Design and Performances of UHF Tag Integrated Circuits
Design of UHF RFID tag IC presents unique design challenges to satisfy constraints due mostly to the remote biaising of the batteryless tag. After a brief introduction (section 1.1) and a presentation of the architecture (section 1.2) of a tag IC, section 1.3 will show the principles of converting RF into DC via voltage multipliers successively; first in the ideal then in the real case. The end of the section will deal with the influence of the active element (the diode or the MOSFET, a comparison between the two will highlight the pros and cons of each) and passive parasitics that must be taken into account during the dimensioning of the intermediate and the output capacitors. A simplified model of the antenna and the input of the rectifier will allow us to see the importance of matching and will lead to the computation of the Power Conversion Efficiency (PCE) of the circuit. Sections 1.4 and 1.5 propose a few up-to-date circuits with careful design to reduce the threshold voltage of the active element and improve the PCE. Sections 1.6, 1.7 and 1.8 rather briefly discuss the problem of exchanging information between the reader and the tag and the improvements on the oscillator design to reduce overall consumption. Sections 1.9 and 1.10 list the latest technologies, techniques and trends used in the digital part and lists of performances of the different teams are compared.
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