Tereszczak, Mark (Putham Farm, Wheddon Cross Minehead, Somerset TA24 7AS, GB)
Webber, Richard (Putham Farm, Wheddon Cross Minehead, Somerset TA24 7AS, GB)
Tereszczak, Mark (Putham Farm, Wheddon Cross Minehead, Somerset TA24 7AS, GB)
| 1. | An antenna system for use in the identification of animals carrying coded electromagnetic signal emitting identifiers in a detection zone, the antenna arrangement comprising first and second antenna loops for positioning adjacent the detection zone, the first loop being a side loop disposed at a first side of the detection zone, and the second antenna loop straddling the detection zone and having first and second transversely opposed wing portions, the first wing portion being on the first side of the detection zone adjacent the side loop, the second wing portion being disposed on a second side of the detection zone, opposed to the first across an axis thereof, and traversing portions connecting the first and second wing portions and extending between the first and second sides of the detection zone. |
| 2. | A system according to claim 1 in which the side loop and the first wing portion overlap. |
| 3. | A system according to claim 1 or claim 2 in which the traversing portions of the second antenna loop traverse above or below the detection zone. |
| 4. | Antenna system according to any one of the preceding claims in which comprise a support structure on or in which the first and second antenna loops are supported in the specified disposition. |
| 5. | A system according to claim 4 incorporated in a passageway for livestock, having upright side structures corresponding to the first and second sides of the detection zone and supporting the antenna loops correspondingly. |
| 6. | A system according to claim 4 or 5 in which the antenna loops are incorporated in a restraint cage comprising restraining walls, at least one end opening, and restraint means for restraining an animal from leaving via the end opening. |
| 7. | A system according to any one of claims 1 to 5 in which the antenna system is mounted on or adjacent the entry or exit structure of a transporter for animals. |
| 8. | A system according to any one of the preceding claims, further comprising means for providing an AC power source with which the loops of the antenna form a series resonant circuit or circuits. |
| 9. | A system according to any one of the preceding claims comprising a tuning module to which the antennae are connected by coaxial cable. |
| 10. | A method of identifying one or more animals carrying respective coded electromagnetic emitters, by positioning the animal (s) in the detection zone of a system as defined in any one of claims 1 to 9 and using the antennae thereof to trigger and/or detect the coded emissions. |
| 11. | A method according to claim 10 which identifies cattle, sheep or pigs. |
| 12. | A method according to claim 10 or 11 in which the animals pass sequentially through a restricted passageway having side walls where the antenna system is provided. |
| 13. | A method according to any one of claims 10 to 12 in which the electromagnetic emitters are transponders, carried by the animals in ear tags, stomach boluses or subcutaneous implants. |
| 14. | A method according to any one of claims 10 to 13 comprising recording the animals'identities in an electronic database, optionally in conjunction with further data relating to one or more events or operations associated with the respective animals'presence in the detection zone. |
FIELD OF THE INVENTION This invention has to do with methods and apparatus for identifying and/or detecting animals, particularly but not exclusively cattle, sheep or pigs.
BACKGROUND It is known for animals to be equipped with electromagnetic identifiers which can interact with a detection system to indicate the presence of the identified animal near the detector. Various kinds of identifiers are known. A popular kind, because it avoids the need for any built-in power source, is a 'transponder'containing an inductive microcircuit which can be energized by the electromagnetic field of a suitable antenna so as to emit a characteristic electromagnetic identification signal for detection, e. g. by the same or another antenna. The idea behind these systems is the same: the antenna creates an electromagnetic field over a certain region.
Transponders containing microchips are energised when their circuits lie across (i. e. at an angle to) field lines of the electromagnetic field. Energising the transponder causes it to emit a response signal. The same or another antenna can detect the response signal and identify the transponder which has entered the antenna zone. Animals such as cattle are given electromagnetic identifiers, usually transponders, in ear
tags or in stomach boluses or under-skin implants, and these are energised/detected by an antenna mounted on the side of narrow passageways (races) through which they are herded. Animals passing the detection zone e. g. at a cattle market or slaughterhouse can be uniquely identified. Detected data can be fed to and logged on to a suitable control processor, either fixed or portable.
