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Mifare 14443A Application Note

13.56 mhz rfid proximity antennas
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mifare
13.56 MHz RFID Proximity Antennas
Revision 1.0
PUBLIC
Philips
Semiconductors
READER COMPONENTS
®
(14443A)
November 2002

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Summary of Contents for Mifare 14443A

  • Page 1 READER COMPONENTS ® mifare (14443A) 13.56 MHz RFID Proximity Antennas November 2002 Revision 1.0 PUBLIC Philips Semiconductors...

  • Page 2: Table Of Contents

    Philips Semiconductors Rev. 1.0 November 2002 ® 13.56 MHz RFID Proximity Antennas mifare (14443A) CONTENTS INTRODUCTION..................3 Purpose and Scope.................. 3 Abbreviations ..................3 Reference Documents................3 HOW TO USE THIS DOCUMENT............4 ® THE MIFARE RF INTERFACE ............5 Energy Transmission ................

  • Page 3: Introduction

    This application note is intended to support RF-related design–in of Micore reader ICs. The aim is to provide ® the required understanding of the MIFARE RF interface (ISO 14443A) to design application specific antennas and matching circuits to achieve the best performance for a communication with a contactless ®...

  • Page 4: How To Use This Document

    2 HOW TO USE THIS DOCUMENT ® The chapter 3 of this document shows the basic principles of the RF interface as it used with MIFARE . The general understanding of this principle helps to do a fast and reliable antenna design based on Micore reader ICs, but none of the given formulas (especially those in the annex) are necessary to design such an antenna.

  • Page 5: The Mifare Rf Interface

    PCD and a PICC. ® ® Table 1 gives a short overview on the MIFARE RF interface. Essentially the MIFARE RF interface follows the transformer principle, although both the PCD and PICC antenna of course are resonance circuitries as antennas usually are.

  • Page 6: Energy Transmission

    The energy transmission from the PCD to the passive PICC is based on the transformer principle. At PCD ® side an antenna coil is required as well as a card coil implemented in the MIFARE card (PICC). Figure 2 shows the basic principle and the equivalent electronic circuitry.

  • Page 7: Picc

    Due to the quality factor Q of the antenna the transmitted signal is deformed to the shape shown in Figure 3. ® This shape can be used to measure the tuning of the antenna. For details refer to the “MIFARE and I Code, Micore Directly Matched Antenna Design”.
  • Page 8 Figure 4: Data Transmission PCD PICC, Miller Coding ® The data rate of MIFARE is 105.9KHz, so the length of a bit frame is 9.44µs. A pulse in the Miller coding has a length of 3µs. A logical ‘1’ is expressed with a pulse in the centre of the bit frame.

  • Page 9: Data Transmission Picc Pcd

    Manchester Coding each bit is represented by either a raising or a falling edge in the centre of a bit frame. ® For the MIFARE principle this is shown on the right side of Figure 5: A logical ‘1’ is expressed with a falling edge in the centre of the bit frame.
  • Page 10 Philips Semiconductors Rev. 1.0 November 2002 ® 13.56 MHz RFID Proximity Antennas mifare (14443A) Figure 6 shows the relation between the time and the frequency domain of the load modulation. Due to the ≈ ≈ data rate of the Manchester code generates sidebands at both sides of the sub μ...

  • Page 11: The Pcd Antenna

    PCD are given and fix, only the PCD antenna size and the environmental influences have to be ® considered for the antenna design principle. For the details of the Micore antenna design refer to “MIFARE and I Code, Micore Directly Matched Antenna Design”.
  • Page 12 Rev. 1.0 November 2002 ® 13.56 MHz RFID Proximity Antennas mifare (14443A) x = 10cm D/cm Figure 7: Coupling factor vs. Antenna diameter Figure 7 shows the coupling factor k versus antenna diameter D based on the required operating distance of x = 10cm.

  • Page 13: Environmental Influences

    This causes a detuning of the antenna and a reduced operating distance. If two active ® antennas for an MIFARE application are positioned in a close distance a communication to the card will be disturbed.

