EMV Contactless
Payment Systems based on AS3911
Overview and System Simulations
Giuliano Manzi, PhD
Mannheim, May 23–25, 2012
CST EUROPEAN USER CONFERENCE 2012
a leap ahead in analog
• AS3911 OVERVIEW
• EMVCo OVERVIEW
• EMVCo History and Today
• EMV Contactless Specifications for Payment Systems Standard
• Reference PICC and PCD
• Analog / Signal RF Requirements
• Simulation Model Reference PICC PCD
• Reference System Simulations and Validation
• RF Power Validation (Simulations vs. Measurements)
• RF Signal Overview
• EMVCo System Modeling
• austraimicrosystems EMVco Reference Design
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OUTLINE
© 2011 austriamicrosystems
The AS3911 is a highly integrated NFC Initiator / HF Reader IC. It includes the
analog front end (AFE) and a highly integrated data framing system for ISO
18092 (NFCIP-1) initiator, ISO 18092 (NFCIP-1) active target, ISO 14443 A and
B reader (including high bit rates) and Felica™ reader. Implementation of
other standard and custom protocols is possible through using the AFE and
implementing framing in the external microcontroller (Transparent mode).
The AS3911 includes several features, such as low power capacitive sensor,
which can be used to detect a presence of a card without switching on the reader
field. Additionally, a presence of a card can be detected by performing a
measurement of amplitude or phase of signal on antenna LC tank and comparing
it to stored reference.
The AS3911 is also qualified for use in automotive applications which makes it
ideal for car access, ignition and diagnostic functions. The AS3911 is designed
for operation from wide power supply range from 2.4V to 5.5V, peripheral
interface IO pins support power supply range from 1.65V to 5.5V.
Applications
The AS3911 is suitable for a wide range of applications including EMV
Payment, Access Control, Automotive, NFC Infrastructure, and Ticketing.
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AS3911 OVERVIEW
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Antenna Tuning
Capacitive Wake-up
Minimum current @ 800 ms: 2,0 µA
Typical current @ 100ms:
4,7µA
Fast detection @ 10ms:
31 µA
Resonance increase the current that is flowing through
the coil.
AS391x optimize the resonance
Optimized resonance behavior will maximize current
Advantage: lowest current consumption
enables Battery powered system
Advantage: antenna management make the system
independent of parameter variances
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AS3911 – Unique Features
© 2011 austriamicrosystems
The EMV name comes from Europay, MasterCard and Visa, the companies that in 1994 initiated
development of the EMV Specifications. Europay International SA became part of MasterCard in
2002. JCB joined EMVCo in 2004, and American Express in 2009.
At the time, many banks recognized the benefits of chip-based payment but also realized that
international standards for such payment were needed to help foster global interoperability. The EMV
Specifications were created to fill that void.
The first version of the EMV Specifications was published in 1996, as version 3.1.1. The most recent
version, EMV 4.2, was published in June 2008.
Today EMVCo manages, maintains and enhances the EMV Integrated Circuit Card Specifications to
help facilitate global interoperability and compatibility of payment system integrated circuit cards and
acceptance devices. EMVCo maintains and extends specifications, provides testing methodology
and oversees the testing and approval process.
EMV chip-based payment card systems are now utilized in numerous countries around the world.
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EMVCo History and Today
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DEFINITION
The basic components of a contactless system are the contactless reader or Proximity Coupling Device
(PCD) and a transponder or Proximity IC Card (PICC).
The PCD is an antenna connected to an electronic circuit. The PICC consists of an inductive antenna and
an integrated circuit connected to the ends of the antenna. The combination PCD – PICC behaves like a
transformer. An alternating current passes through a primary coil (PCD antenna) and creates an
electromagnetic field, which induces a current in the secondary coil (PICC antenna). The PICC converts the
electromagnetic field (or RF field) transmitted by the PCD, into a DC voltage by means of a diode rectifier to
power the PICC’s internal circuits. The configuration and tuning of both antennas determines the coupling
efficiency from one device to the other.
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EMVCo
© 2011 austriamicrosystems
DEFINITION
The RF energy transmitted by the PCD and received by the PICC not only powers up the PICC but is also
used to transport the data through modulation of the carrier. The PICC decodes and processes the data
and responds to the PCD by means of load modulation.