Other locations are also possible, e. g. in stalls or milking parlours.
PRIOR ART There have been numerous previous proposals of antenna arrangements for detecting electromagnetic or RFID identifiers on animals, e. g. in tags. A standard means is to mount a loop antenna on or in the side wall of a race such that the plane of the loop is parallel to the race. The antenna is set up as a series resonant circuit; when current flows through the antenna, an electromagnetic field is set up whose field lines extend around the edges of the antenna giving a toroidal shape.
As the loop is mounted on the side wall of the race, the field lines extend generally across the race as shown in Fig. 10. When a microchip in a transponder cuts those field lines (i. e. lies across or move through them), a current is induced in it, i. e. it is energised. See e. g.
WO 98/08182 which describes various refinements of such systems.
An alternative way is to have the plane of the loop perpendicular to the direction of a race or other animal path so that the animals walk through it: this is known
as a portal antenna. In this arrangement the field lines extend in the direction of the path.
It is important that no animals are missed. The simple known systems described above have a significant chance that the transponder will not be energised because the microchip will be at the wrong angle. If the microchip is parallel to the field lines, i. e. does not cut lines of different electromagnetic strength, it will not be energised. This is more of a problem with ear tags than with boluses and implants, because the ear tags move around a lot when the animals move their heads. The advent of stricter controls on livestock movements, particularly following the BSE and foot and mouth outbreaks, means that it is now vital that all the animals are identified. If one is missed, then all must be passed through again because there is no way of telling which animal was missed.
A number of proposals have been made for antennae which will detect transponders at various orientations.
GB 1599120 shows two loop antennae with their planes perpendicular to one another. Each loop produces its own field, nominally perpendicular although each field will affect the other due to mutual inductance, causing significant'dead zones'.
US 4679046 shows one loop twisted as a figure of eight and surrounded by a simple loop, the two being coplanar. This aims for the same effect as two perpendicular loops, but with a planar installation.
However it still suffers from dead zones'due to mutual
inductance between the loops. US 4679046 discloses two ways of alleviating dead zones'. The first way is to multiplex the two loops. Multiplexing involves powering single loops of the set in turn over a short cycle, so that the net effect over time is a field in both directions. This solves the problem of mutual inductance, but adds further problems in terms of the complexity of the system circuit and lost'time as explained below. The second way is to introduce a phase shift between the currents in each loop to create a circularly polarised field. The latter arrangement is complicated because finding the correct phase shift can be difficult, and the phase shift circuit requires more components and expense. Moreover because US 4679046 uses two antennae to provide a field which still acts substantially in only two dimensions, there are still orientations which are scarcely detected.
US 4679046 contemplates the addition of a third antenna, with its plane perpendicular to the other antennae, to cover the other dimension, but concedes that this is undesirable because of the cost involved in adding another component, especially since it too must either be multiplexed or given a phase shift, and because of the extra power required to give the system enough coverage.
Enough power needs to be provided to the antennae to give their fields enough range to cover the detection zone involved. In addition to the cost of providing power, the power available for antennae is limited by
laws governing radio frequency radiation emission. The antennae divide the power between them; so more antennae need more power to achieve the same range. Thus, it is strongly desirable to use fewer antennae to save components and costs.
See US 4798175 and US 2002/0109636 Al for some further proposals in this field.
SUMMARY OF THE INVENTION A first aspect of the invention is a new antenna arrangement for detection/identification of animals, particularly but not exclusively livestock, with a good ability to detect/trigger identifier devices reliably over a full range of orientations without needing complex and expensive apparatus refinements.
Related aspects include methods of detecting and identifying animals using the systems comprising such antennae, and animal identification systems comprising the antennae in conjunction with other components.
