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RFID transponder technique is associated with various applications and usage scenarios. There are tags for wireless identification and tags that are able to store extended object information as well as including a data logging function, an actuator or a sensor. Besides passive UHF and microwave tags which provide long-range communication but only small energy transfer of some μW, inductively coupled passive tags can be better used for even sensor applications, today. In that case, the power consumption of the tag can be up to some mW (Finkenzeller, 2007) to power sensors as well as analogue and digital circuits for an extensive signal processing. A lot of physical parameters like acceleration, force, humidity, pressure or temperature can be measured. Whereby, many well known sensors and measuring principles can be implemented directly. Such sensor tags but also others using LF and HF frequency range can be used in various industrial applications like process monitoring or automation. Just as complex and implantable diagnostic systems are available in medical engineering. Each of these RFID based applications need a customised design to optimise wireless energy transfer and data communication, because each application has different electrical, electromagnetic and geometrical demands. Therefore, antenna design is an important part of the whole system design. Both reader and tag antenna must be optimised taking into account a free air transmission channel or additional eddy current losses because of existing metals or fluids. Other important constraints considered are the specified maximum or minimum antenna dimensions, shape and used material, different link distances, arbitrary coaxial and noncoaxial antenna positions or tag rotation. Besides these mostly electromagnetic and geometrical properties, electrical system properties like power of the driver, demodulator sensitivity, approximated load resistance of the tag, used protocol, bandwidth or parasitics also influence the design process. For a system designer an important question is if a particular RFID technique can be implemented and used successfully. Principally, an answer can be found using a lot of experiences, numerical simulations for antennas and extensive verification in the lab requiring prototypes and measurement setups. Thereby, system optimisation is done manually. But that standard design flow could be very time consuming and expensive because of producing many different prototypes and using complex measurement setups in the lab to characterise the transmission channel. Additionally, it is not sure that the best Source: Radio Frequency Identification Fundamentals and Applications, Design Methods and Solutions, Book edited by: Cristina Turcu, ISBN 978-953-7619-72-5, pp. 324, February 2010, INTECH, Croatia, downloaded from SCIYO.COM |
