Technical Note - Part 2

An Outline of the ATL Automatic Identification System

The ATL automatic identification system is a development which significantly extends the range of applications of the TIRIS™ (TIRIS is a trademark of Texas Instruments Inc.) electronic identification technology.

The TIRIS™ system has several advantages over earlier electronic identification technology. The most significant being the performance of the reader and read range of the TIRIS™ tag. This is far superior to existing tags.

The basic TIRIS™ system consists of a reader, antenna and tags. The one disadvantage is due to the constraints imposed by the total antenna inductance of 27μH. This determines the size of the antennas and limits the distance between the antenna and the reader. In addition, either oxygen free copper or litz wire must be used to maintain good read ranges. As well as this, the use of one reader and one antenna is ideal for situations where continuous monitoring of moving items is required but becomes unnecessarily expensive where multiple antennas are required to read nominally static or slowing moving tags.

In these situations, continuous monitoring is not necessary and in practice results in expensive equipment being under used for much of the time. The ideal solution is to increae the number of antennas which are connected to one reader and activate each one either as and when required or in a regular sequence. The ATL automatic identification system provides just a solution.

The ATL Automatic Identification System

The ATL Automatic Identification system eliminates the constraints of the basic TIRIS™ system and extends the range of applications. The system was originally developed to identify dairy cows in the milking parlour but it is now being used for a number of applications related to animal feeding and could equally be effective in industrial applications having similar requirements.

Eliminating the constraint of the 27μH provides a number of significant advantages. The size and shape of the antennas is infinately variable, the antennas can be constructed with low cost plain copper cable, large numbers of antennas can be used with one reader and they can be operated at distances of several hundred metres using low cost cable with one reader.

For example, the ATL herringbone automatic identification system controls up to 96 antennas. Each antenna is 870mm high and 330mm wide. These are positioned at every stall in the milking parlour and the cable lengths to the reader vary from about 4 to 20 metres. The read range for all the antennas is maintained at between 800 and 850mm.

During operation only one antenna is active at any one time. This ensures that only the tag nearest to an antenna will be read and is ideal for the milking parlours since these is no possibility of the cows being identified until they enter the correct stall.

The Advantages of the ATL Automatic Identification System

1. Inductance of 27μH is no longer a constraint - Limits on size and shape of antenna, length of connecting cable and quality of wire for both no longer apply.
2. No constraint on the size of antennas - Antennas from a few millimetres in diameter up to 8 x 0.75 metres have been constructed and tested successfully. Antennas having a wide range of inductance values will operate successfully.
3. Multiplexing - Any number of antennas can be connected to one reader and multiplexed using low cost components. The normal tag read cylce of approximately 10 to 13 per second is used as the multiplex clock.
4. Triple-Axis Portal Antennas - A large walkthrough antenna for cattle using low cost cable and a formation of multiplexed coils enabling tags to be identified on all three axis. Tags at speeds of up to 3 metres per second can be identified within a space 800mm wide, 1800mm high and 1300mm long.
5. Low cost coaxial cable links antennas to reader - Coaxial cable reduces electronic noise pick-up with long lengths of cable.
6. Greater distances between reader and antenna - The read range of the Allflex cattle tag is about 50% of the maximum at a distance of 200 metres from the reader. The maximum distance at which antennas have been used with a TIRIS™ 2000 Reader is about 450 metres; read range at this distance is about 30% of the maximum.
7. Infinite numbers of antennas can be linked to one reader - Installations of several thousand low cost antennas are possible. They can be multiplexed or read in response to a sensor, to provide accurate information on the location or movements of a variety of items.
8. Low 'Q' antennas are used - Any low cost plain copper cable can be used to construct antennas.
9. Wide tuning range - Precise tuning is not required therefore a wider tolerance is available for the antennas in multiple antenna systems. Multimeters can be used for tuning in most instances.
10. Other technologies - The antenna system can be used with both FULL and HALF duplex technologies operating at 134.2kHz. Tests with a Dual ISO reader suggest that the system will operate equally effectively with all the lower frequency technologies which are inductive.
11. Proximity of Antennas - Antennas can be operated in very close proximity without problems of interference since only one reader is used.

ATL automatic identification technology is protected by international patents.