A second aspect of the invention is concerned with methods and apparatus for identifying/detecting in particular situations, specifically in relation to transport, treatment, inspection, testing or restraint of the animals, or any combination of these. Preferably these methods and apparatus use the novel antennae of the first aspect, but they may use or incorporate other kinds of antennae or other detectors.
A third aspect relates to the incorporation of an antenna in a restraining crate or crush for identifying animals restrained there e. g. while they are subjected to
some treatment, testing, checking, measuring or diagnosis.
The aim in the first aspect is to provide an antenna which with two parts is capable of providing a field with components in three dimensions, i. e. able to actuate/detect transponders at any orientation. A preferred aim is to provide fields of comparable strength in three dimensions with only two antenna parts. A novel shape and relative arrangement of the two parts allows the antenna to provide the field without the need for a phase shift to be introduced between the parts. In other words, the arrangement of the two parts can be such that mutual inductance allows for an overall field with a very wide range of directional components, enabling detection of transponders in a correspondingly wide range of orientations.
The first aspect of the invention provides an antenna system for use in the detection/identification of animals carrying electromagnetic identifiers, particularly RF identifiers and most particularly transponders. The proposed system comprises first and second antenna loops, whose disposition is described herein in relation to a detection zone in which identifiers to be detected will be present. The detection zone can be regarded as having a longitudinal axis, typically corresponding to or aligned with the horizontal length of an animal to be detected in the zone in use, and in certain preferred embodiments corresponding to a transit axis or detection path
corresponding to the direction of movement of an animal or animals through, or into and/or out of, the detection zone in use. Considering the detection zone to have first and second sides opposed to either side of the axis, the system provides a first antenna loop which is a side loop disposed at and extending along the first side of the detection zone. This side antenna loop, or more strictly the layer locus that it lies in, may be curved but is preferably planar or substantially planar. The second antenna loop bridges or straddles the detection zone, having first and second wing portions opposed across the detection zone, extending longitudinally at the first and second sides of the detection zone respectively and connected by traversing portions of the loop which traverse between the first and second sides around the detection zone. At the first side of the detection zone the first loop overlaps the second loop and preferably they lie in substantially the same layer locus or substantially parallel layer loci-preferably substantially planar as aforesaid-on this side. The loops are generally, as in prior art constructions, open area-defining loops.
Preferably the or a longitudinal extending portion of the second loop on the first side traverses the opening defined by the side loop at an intermediate position thereof, dividing its area circumferentially with respect to the detection zone axis. Or, the side loop longitudinal run traverses the wing of the second loop. Preferably each portion of the area so divided is
at least 20% of the area. Preferably the first and second loops are substantially longitudinally coextensive, at least on the first side and preferably overall. For example preferably neither has less than half the longitudinal extent of the other, at least at the first side.
In use, the absolute orientation of the antenna loops is not critical provided that they create an effective detection zone of appropriate height and width, taking into account the likely variation of positions of identifiers to be detected, which in turn will depend on the size of the expected animals and the positions of their identifiers (ear tag, ruminal bolus etc. ). Usually however it is convenient to have the side loop actually beside the detection zone, so that it may be mounted in or on an upright structure such as a wall, fence or barrier which acts also as a restraint or enclosure for the animals. The traversing elements of the second loop may then cross above or below the zone, the animals walking or standing underneath or on top of them. This is mentioned here because for ease of subsequent description the following definitions and explanations will use apparently absolute orientations such as"up", "down", "above"and"below"and analogous terms, as if with reference to an embodiment in which the traversing elements traverse above the detection zone or path.
However the descriptions concerned will apply equally to embodiments in other absolute orientations unless the context clearly requires otherwise.
Clearly the dimensions of the arrangement will depend on the animals concerned, but typically the width spacing of the opposed parts of the antenna system will be at least 300 mm, usually not more than 1500 mm. The longitudinal span of each of the loops is typically at least 20 mm, usually not more than 1500 mm. The"depth" of the side loops and side loop portions is typically at least 300 mm. The sections or wire runs of each loop may be smoothly curved but more preferably are arranged as substantially linear segments with corners in between.
