Trolley Scan

The staff at Trolley Scan were involved in the first developments of UHF transponders for retail applications, namely the development of Supertag in 1990 in Pretoria, South Africa. At that time we aimed to build a single chip transponder for use in tagging items in a grocery trolley. Then semiconductor technology was at such a stage of development... that there were analogue type devices which could handle RF components, and a separate type of technology was in use for digital circuitry for data handling. Hence we ended up with two chips on each transponder. About ten years later single chip devices were practical that had both the RF and the digital circuitry on a single device and single chip transponders became available. The transponders get their power from the energising field and to visualise the power distribution back in 1990, we made a number of small dipoles with light emitting diodes. Attaching these to the wall of the office and aiming the energising antennas at the wall from about 3 metres away, together with a fair size RF power generator, we could get the LEDs to glow if they were in the main beam and hence see the power distribution. Those devices needed about 54 milliwatts of power in the collecting area and had an operating range of about three metres with the transmitters and antennas we then used. The two chip transponders needed similar power. Since January 2004, Trolley Scan have been supplying 200uW versions of transponders, that is a 250 times improvement on the originals. We now have a new transponder which is also passive, is attached to metal items, and uses just 40 microwatts (uW) of power, that is 1350 times less power than the originals. This dramatic improvement over time, has meant greatly increased range for operation. It also has led to reduced energising power being needed from the reader, which means smaller RF amplifiers and the ability to use lower gain antennas which can spread the power over a wider angle increasing the area of coverage. The lower power needs of the new ...Read More