Load modulation is based on the electromagnetic coupling (i.e. mutual inductance) between PICC and PCD
similar to the power transfer and communication from PCD to PICC. The PICC changes the current in its
antenna. The current variation in the PICC antenna is sensed by the PCD as a small change in the current
in its antenna, typically sensed as a small increase in voltage across a resistor in series with the PCD
antenna.
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EMVCo
© 2011 austriamicrosystems
REFERENCE SYSTEM
Why a Reference System is needed?
The RF power and signal interface part of the specification is specified in terms of the EMVCo reference
equipment. EMVCo reference equipment consists of an EMVCo reference PCD, an EMVCo reference
PICC and an EMVCo reference CMR (Common Mode Rejection).
The purpose of the EMVCo reference equipment is to provide a PCD and PICC that cover the variations in
contactless technology. A PCD can therefore be checked against the EMVCo – Reference PICC and a
PICC can be checked against the EMVCo – Reference PCD.
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EMVCo
© 2011 austriamicrosystems
REFERENCE SYSTEM
The Reference PCD has a circular antenna of about 7 cm, which is in the small range of antenna sizes
encountered in EMVCo terminals.
Customer Trend is to have smaller and smaller PCD “antennas”
The circular antenna creates a symmetric field distribution from the z-axis, which simplifies measurements.
When fed with 600 mW into its 50 Ω input impedance at resonance, the EMVCo – Reference PCD provides
a magnetic field which is representative of most PCDs.
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EMVCo
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REFERENCE SYSTEM
The EMVCo – Reference PICC has an antenna similar to those found in ID-1 cards. (64 mm x 34 mm)
As payment products based on this specification the system is designed to work with only one PICC in the
PCD field and PICC it is tuned to 16.1 MHz. This is a compromise between power consumption, detuning
and communication capability.
The EMVCo – Reference PICC allows the analysis of the signal as sent out by a PCD. For analyzing the
frequency content of these signals, it is equipped with a pickup coil, which is an integral part of the EMVCo
– Reference PICC.
The EMVCo – Reference PICC can also send information back to a PCD, using various levels of load
modulation.
The EMVCo – Reference PICC can be configured with a linear and a non linear load. The non linear load is
self-adapting to the magnetic field strength. The (variable) load parameters are set based on the maximum
power consumption in current contactless cards. The maximum power consumption represents a worst case
scenario for a PCD.
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EMVCo
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OPERATING VOLUME
The Operating Volume of a PCD is the 3-dimensional space for which the specification imposes
requirements on the magnetic field HOV (Operating Field).
The Operating Volume is measured from the centre of the landing plane, along an axis perpendicular to the
landing plane. Requirements on this geometry suppose that the PCD is stationary and that the PICC moves
slowly (less than 1 m/s) through the Operating Volume.
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EMVCo
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RF signal power
Envelope shaping PCD to PICC
Envelope shaping PICC to PDC
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EMVCo
RF Requirements
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RF signal power
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EMVCo
RF Requirements
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PCD to PICC
The ISO/IEC 14443 standard defines two possible modulation types, called Type A and Type B.
For communication from PCD to PICC, both Type A and Type B use Amplitude Shift Keying (ASK). The
amplitude of the carrier is switched between V1 and V2 , creating a lower level when the field is at value
V2 . The requirements of the lower level as well as of the envelope of the carrier for the two modulation
types of ISO/IEC 14443 are defined in this section.
Type A communication from PCD to PICC uses the modulation principle of ASK 100%. The carrier is
turned on and off, creating a lower level when turned off. In practice, it will result in a modulation depth of
95% or higher. The lower level for Type A modulation is referred to as “pause” by ISO/IEC 14443-2.
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EMVCo
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PCD to PICC
PCD signal shaping
Type-A
The PCD shall modulate the Operating Field in the Operating Volume in such a way that the signal measured at the
output of the pickup coil of the EMVCo – Reference PICC has the following characteristics:
• The time between V4 of the falling edge and V2 of the rising edge shall be t1 .
• If V does not decrease monotonically from V4 to V2 , the time between a local maximum and the time of passing
the same value before the local maximum shall be t5 . This shall only apply if the local maximum is greater than V2
.
• Ringing following the falling edge shall remain below VOU,A V1.
• V shall remain less than V2 for a time t2 .