Thus, the"wings"of the second loop may have longitudinally extending parts, which may be substantially parallel with the zone axis, connected to one or both of the transverse sections by one or two riser portions. The transverse sections may arch over the detection zone in a curve, or in a straight line.
The depths of the first and second wing portions of the second loop may be substantially the same.
Preferably their depth is less than that of the side loop, with the longitudinal portion of the second wing portion opposing the open area of the side loop.
It will be appreciated that the second antenna loop may take the form of a saddle straddling the detection zone or path, taking the form of an arch, U or inverted U when viewed end-on.
Preferably the arrangement is symmetrical as between the two ends so as to operate similarly for movement of animals in either direction.
We have found that the antenna arrangement described is particularly effective for providing a detection field acting in all three dimensions effectively over the detection zone, requiring only two loops whereas other systems have compromised or accepted the need for further loops. Furthermore we find that the present arrangement has a relatively benign mutual inductance between the loops so that the two loops can be operated simultaneously without creating dangerous"dead spots".
This means that the system can be operated without phase shift and/or without multiplexing, and preferably is so operated and the other components of the system need not provide for these. In fact the two loops can be created from the same length of wire, because they may operate simultaneously in-phase.
The winding directions of the two loops are preferably opposed, in the sense that the longitudinally extending part of the second loop on the first side is wound in the opposite direction to the bottom of the side loop on the first side.
As known, the respective loops can comprise a single cable wound and supported in the desired shape of the loop, preferably with plural windings. Preferably, a low resistance wire is used. More preferably, twin core cable e. g. speaker cable is used. When connected to an AC power source, each loop may form part of a series resonant circuit, whereby the transmitted signal is produced when the current moves through the coils making up the antenna.
The antenna may be attached to a tuning module which tunes the capacitance and/or inductance of the circuit so that its resonant frequency matches the frequency of the current. The connecting wires are preferably coaxial, e. g. ethernet cables. Coaxial cables have minimal field emission; it is desirable in the antenna system to concentrate the field to the loops-the connecting wires should not lose power by emitting unnecessary fields. A tuning module can be used to adjust the values of capacitance and/or inductance to compensate for the capacitance and inductance present in the wires connecting the power source to the antenna. As with any arrangement where two field producing coils are placed in proximity to each other, the fields are affected by mutual inductance between the coils but as mentioned this is surprisingly not a problem. As mentioned, it is preferable to wind the wires making up the two loops in opposite directions. Thus, viewing the antenna from one side, if the first loop is wound clockwise, then the second loop is wound such that the portion nearest the first loop (comprising a leg of each n and a joining wire of the middle section) opposes it, i. e. it is wound anticlockwise. This is illustrated in Fig. 8, and helps to avoid dead zones where e. g. energising a transponder is unlikely.
In short, we can provide a tri-axial single phase antenna comprising two loops which provide an electromagnetic field capable of detecting all
orientations of transponder without needing to introduce a phase shift between the loops or multiplex them.
In livestock markets there is often a need to move a large number of animals through an identification station. Typically, e. g. cattle are identified by driving them through narrow races which allow only one animal through at a time. To speed up this process, several races may be used at once.
Presently, there are two types of transponder: half duplex (HDX) and full duplex (FDX). HDX transponders require silence (i. e. no transmittance by antenna) to respond and be detected, whereas FDX transponders respond by effectively reflecting the transmitted signal. These two requirements are obviously conflicting. However, it is desirable to have an antenna system capable of detecting both types. To do this efficiently whilst avoiding conflict requires an intelligent system that can react to responses it receives. Such intelligent arrangements are known, but a problem arises when one tries to apply them to antenna systems which try to cover two or more dimensions using e. g. two separate antennae (e. g. US 1599120). In this situation, the antennae may issue conflicting instructions, e. g. if the top antenna wanted to listen for an HDX signal but the side antenna wanted to measure an FDX signal. An advantage of the present system is that, because it can be considered as (or indeed be) a single antenna length detecting all orientations of transponders, conflicts as outlined above is avoided so that"intelligent"arrangements for
enabling detection of both HDX and FDX transponders are readily applied to it. The result is an antenna system which has a greatly improved accuracy and efficiency in detecting transponders.
