A novel ultra low power ASK demodulator for a passive UHF RFID tag compatible with C1 G2 EPC standard protocol
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A novel ultra low power ASK demodulator for a passive UHF RFID tag compatible with C1 G2 EPC standard protocol Maryam Gharaei Jomehei • Samad Sheikhaei Behjat Forouzandeh
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Received: 8 August 2012 / Revised: 22 January 2013 / Accepted: 24 January 2013 / Published online: 8 February 2013 Springer Science+Business Media New York 2013
Abstract In order to reduce the power consumption of RFID tags and increase the reading range of RFID systems, this paper proposes an ASK demodulator that uses a new approach to reduce the threshold voltage of diode connected MOS transistors as an obstacle in the design of the envelope detector. Also, an ultra low power comparator is used for further power reduction. This circuit has been simulated in a 0.18 lm CMOS technology to satisfy EPC Class 1 Generation 2 standard protocol emphasizing on the reduction of power consumption. The proposed circuit can correctly demodulate the minimum input RF signal amplitude of 180 mV for modulation depths of 55–100 % with 40–160 kb/s data rates. A total power consumption of less than 290 nW is achieved at a 1.2 V power supply. Effects of the input signal additive white noise as well as the process and temperature variations on the signal demodulation is also investigated in this paper. Keywords ASK demodulator Dynamic comparator Modulation index Radio frequency identification Ultra low power White noise
1 Introduction Today’s RFID systems have attracted more and more attentions of industries and academic centers for their low cost and extensive applications. It has motivated their efforts to improve RFID technology especially UHF RFID tags [1]. One of the major goals of these efforts is the M. G. Jomehei (&) S. Sheikhaei B. Forouzandeh Nanoelectronics Center of Excellence, School of Electrical and Computer Engineering, University of Tehran, Tehran, Iran e-mail: [email protected]
improvement of the operating range, which is desired for many RFID applications, such as supply chain management, intelligent transportation systems, etc. [1, 2]. This improvement can happen in readers or tags design. Because of cost issues, it is efficient to improve functionality by optimizing the tag design. The RFID tags can be categorized by their power supply. Active RFID tags are used in some applications due to their higher communication range and simpler structure because of their external battery which provides the supply voltage. So, there is no need to extract power from the input signal. However, because of their battery, the final product would have a larger size and higher weight and would need battery replacement over time, which leads to higher total system cost. Therefore, their applications are limited to the cases where high reading range is needed and higher cost can be tolerated. Passive RFID tags occupy a major part of the market, since they do not need battery and have lower cost than active tags. In passive tags, power is extracted from the reader transmitted RF signals [3]. The data is also modulated on the RF input signal. The d
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