  • Page 14: Antenna Shielding And Compensation

    Rev. 1.0 November 2002 ® 13.56 MHz RFID Proximity Antennas mifare (14443A) 4.3 Antenna Shielding and Compensation Three topics shall be discussed. Electrical Shielding The electrical shielding absorbs the electrical field generated by the antenna coil as well as the electrical field of the reader PCB.
  • Page 15 Philips Semiconductors Rev. 1.0 November 2002 ® 13.56 MHz RFID Proximity Antennas mifare (14443A) Ω 4.3.1.2 50 Matched Antennas An electrical shielding should be used to reduce the electrical field generated by the antenna coil itself. To build a shielded antenna on a PCB at least one with 4 layers should be used with the shielding loop on the top and the bottom layer.
  • Page 16 Philips Semiconductors Rev. 1.0 November 2002 ® 13.56 MHz RFID Proximity Antennas mifare (14443A) 4.3.2 COMPENSATION stray TGND Coax Cable Antenna open 1 active turn + 1 compensation turn stray Electrical Principle Implementation Ω Figure 10: Compensated 50 antenna To compensate the stray capacitance of the antenna another turn with an open end is added. Due to the transformer’s principle the induced voltage in the open loop is inverted.
  • Page 17 13.56 MHz RFID Proximity Antennas mifare (14443A) Figure 11 shows the two dimensional field of the circular antenna. The right part shows the field distribution. The highest field strength is generated in the area of the coil. The left part shows the magnitude of the field strength H over the distance d.
  • Page 18 ® 13.56 MHz RFID Proximity Antennas mifare (14443A) Now, as shown in Figure 13 a ferrite plane (µ =40) is positioned in between the metal plane and the antenna coil itself. The field strength very near to the ferrite increases, but this increasing of the magnitude is not combined with an increasing of the operating distance.
  • Page 19 Philips Semiconductors Rev. 1.0 November 2002 ® 13.56 MHz RFID Proximity Antennas mifare (14443A) Small reduced stray field Low shielding Reduced operating distance Reduced stray field High shielding Reduced operating distance Optimum distribution: Balance between stray field distribution and ferrite...

  • Page 20: Antenna Decision Guide

    ® 13.56 MHz RFID Proximity Antennas mifare (14443A) 5 ANTENNA DECISION GUIDE Micore is a single reader IC family, which is designed to achieve operating distances up to 100mm without external amplifiers. The design of the remaining passive RF part is straightforward.
  • Page 21 Philips Semiconductors Rev. 1.0 November 2002 ® 13.56 MHz RFID Proximity Antennas mifare (14443A) MF RC500 Matching circuit and antenna design Distance between reader and antenna ? directly connected or cable length> 30 mm cable length < 30 mm 50 Ohm matched...

  • Page 22: Annex

    It’s not necessary to know and use the below given formulas for the design of a Micore PCD antenna. The ® principle is described above and details for that design can be found in “MIFARE and I Code, Micore Directly Matched Antenna Design”.
  • Page 23 Philips Semiconductors Rev. 1.0 November 2002 ® 13.56 MHz RFID Proximity Antennas mifare (14443A) Optimisation of the coupling coefficient: ⋅ ⋅ ⋅ ω ⋅ ω ⋅ ⋅ B ˆ B ˆ ⋅ ω ⋅ ω ⋅ ⋅ ω ⋅ ⋅...

  • Page 24: Parameters And Units

    Philips Semiconductors Rev. 1.0 November 2002 ® 13.56 MHz RFID Proximity Antennas mifare (14443A) 6.2 Parameters and Units Induced voltage Number of turns Φ: Magnetical Flux time Magnetical Flux densitiy (Coil) Area Induced open loop voltage (card antenna coil) PCD antenna coil current...
  • Page 25 Definitions Data sheet status Objective specification This data sheet contains target or goal specifications for product development. Preliminary specification This data sheet contains preliminary data; supplementary data may be published later. Product specification This data sheet contains final product specifications. Limiting values Limiting values given are in accordance with the Absolute Maximum Rating System (IEC 134).

  • Page 26: Contact Information

    Philips Semiconductors - a worldwide company Contact Information For additional information please visit http://www.semiconductors.philips.com.Fax: +31 40 27 24825 For sales offices addresses send e-mail to: sales.addresses@www.semiconductors.philips.com. © Koninklijke Philips Electronics N.V. 2002 SCA74 All rights are reserved. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without any notice.

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