Low frequency (e. g. RF) signals are preferably used in the detection of transponders, but the antenna system described herein will work at other frequencies. Low frequencies are preferred because they travel through walls and animal tissue more easily; this is well-known.
This aspect of the invention includes an antenna system as described, optionally combined with one or more of corresponding tuning module, power source, transponder reader system (which may be converted, or which may adopt the special configuration described: this is an independent proposal herein). Also, the antenna loops in conjunction with or mounted in or on a shaped support causing them to take up the prescribed disposition relative to a detection zone. Also, a method of detection using the antenna system, and particularly in which the antenna is used to excite transponders in the detection zone or path and the signals from the transponders are detected. This may be a method of monitoring livestock, for example, and the antenna system may be correspondingly adapted for mounting on/over the barriers of a livestock passage, race, restraint or other enclosure e. g. a stall or milking station.
A particular new proposal herein is a restraint cage or crush ; this is a prefabricated and optionally portable restraint unit having side walls, top and bottom
transverse supports supporting the side walls at a spacing appropriate to the animal concerned, preferably a built-in floor for the animal to stand on and restraint means for holding an animal in position in the unit, such as a pair of opposed side flaps which can be swung in to either side of the animal's neck behind its head.
According to our proposal an antenna for use in detecting an identification device on/in an animal is incorporated into the structure of the restraining cage, with the sides of the cage typically corresponding to the first and second sides as defined above and the transverse portions of the second loop traversing either above or below the space in which the animals stands when restrained. These restraints are normally used on a through-flow basis i. e. the animals enter at one end and leave at the other, and incorporation of a detection system is particularly valuable in view of the operations which are typically carried out in the restraint, which frequently will benefit from the ability to identify the animal on which the operation is carried out, and display and/or record the corresponding data in conjunction with the fact of that operation having been done, or data pertaining to it. Operations include weighing, testing for certain diseases, cleaning or clipping, trimming hooves, dehorning and the like. Preferably the antenna system accords with the first aspect above, and the variants and preferences described above are applicable.
Preferably the wire (s) forming the antenna loops is/are enclosed in structural or protective elements of the
restraint, to protect them against accidental damage. It may be for example contained between wall layers or passed through tubular frame elements.
The advantages in being able to deal with large numbers of animals, obtaining identities quickly and reliably, will be apparent.
In general terms, what we propose in the second aspect of the invention is to subject animals to detection as they move off or onto a transporter (lorry, van or trailer) by means of detection apparatus on or adjacent the transporter. The detection apparatus may be mounted at or adjacent the transporter door opening, either temporarily or as an integral part of the transporter entry/exit structure. Transporters may be fitted with suitable detection apparatus on manufacture, or conventional transporters may be modified to include such apparatus. We also propose various transporter modifications enabling better operation of the detector system.
These proposals have various advantages. One is that the possibility of animals straying undetected is reduced; they can be detected as they leave the transporter in which they arrive. A second advantage is that the person using the transporter can be confident of the kind of detection system which will be used, because it can be incorporated in the transporter. A further possible benefit is to provide a double-check.
More particularly, it becomes possible to obtain and store, in a reliable, automated manner, data specifically
relevant to the transportation of the animals in association with their identities. Such data may include any one or more or all of transporter (lorry/trailer) identification, animal origin, destination, number of animals in the load, purpose of transport, date, time and duration of trip, time of rest stops etc,'in addition to more routine data such as owner particulars.
The recording and handling of such data, and the provision of data processing apparatus programmed to do it, are further preferred aspects of the methods and apparatus described here.
A first part of the second aspect of the invention is a method of detecting and/or identifying animals carrying electronic identifiers, in which the animals are subject to the action of a corresponding detection system as they leave or enter a transporter, at least part of the detection system preferably being mounted on or adjacent to the transporter's entry or exit structure.