• V shall increase monotonically to V3 in a time t4 .
• V shall increase monotonically to V4 in a time t3 .
• Overshoots immediately following the rising edge
shall remain within (1±VOU,A )V1 .
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EMVCo
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PCD to PICC
PCD signal shaping Type-B
The PCD shall modulate the Operating Field in the Operating Volume in such a way that the signal measured at
the output of the pickup coil of the EMVCo – Reference PICC has the following characteristics:
• The modulation index (m i ) of the signal shall be mod i .
• V shall decrease monotonically from V3 to V4 (i.e. the falling edge) in a time tf .
• V shall increase monotonically from V4 to V3 (i.e. the rising edge) in a time tr .
• The rising and falling edges of the modulation shall be monotonic.
• Overshoots and undershoots following the falling and rising edge shall be less than
VOU,B (V1 -V2 ).
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EMVCo
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PICC to PCD
PICC signal shaping
For the communication from PICC to PCD, both Type A and Type B use load modulation. The carrier frequency fc is
used to derive a subcarrier with frequency fs equal to fc/16 (~847 kHz).
Switching a load on and off at this frequency creates the subcarrier. When the PICC is in the loaded state, a higher
current will flow through the antenna of the PICC than in the case where the load is not switched on. This difference in
current in the PICC antenna is sensed by the PCD.
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EMVCo
© 2011 austriamicrosystems
PICC to PCD
PICC signal shaping
For the communication from PICC to PCD, both Type A and Type B use load modulation. The carrier frequency fc is
used to derive a subcarrier with frequency fs equal to fc/16 (~847 kHz).
Switching a load on and off at this frequency creates the subcarrier. When the PICC is in the loaded state, a higher
current will flow through the antenna of the PICC than in the case where the load is not switched on. This difference in
current in the PICC antenna is sensed by the PCD.
Type A modulates the subcarrier using On-Off Keying (OOK).
Type B modulates the subcarrier using Binary Phase Shift
Keying (BPSK) .
BPSK uses two signal phases: 0 degrees and 180 degrees.
If the phase of the wave does not change with regard to a
reference phase, then the signal state stays the same (low or
high). If the phase of the wave changes by 180 degrees (i.e.
the phase reverses) then the signal state changes. The
reference phase is referred to as Ø0.
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EMVCo
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Mesaurement POINTS
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SIMULATIONS
Reference PICC PCD
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SIMULATIONS
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MW Studio
FEM solver
DS Studio
S-Parameter Analysis
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SIMULATIONS
PICC
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MW Studio
FEM solver
DS Studio
S-Parameter Analysis
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SIMULATIONS
PCD
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SIMULATION MODEL
VALIDATION
(vs. measurements)
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SYSTEM SIMULATIONS
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Simulation
sweep of distance D from 15mm to 45mm
sweep of input signal from 3Vpp to 5Vpp
different configuration PINs at J7 (1-2;1-3;1-4;1-5)
Hardware used during measurements:
- PAYPASS reference PICC Antenna (Version 2.1)
- Reference PCD (A01-088)
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SYSTEM SIMULATIONS
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CST MW Studio 3D model
D
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SYSTEM SIMULATIONS
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PCD PICC
Physical model (3DEM)
PCD circuitry
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Example of simulation results
DS TD-analysis
PICC circuitry
(w/o Modulation and external noise)
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SYSTEM SIMULATIONS
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NOTE:
15m: Measurements data at D = 15mm
15s: Simulation data at D = 15mm
…
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SYSTEM SIMULATIONS (RF Power Validation)
Measurements vs Simulation (@ differents PICC Setting)
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Example of simulated signal at the pick-up coil
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SYSETM SIMULATIONS (Example of Signal)
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REAL SYSTEM SIMULATIONS
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PCD to PICC Signal (Type A)
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REAL SYSTEM SIMULATIONS
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PCD to PICC Signal (Type B)
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REAL SYSTEM SIMULATIONS
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EMV contactless equivalent system model developed.
Good agreement between simulations and measurements in simulation of:
• RF power level
• Time domain behavior of the signal
Model can be used to optimize and fine tune any EMV Contactless system.
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CONCLUSION
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Reference Design
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Sim 2.5 V
Meas 2.7 V
Sim 4.9 V
Meas 5 V
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Reference Design
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Reference Design
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