Near Field Communications (NFC) Technology & Measurements


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Near Field Communications (NFC) is an evolution of contactless data exchange which is being employed in mobile phone applications for data exchange and payment processing, among other applications. This presentation covers the evolution and technical details of this communications protocol along with compliance testing requirements.

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Near Field Communications (NFC) Technology & Measurements

  1. 1. NFC Technology and ConformanceTesting
  2. 2. Agendal NFC Basicsl Standard Evolutionl Physical Layer Compliance Tests 2
  3. 3. NFC Introductionl Contactless data exchange l Passive – active l Active – activel Close proximity ~ 10 cml Data transfer using the “near field” l Low carrier frequency of 13.56 MHz l Magnetic coupling between transmitter and receiver similar to transformer principlel Standard developed jointly by NXP and Sonyl Backward compatible with smart card technology l ISO/IEC 14443 A/B l JIS X 6319-4 3
  4. 4. NFC Coupling Method Information is coupled between the polling and listening devices using the near field – equivalent to transformer principle 4
  5. 5. Frequency Spectrum of NFC Signall Auxiliary carriers transfer information from passive listener (target) to poller (initiator) through load modulation on poller antennal Auxiliary carriers are not used in peer to peer communicationl Carrier is used as a power source in active-passive communications 5
  6. 6. Modulation Typesl Poller (initiator) uses ASK modulation on 13.56 MHz carrierl Passive devices communicate on auxiliary carrier via load modulation l ASK for 14443A and PSK for 14443B l ASK directly on carrier for JIS X 6319-4 6
  7. 7. Coding Types Used in NFCl NRZ-L: logical 1 and 0 coded as high and low level and signal level is maintained throughout a bit periodl Manchester: first half bit is high for a logical 1 and second half is high for logical 0l Modified Miller: negative going pulse after half a bit interval for a 1 and at the start of a bit interval for a 0. For a 1 followed by a zero, no pulse 7
  8. 8. Frequency and Time Representation 8
  9. 9. Evolution of NFC Air Interface 9
  10. 10. NFC Operating Modes Each mode can Use any of 3 technologiesl Card emulation mode (passive mode): behaves like existing contactless card and conforms to one of the legacy standardsl Peer to Peer mode: both devices are active and exchange datal Reader/Writer mode (active mode): the NFC device is active and reads or writes a passive legacy RFID tag 10
  11. 11. Poll Mode Resolution 11
  12. 12. NFC Standards Overview 12
  13. 13. NFC Tag Types 13
  14. 14. NFC RF Measurements – Listening Devicel NFC Forum Reference Polling Device l Sends commands to listening device l Received response from listening device (load modulation)l Command generator – modulated 13.56 MHz carrierl Load modulation measuring tool – oscilloscope or signal anlyzer 14
  15. 15. NFC RF Measurements – Polling Devicel NFC Forum reference listening device l Receives polling signal from device under test l Transmits appropriate response via load modulationl Listening device response generator – arbitrary waveform generator (AWG)l Measuring waveform tool – analyzes the polling signal and generates a trigger for the response generatorl Measuring Field tool – measures the carrier power from the poller 15
  16. 16. NFC Reference Polling and Listening Devices 16
  17. 17. RF Tests for NFC Devices in Polling Model Carrier frequency accuracyl Power level measurement l Sufficient power to drive passive devices l Measured within the specified volume above the coupling devicel Waveform characteristics l Rise time, fall time, etc.l Load modulation sensitivity l Correct reception at minimum specified levell Threshold level test l Polling device must switch off its RF field when exposed to an RF field f a certain strength 17
  18. 18. RF Tests for NFC Devices in Listening Model Load modulation measurement l The signal strength of the load modulation must be within required limitsl Power reception l The listening device must answer correctly even in bad conditionsl Frame delay time l Response time from the end of the polling command to the start of transmission from the phone in card emulation mode l Important in NFC-A mode for anti-collision 18
  19. 19. Test Setup for Polling Mode 19
  20. 20. Test Setup for Listening Mode 20
  21. 21. Carrier Power and Frequency Measurement 21
  22. 22. Load Modulation Load modulation Polling command 22
  23. 23. Automated Measurement Software 23
  24. 24. Poller Timing Values 24
  25. 25. Poller Signal vs. Time 25
  26. 26. Listener Values 26
  27. 27. Listener Signal vs. Time 27
  28. 28. Summaryl NFC technology is an evolution of contactless data exchange l Addition of peer to peer and read/write to passive smart card mode l Backward compatible with legacy smart cardl The NFC forum has established both RF and protocol compliance tests l Guarantees interoperabilityl RF testing verifies the air interface for polling and listening devices l Reference poller and listener l Command and response generator (AWG and vector signal generator) l Waveform analysis tool (oscilloscope with NFC trigger and I/Q demodulation) l Automation software controls acquisition and analyzes waveform data 28
  29. 29. Contact UsAbout Rohde & SchwarzRohde & Schwarz is an independent group of companies specializing in electronics. It is a leading supplier of solutions inthe fields of test and measurement, broadcasting, radiomonitoring and radiolocation, as well as secure communications.Established more than 75 years ago, Rohde & Schwarz has a global presence and a dedicated service network in over 70countries. Company headquarters are in Munich, Germany.Europe, Africa, Middle East+49 89 4129 12345customersupport@rohde-schwarz.comNorth America1-888-TEST-RSA (1-888-837-8772) 65 13 04 29