A second part of the second aspect of the invention is a transporter entry/exit structure e. g. the doorway itself, or any one or more of ramp, gate or roof/canopy components mounted at the doorway, comprising (or comprising a mounting for) one or more detector system elements, especially one or more antennae. A third part of the second aspect is a transporter having such entry/exit structure, and a fourth part of the second aspect is a method comprising adapting the entry/exit structure of a transporter by the incorporation of one or more said detection system elements.
Many livestock transporters have a doorway with one or more inner transversely-opening gates and a ramp door which opens downwardly. The gate (s) hold the animals in while the ramp is being raised or lowered, and when opened project out as side guide barriers for animals going up or down the ramp. Antenna structures-e. g. one or both of transmitting and detecting antennae-may be mounted in or on a gate of this kind, in a manner analogous to their conventional mounting in the side barriers of the races referred to previously.
Furthermore, the entry/exit structure of the transporter may have other features to improve detection.
One preferred proposal is to adapt one or more side barrier elements of the structure (e. g. transversely- opening gates as mentioned above) so that they can be held so as to define a transverse exit opening narrower than the transporter doorway, reducing the number of animals passing the detector location at a time.
Naturally a single file is ideal and the corresponding width of the restricted opening would depend on what kind of animals, e. g. cattle or sheep, were involved.
Typically it might be from 0.5 to 1.5 m. Typically the restriction might be to 50% or less of the full doorway width. Various means may be provided for maintaining the restricted width, e. g. connectors engageable between the side barriers and a ramp beneath, or with the ground, and/or locking connectors that can engage directly between the side barriers at ground level and/or at overhead level.
A further option is to provide side barrier extension portions adapted to define a restricted-width corridor, e. g. beyond an initial convergence where initial side barriers reduce the width from the full doorway width to a restricted width. Such extension portions may be separate barriers attachable to outer extremities of the initial barriers, or be pivotally mounted on the latter so that they can conveniently be folded in and out of position as needed.
The exit structure may also include an overhead portion. One possible function for this, implying a corresponding necessary structure, is to carry a detector or part of a detector, especially an overhead antenna element or antenna element portion. Additionally or alternatively, the overhead element may function as a mechanical spacer between side barriers, i. e. for a restricted-width opening as mentioned above.
Preferably the antenna system used accords with the first aspect above.
Preferably the detection system is connected or connectable to a control processor in the transporter.
Where the transporter is a trailer, the control processor may be in a towing vehicle, the trailer having detection system connections for it. Typically an on-board control system will include one, more or all of: means for powering the antenna (e), reader circuitry for converting received transponder signals into a storable form, and electronic storage means for recording received data relating to animals detected. There may be a portable
e. g. hand-held data logger to receive the load/trip data.
Additional or alternatively the data may be transferable by downloading to a master system of another computerized data system e. g. at a farm, abattoir or market.
The above control/recorded features may also be available in the other aspects described.
