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RFID TECHNOLOGIES matching network (MN) and the PCB pattern. It then generates an external antenna. the LEDs operate as status interrupt to bring the MCU out of sleep indicators. In a system based on this mode. the MCU reads the RssI and reference design, an active tag can be the base station ID contained in the expected to operate for a typical period LF signal. The tag will have a defined of three years on a small CR2032 coin UHF transmission time slot assigned cell. to its ID. to conserve power, the tag goes into sleep mode again until this System operation time slot arrives. During the reserved the base station works in the follow- time slot, the tag establishes a 2.4GHz Fig. 3: the ams active RFID demonstration system. ing manner. the MCU initializes the connection with the base station, pairs LF wake-up receiver and the UHF transceiver with updated with it and streams a data packet. afterwards, the tag goes into register settings. It then transmits the LF wake-up signal. after sleep (LF receive) mode again. the LF transmission, the MCU switches the 2.4GHz transceiver to receive mode, waiting for active tags to respond. When a A low-power active RFID implementation tag responds, it needs first to be temporarily paired to the base the advantage of the architecture described above is its ultra- station. Once the devices are paired, one streaming data packet low power consumption, the result of keeping the UHF trans- is expected. the tag’s ID and RssI information are contained mitter in almost permanent power-down mode. this is enabled in this packet. (If pairing is not accomplished, the base station through the use of an LF wake-up receiver, the AS3933, which will issue a second temporary pairing command after a period features a Manchester decoding capability. this allows the of time.) as soon as the packet has been streamed, the base implementation of pattern recognition, so that the system station switches back to receive mode, waiting for another tag avoids false wake-up calls generated by noise or interference. to respond. Thus the AS3940 UHF transceiver only operates when in the The tag’s operation mirrors that of the base station. On vicinity of a base station. the rest of the time, the tag draws just power-up, the MCU initializes the LF wake-up receiver and the a few microamps. UHF transceiver. the RC oscillator of the LF wake-up receiver as well as achieving outstandingly low power consumption, is calibrated and the 3D antenna is automatically tuned by the the highly integrated design is also small and has a low bill of AS3933. After this, the tag goes into deep sleep mode, waiting materials - see figure 3. It has been successfully implemented for an LF wake-up signal. Once a wake-up signal is received, in a number of end products, including access control and real- the device checks that its pattern corresponds to its reference time location systems, and in passive keyless entry systems. Enhanced RFID realizes its full potential By Victor Vega FROM ADDING vISIBILITyTO the production process, through work-in-process manufacturing techniques, to adding account- ability and speed to the movement of finished products through the supply chain, RFID has already changed the way manufac- turers of electronics operate. But a number of challenges and shortcomings have limited the benefits the technology delivered. For example, product housings made of metallic or other types of conductive materials often present an obstacle when using off-the-shelf RFID labels, because the surfaces block the RF signal transmitted by readers and make the tags difficult to read. additionally, an RFID label attached to the exterior surface of a product can easily be found and removed - a weakness that The UCODE I2C chip enables full product authentication fro- could be exploited in order to divert goods to the grey market or massembly lines to retail shelves. disassociate a product from its warranty records. What’s more, applying RFID tags to the exterior surface of customization (languages, features and functionality), theft/brand electronic products after they’ve already been manufactured robs protection, and the ability to wirelessly track or trace products the manufacturer of the added visibility and control the technol- throughout the entire product lifecycle. ogy could provide throughout the entire manufacturing process. NXP’s UCODE I2C technology, recently incorporated into the Reliable track and trace Murata Magicstrap RFID module family, is specifically designed As the UCODE I2C chip is soldered to the PCB, it stays in the to solve these issues. Ultimately, the tag improves the manu- product over its full lifecycle. this means that the integrated tag facturing process and product delivery by enabling enhanced enables a work-in-process tracking system that ensures fast, error-free assembly throughout production. this also enables it Victor Vega is RFID solutions director at NXP semiconductors – to provide relevant data at the recycling stage, delivering proof www.nxp.com - He can be reached at victor.vega@nxp.com of compliance to the WEEE directive and reducing associated costs. 44 Electronic Engineering Times Europe January 2013 www.electronics-eetimes.com


EETE JANUARY 2013
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