in a more optimal manner with the RFID devices carried by the animals.

The horizontal pipe sections 21 can be formed by the pipe work of a skeletal frame forming the sides of the race as shown in Figure 5. The effective length of the radiators will be determined by a vertical pipe or metal strap located either side of the portal antenna so that the effective length of the pipe sections forming the radiators will be approximately 1000mm as previously described.

It is believed that it is desirable that the length of the radiators be in the order of 1000mm in length because increasing the dimension of the radiators will diminish the performance by introducing multiple RFID devices into the "read zone" of the portal antenna.

Figure 9 shows a frame comprising the horizontal pipes or radiators 21 with vertical end pipes 22. The resultant opposing side frames 23 are spaced apart by cross members 24 which as shown can be at the upper end of the sides but equally cross members can also be provided at the lower end of the side frames. It is envisaged that such an arrangement could be incorporated into a stock race by forming parts of the sides of the race or in the event of say, a timber race, the metal frame can be located therewithin.

The arrangement shown in Figure 9 illustrates a further form of the invention where additional radiator bars or pipes 21 ' are located over the top of the portal antenna thereby including coverage above the head of the animal. These additional radiators 21 ' are located between curved upper extensions 22' of the vertical pipes 22.

Turning now to Figures 6 and 7 there is shown an alternative embodiment of the portal antenna. According to this arrangement the portal structure I T is of a largely vertical orientation and is intended for use with radiator bars that are diagonal to the vertical orientation of the portal structure 1 1 '.

As with the first described embodiment the antenna conductor is wound onto the portal structure with multi turns of the conductor to form loops adjacent each edge of the structure. Thus, as with the first described embodiment, an animal passing through the structure will pass through a loop upon entry and a second loop upon exit.

In the preferred form of the invention, according to this embodiment, the radiators are once again metal pipe sections of about 1000mm in length but unlike the first embodiment these pipe sections extend in a direction about 60° to the horizontal. Once again, these angled radiator bars in conjunction with the largely vertical portal structure, will ensure that if a null zone is formed in the centre zone of the antenna, the null zone will be distorted at an angle close to 60°. Consequently, it will be almost impossible for an animal to move through the antenna and follow the null zone.

Referring to Figure 8 there is shown an arrangement similar to Figure 9 but with the radiators located at the aforementioned 60° angle.

The invention is open to modification as will be apparent to those skilled in the art. Variations to the embodiments disclosed herein can include the use of a single portal coil or more than two coils. A further possible modification is changing the shape of the portal structure 1 1 so that it forms a dome or a substantially "A" section at the top. In a further variation the relative angle between the portal structure and the radiators can differ from that described herein.

As disclosed above the conductor 1 7 is preferably wound into the portal structure 1 1 this being achieved by way of, for example, grooves formed in the walls and top and bottom of the portal structure. The groove can be of any suitable cross-section shape such as u- shape, which is preferred, but can be a shallow V-shape, curved shape or some other form of angular cross-section.

In the first and second embodiments described herein, the coils 1 8 and 19 are wound so as to be substantially parallel to the edges of the portal structure. This is shown, for example, in Figure 4 and 6. However, in Figures 10-1 2 a different layout of grooves is formed for the purpose of distorting the shape of the generated electromagnetic field to gain better coupling to the device on the animal.

As is illustrated in Figure 10 the top wall 1 5 and bottom wall 14, as well as one of the inclined walls 13, are provided with grooves 25 whereby the conductor will extend parallel to the edge of the walls. The other of the inclined walls 1 3 has the grooves diverging from an upper end down to the bottom wall 14. As shown in Figure 10 a more complex shaping of the grooves 25 are formed with Figures 1 1 and 12 showing face views of the sidewalls 1 2 to more fully define the shape of the grooves 25.

The side wall 12a of Figure 10 has grooves 25 that have lengths 26a and 26b that converge downwardly from the top edge of the sidewall 12a. One groove 25 then inclines along length 27 away from the other groove 25 to form a continuous straight line to the bottom edge of the sidewall 12a. The other groove 25 similarly inclines away along length 28 downwardly but at its lower end is formed so as to extend along length 29 which is substantially parallel to the side edge of the sidewall 12a.

With the sidewall 1 2b the grooves 25, once again, converge along lengths 30a and 30b inwardly from the top edge and then diverge downwardly via lengths 31 a and 31 b toward the lower end of the sidewall 12b. The points at which each of the grooves 25 changes from being convergent to divergent are at different distances from the top edge as is shown in Figure 12. This is similar to the arrangement in Figure 1 1 where the point at which the convergent grooves 25 change to divergent is at a different point from the top of the side wall 12a.

The purpose of this complex layout of the grooves 25 in sidewalls 12a and 12b is to distort the generated electromagnetic field to achieve a complex field pattern that allows better electrical coupling between the field and the conductors in the radio frequency device carried by the animal. Additionally, this field distortion causes the null zone to be minimised greatly. This embodiment is highly effective for race reading particularly when radiator bars described in the earlier embodiments are not present.

A further difference between the portal antenna using the structure in Figures 10-1 2 is that the coils 1 8 and 19 are wound "in phase". This means that the coil 1 8 is wound in the same direction as the coil 19.

The present invention, therefore, provides a portal antenna that forms a tunnel which can be placed in a stock race. The tunnel can be used bi-directionally. Animals tagged with low frequency RFID devices can be moved through the antenna in order to read the RFID devices.