Embodiments of our proposals will now be described in more detail with reference to the accompanying drawings, in which Fig. 1 shows a perspective view of a simple loop antenna; Fig. 2 shows a plan view of the antenna of Fig. 1; Fig. 3 shows a perspective view of an antenna system which is an embodiment of our proposals; Fig. 4 is a plan view of the antenna of Fig. 3; Fig. 5 is an end view of the antenna of Fig. 3; Fig. 6 is a side view of the antenna of Fig. 3; Fig. 7 is a perspective view of the antenna positioned in a race; Fig. 8 shows an example of how the loops are wound in the antenna of Fig. 3; Fig. 9 shows a schematic circuit diagram for the antenna of Fig. 3; Fig. 10 is a perspective view of a simple loop antenna located in a side wall of a race; Figs. 11 to 14 show (schematically) trailer exit structures in various stages of opening, and
Fig. 15 is a schematic perspective showing a disposition of detection system elements in one exit structure.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS We disclose here a particular arrangement of wound coils to give an electromagnetic field suitable for energising transponders at any orientation. To illustrate the effect of field radiation from a current loop, Fig. 1 shows a simple loop antenna. The loop is made of several turns of cable and is connected in series to a tuning module and a power supply (not shown). This is then a series resonant circuit capable of tuning by the tuning module (which can vary the inductance and/or capacitance of the circuit compensate for inductance and/or capacitance). When current flows through the antenna (e. g. at resonance), an electromagnetic field is produced. The field resembles a toroid around the axis of the antenna wire. Figs. 1 and 2 show typical field lines. The size of the current affects the size of the toroid; the curvature of the lines through the loop can be reduced by increasing the current. Thus a loop aerial could be mounted on the side of a race or other structure with its plane parallel to the transit axis thereof, having high enough current so that the field lines through its centre extend substantially horizontally across the race. This is the idea behind known antennae used for cattle identification.
The antenna shown in Fig. 3 is made up of two rectangular loops: a flat loop 1 and a saddle loop 2,3.
The saddle loop has two n-shaped ends 3 bent perpendicular to a middle section comprising joining wires 2 which extend perpendicularly to the plane of both ends 3 to connect corresponding legs of the n's. Both loops are made of turns of twin core speaker wire.
Usually, three turns are used, but in principle, any number of turns may be used. The antenna is formed by positioning and supporting the loops adjacent each other so that the plane of the n-shaped ends 3 and the plane formed by the joining wires 2 are both substantially perpendicular to the plane of flat loop 1. The plane formed by the legs of the ends 3 and the joining wire 2 closest to the flat side loop 1 is actually in the plane of the side loop 1. The loops are wound in opposite directions as shown in Fig. 8. If side loop 1 is wound clockwise then the saddle loop is wound such that the part of it closest to the plane of the loop is wound anticlockwise. In other words the longitudinal saddle wire segment closest to the side loop 1 is wound in the opposite direction to the bottom part of the side loop 1.
[Note : it is also possible to have the bottom of the saddle loop below the bottom of the side loop.] Fig. 9 shows a schematic circuit diagram for the antenna. The antenna is connected to AC power source via tuning module 5. In practice, the tuning module 5 is positioned as close to the antenna as possible to minimise the power lost in the cables joining it to the antenna. The connecting wires 6 are ethernet coaxial cables. Flat loop 1 and saddle loop 2,3 are connected in
parallel over the power source 4, but each form a series resonant circuit tuneable by the tuning module 5. In fact they can also be formed from a single wire.
Figs. 3-6 are schematic representations of the fields produced by the antennae when the antenna system is powered. Similarly to the plain loop of Figs. 1 and 2, the flat side loop 1 provides field lines 7 across the antenna in a first direction from through its middle.
The saddle loop 2,3 provides field lines in two mutually perpendicular directions 8,9 both of which are perpendicular to the first direction. The joining wires 2 act as if there is a loop in their plane, so produce field lines 8 extending upwards through the antenna system. Likewise, n-shaped ends 3 both act like loop segments to produce field lines 9 extending into the antenna system in directions substantially perpendicular to the other field lines 7,8. Each field affects the other wires, i. e. mutual inductance occurs, but the arrangement of the system means the fields cooperate to provide an overall field of complex shape having components in all directions within the box-like zone enclosed by the saddle loop 2,3.
Fig. 7 shows how the antenna can be used in a cattle market. A race 10 for guiding an animal 11 is shown.
The antenna is positioned so that the flat loop 1 is located in a side wall of the race with its plane parallel with the direction of the race. Thus the field lines 7 it produces laterally traverse the race from left to right as viewed in Fig. 7. The saddle loop then spans
the race, i. e. the joining wires 2 are located in the side walls of the race running parallel to the direction of the race, and the tops of the n-shaped ends 3 traverse the race above the head of the animal 11. Thus, the antenna is positioned so that the animal 11 must pass through the box-like frame of the bent antenna 2,3 where the complex electromagnetic field is present. Therefore, an ear tag containing a transponder will be exposed to field lines in all directions, and will be energised and emit a response signal whatever its orientation. The emitted signals are preferably read by the same antenna system, although a separate reader antenna may be provided if wished.
