NFC Forum Measurements 1 Objective Suite of standard

NFC Forum Measurements 1

Objective • Suite of standard tests to qualify Readers and Tags – Ensure Interoperability – Present discussion limited to certain aspects of ‘Analog Specifications’ only • RF Power and Signal Interface 2

Accessories defined by NFC Forum – Reference Polling Devices (i. e. Reader) • Used to characterize Tags – Reference Listening Devices (i. e. Tag) • Used to characterize Readers 3

NFC Forum Reference Polling Devices PD 0 72 mm f antenna 4 T uncompensated/compensated PD 3 47 X 38 mm antenna 4 T uncompensated/compensated PD 6 25 X 20 mm antenna 4 T uncompensated/compensated 4

Reference Polling Device - Simplified Schematic J 1 C 1 L 1 Antenna Device C 2 C 1 PD-0 103 67 PD-3 208 76 PD-6 485 115 C 2 J 2 ~1 W Nominal cap p. F Antenna: Uncompensated mode standard. Compensated mode possible J 1: RF (13. 56 MHz) excitation J 2: Monitor antenna current (e. g. Load modulation) C 1, C 2 used to match to 50 ohm at J 1 5

Thevenize and R-C transformation C 1 ≈ (C 1+C 2) ≈C 1 R 0 ≡ C 2 ≡ <R 0 C 2 Alternative Methods • Smith Chart • Analytically 6

Example: PD-3 is matched to 50 W C 1, C 2 match 50 W to ~ [C 1/(C 1+C 2)]2. 50 W = 3. 6 W (3. 4 W by exact calculation) Therefore, Coil resistance = 3. 6 – 1 = 2. 6 W Reactance at 13. 56 MHz = 1/(w. (208+76)p. F) = 41. 3 W Therefore, Q of inductor (same reactance as capacitor at resonance) = 41. 3/2. 6 = 15. 9 And inductance = 485 n. H (494. 5 n. H by exact calculation) 7

NFC Forum Reference Listening Devices LD 1 72 X 42 mm 4 T LD 3 47 X 32 mm 5 T LD 6 25 X 20 mm 5 T All antennas are uncompensated 8

Reference Listening Device - Simplified Schematic J 1 J 5 Detected output J 2 Load modulation Used for: Qualifying Readers Calibrating specified magnetic field generated by NFC Forum Polling Devices 9

Setting up Specified Magnetic Field Example – Setting PD-3 up for specified magnetic field • LD-1 is placed at 5 mm from PD-3 • RF excitation is adjusted to PD-3 (J 1) till detected output from LD-1 (at J 1) is 4. 72 V. This sets up for the ‘nominal’ field. • For ‘minimum’ field detected output should be 4. 24 V • For ‘maximum’ field detected output should be 2. 22 V using LD-3 instead of LD-1 • Nominal field = 7. 3 A/m from independent measurements RF Sig Gen J 1 PD-3 LD-1 J 1 10

Magnetic Field from Readers 11

Example: Tag-talk-first (TTF) Tag Testing TTF Tag under test RF Signal Generator (13. 56 MHz) J 1 J 2 TTF does not require query command e. g. SENS_REQ Voltage doubling rectifier 20 Ms/s PCI Bus PC with DAS Software PD-X Set up specified magnetic field for a particular NFC Forum test using LD-X Replace LD-X by Tag Under Test and perform tests Analysis of received frames done in software Detect logic level Manchester decoding CRC check 12

DAS Waveforms 13

Examples of some NFC Forum Tests 14

Tag ‘Functioning Properly’ Objective: How the Tag functions in a specified field generated by a given Polling Device? Pass criterion: Return serial ID and CRC correctly for three independent frames TTF Tag under test RF Signal Generator (13. 56 MHz) J 1 J 2 Voltage doubling rectifier 20 Ms/s PCI Bus PC with DAS Software PD-X 15

Nominal NFC Field: Field according to settings specified by NFC Forum Tag 1, Tag 2: Minimum field at which test Tags ‘function correctly’ 16

Influence of Tag on Operating Field (Loading) Objective: Tag loading on the Reader should be within specified limits Tag under test RF Signal Generator J 1 J 2 Oscilloscope PD-X Pass criterion: Change in RF voltage at J 2 (i. e. Reader antenna current) cannot exceed specified value for Tag at a certain distance e. g. 0. 3 V for PD-3 set up for minimum magnetic field and test Tag placed at 5 mm 17

Loading test - continued Loading occurs due to the ‘Choking’ effect of parallel resonance Strong coupling phenomenon I 1 Vi ~ R 1 C 1 L 1 -M ~1/w 02. M M +jw. M ~w 02. M 2/R 2 -jw. M (w 0. M)/R 2>>1 18

Tag Requirement for Carrier Frequency Objective: Tag should ‘function properly’ for 13. 55 to 13. 57 MHz Pass Criterion : Return serial ID and CRC correctly for three independent frames TTF Tag under test RF Signal Generator (13. 56 MHz) J 1 J 2 Voltage doubling rectifier 20 Ms/s PCI Bus PC with DAS Software PD-X 19

Tag Requirement for Power-On Objective: Tag should respond within specified time after field is applied Tag under test RF Signal Generator J 1 J 2 AM In Scope Sync PD-X Pulse Generator 20

Pulsed RF Waveform – can be used for query commands also 21

Tag Requirement for Load Modulation Objective: Load modulation to be maintained within specified limits Tag under test RF Signal Generator J 1 J 2 Oscilloscope PD-X Magnetic field set up for nominal value. Pass Criterion: Signal at J 2 should have a subcarrier = fc/16 (847. 5 KHz) and specified P-P amplitude (Vpp) of the load modulation, e. g. between 9. 5 and 53 m. V for PD-3 22

Signal at J 2 23

Thank You! 24