Batteryless tags transfer secure information

Inductively coupled RFID technology has been adapted to both acquire data wirelessly from fast moving or hard to access objects, and also to work with smart locking and unlocking of containers and packages. The use of inductive coupling rather than radio ensures that there is no need for batteries or oscillator crystals, so that functioning can be guaranteed at high ambient temperatures and at any time. This is particularly useful in the case of locks, which can be powered totally externally and which can be buried deep within packaging with no external access. The inductive sensing has been applied to conditioning monitoring of pistons working within engines and to sensors monitoring conditions in the mouth for dental research. Inductively coupled coded locks have been demonstrated on various containers, particularly those targeted at the secure containment of pharmaceuticals. The idea is the brainchild of Dr Greg Horler, a lecturer in the Department of Electronic Engineering at the University of Leeds. It is now embodied in the form of a spinoff company of five persons named Instrumentel, assisted by an initial investment by the White Rose Technology Seedcorn Fund. Having no battery or crystal oscillator ensures that sensing and actuation can be undertaken in extreme, hazardous or difficult to access environments where batteries or crystal oscillators are impractical or incompatible. However, most practical applications conspire to affect the mutual inductance deleteriously. Furthermore, in the case of an engine piston, the rapid up and down movement modulates the mutual inductance and can modulate the sensed data as well. One of the key technologies developed by the company has been a computer tool to model performance as a function of system parametrics. The tool has been found to closely model real world experiments and is now being further developed to create an integrated design environment. Without a battery supply, all aspects of the system must be optimised and the circuit made to operate at the lowest possible power levels. Furthermore, the incident radio frequency field, while delivering the necessary power to the sensing tag, also bathes the tag's power, signal and data lines in radio frequency that can affect performance. Dr Horler said that many of the problems associated with inductively coupled circuits are remedied by good circuit design. Maximising performance is a matter of maximising the mutual inductance. Since every application is different, however, a great deal of practical 'know how' has had to be acquired through practical experiments involving the variation of coil sizes, number of windings and coil size. As an example, he said that purely theoretical formulae and modelling does not provide adequate answers to the problem of establishing the mutual inductance between two co-axial concentric coils, one attached to an aluminium piston, with both coils contained within a steel bore and threaded by a titanium connecting rod as found in a Formula 1 engine. To date, all systems have been constructed from discrete components. Current technology, in the form of an inductively powered temperature sensor system, was demonstrated in April to attendees to the IEE seminar on "Telemetry and Telematics" in London. We were told that the demonstration system was limited to working to 125 deg C but Dr Horler revealed that he intended to extend this to 300 deg C using silicon on insulator technology, and that devices would eventually be made available as single chip ASICs capable of working at that temperature. Working frequency of demonstration devices is 13.56MHz, with a useful range of 0 to 10cm and able to transfer data at up to 9600 baud. Antennae are printed around the peripheries of the circuit boards. The technology is to be commercially marketed under the brand name, 'Intrasense' from later this year. Even in their present form, with two independent sensing channels and identification codes, the units weigh less than 5g. As well as meeting the needs of engine development teams, the devices have been used to measure the temperature of work pieces and friction probes in friction stir welding. In addition, we learned that a system has been developed for use by the Leeds University Dental School, for measuring plaque pH in the mouths of patients. But it is the coupling of the technology to 'Smart' locks for packaging which offers the biggest potential market. Dr Horler was able to demonstrate pots with lids with coded locks that could be inductively locked and unlocked. In this application, a tag with the electronic locking means is embedded either in the container or the lid. The lock is controlled by the reader via the tag. This solution avoids all problems arising from tags that can be removed, either deliberately or accidentally and locks that can be accessed from outside. The pot we were shown could only be opened when placed within the electromagnetic field of the reader and subjected to a secret access code. In another device, a lock has been designed to be retro-fitted to a sea going container, so that the identifier tag cannot be removed without tearing the container apart. Many companies, particularly in the food and pharmaceutical businesses are becoming quite paranoid about ensuring the integrity and thus the guaranteed traceability of their goods as they pass along the distribution chain. Labels, barcodes and RFID tags are all liable to come off, even if they are not deliberately removed. Concerns are not only about possible threats from criminal or terrorist groups threatening or succeeding in contaminating products, but also to avoid substitution of product by inferior alternatives en route. Petty theft also is far from a petty problem. Every large retail company and supermarket chain suffers from it, as does the military, particularly during war. Theft from US forces during World War II was legendary and although precise figures are hard to come by, the problem is unlikely to have been greatly reduced since. Dr Horler declined to reveal the mechanical details of his company's inductively powered locks. Examination of the locked pot top revealed that when it was engaged, it gripped on all sides, and was not limited to a single catch. The technology is to be marketed under the brand name, 'Intralock'. Instrumentel Dr Greg Horler IEE RF & Microwave Engineering Professional Network Eureka says: While inductively coupled telemetry provides another useful tool for the research laboratory, inductively coupled coded locks on transport containers could become totally ubiquitous in supermarket, pharmaceutical and military supply chains. Pointers * Inductively coupled wireless telemetry overcomes problems imposed by need for batteries and/or crystal oscillators in conventional low power radio systems. It can, potentially, therefore be used at much higher ambient temperatures * Inductively powered RFID tags can be incorporated into coded locking systems, with all working parts protected from deliberate or accidental damage by being buried deep within the containment construction * The inductively coupled telemetry is to be offered commercially from later this year. The inductively coupled lock telemetry has been demonstrated, but is presently in need of development partners.