Fig. 11 is a top view of the rear of a trailer 101 whose conventional rear ramp door 102 has already been folded down to rest on the ground. A pair of conventional overlapping inner doors 103a, b is shown, in their overlapping closed position. Fig. 12 shows the inner doors 103a, b folded out, in a manner which is itself commonplace, to form side barriers. A first distinctive adaptation is that one or more loop antennae 106,107 of a detection system are mounted on the side gates 103a, b so as to energize and detect the transponders of animals as they leave the trailer. By this means, there can be complete confidence that every animal in the trailer passes the detector. The precise nature of the antennae 106,107 is not crucial; various types are known and may be used. Likewise the transducers and processing electronics connected to the
antennae may in themselves be conventional, and are not shown. However they are preferably mounted in the trailer 101, or in a vehicle (not shown) that tows it, and connected via appropriate connecting cables.
A refinement indicated here is that the side gates 103a, b are held in a convergent position so that a relatively narrow exit opening 118 is defined between them. This prevents too many animals from leaving at a time, and perhaps confusing the detection system. To hold the gates in this position against the pushing of oncoming animals, various forms of locking engagement may be used. For example the gates may have locking bolts that drop down to engagements on the ramp 102.
Additionally or alternatively, one or more overhead connectors 141 e. g. cross-bars may extend between the tops of the gates to keep them in position.
Figs. 13,14 show a refinement, in which each of the side gates 103c, d is pivoted at its distal end to a corresponding gate extension 131c, d by hinges 133. As shown in Fig. 14, these extensions 131c, d can be folded around to form a parallel-sided corridor whose width corresponds to that of the restricted opening 118 of Fig.
12, and ensuring a zone where animals are passing in single file for detection by the detection system.
Correspondingly the antennae 106,107 of the detection system are mounted on the extensions 131 rather than on the main gates 103, so that they face onto the parallel- sided corridor. Again, various means may be used to hold the corridor to its restricted width against the push of
animals trying to get through. The main gates 103 may be anchored e. g. as suggested above. Additionally or alternatively, connectors may extend in between the gate extensions 131 to hold their spacing. The picture indicates schematically an overhead connector 142, which may be added separately, or more preferably is itself pivoted along the top edge of one of the side gate extensions 131.
In addition to its mechanical function, the top connector 142 may provide (as indicated in Fig. 15) a carrier for the transverse elements of a loop antenna 108 extending across the top of the single-file corridor through which the animals pass. The virtues of such a folded loop antenna in conjunction with a side loop antenna are described with reference to the first aspect herein and particularly with reference to Figs. 1 to 10.
A further possibility (also available in the first aspect herein) is for traversing segments of the top loop to be separable e. g. by unplugging cable sections, from the side section (s) of that loop so that they need be installed only when the detection/identification is needed.
The skilled reader will appreciate that many variations are possible, in accordance with the transporter used and the kind of gates and antennae deployed. Some transporters use simple rigid gates which project out horizontally when opened, whereas some side gates have internal pivots enabling them to form a parallelogram slanting down along side the ramp 102.
Both types are possible, and raise in a self-evident manner different issues for the connection of gate extensions and antennae.
As regards the recording of data, the identity codes of the animals are stored in a data logging computer appropriate to the purpose in hand. It might be an on- board or hand-held processor, or a corresponding data control centre at a farm, abattoir, market or showground.
The data may be sent directly from the detector system to such a central control centre, or transferred via another store e. g. an on-board or hand-held processor. Data may be sent via plugged cable connections or via wireless transmission. Particular data items of interest in transporting livestock were listed previously, and any one or more or all of these may all be entered for each movement of stock. This logging system may include a clock system to verify loading and unloading times, dates etc.