NFC Forum Measurements

Suite of standard tests to qualify Readers and Tags 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

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

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

Reference Polling Device - Simplified Schematic J1 Antenna L1 Device Nominal cap pF C2 C1 PD-0 103 67 PD-3 208 76 PD-6 485 115 C2 J2 ~1 W Antenna: Uncompensated mode standard. Compensated mode possible J1: RF (13.56 MHz) excitation J2: Monitor antenna current (e.g. Load modulation) C1,C2 used to match to 50 ohm at J1

Thevenize and R-C transformation ≡ ≡ Alternative Methods Smith Chart ≈ (C1+C2) ≈C1 R0 ≡ ≡ <R0 C2 C2 Alternative Methods Smith Chart Analytically

Example: PD-3 is matched to 50W C1, C2 match 50W to ~ [C1/(C1+C2)]2.50W = 3.6W (3.4W by exact calculation) Therefore, Coil resistance = 3.6 – 1 = 2.6W Reactance at 13.56 MHz = 1/(w.(208+76)pF) = 41.3W Therefore, Q of inductor (same reactance as capacitor at resonance) = 41.3/2.6 = 15.9 And inductance = 485 nH (494.5nH by exact calculation)

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

Reference Listening Device - Simplified Schematic J1 Detected output J5 J2 Load modulation Used for: Qualifying Readers Calibrating specified magnetic field generated by NFC Forum Polling Devices

Setting up Specified Magnetic Field Example – Setting PD-3 up for specified magnetic field LD-1 is placed at 5mm from PD-3 RF excitation is adjusted to PD-3 (J1) till detected output from LD-1 (at J1) 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 J1 RF Sig Gen PD-3 LD-1 J1

Magnetic Field from Readers

Example: Tag-talk-first (TTF) Tag Testing J2 RF Signal Generator (13.56 MHz) J1 PD-X Voltage doubling rectifier 20 Ms/s DAS PC with Software PCI Bus TTF Tag under test TTF does not require query command e.g. SENS_REQ 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

DAS Waveforms

Examples of some NFC Forum Tests

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 J2 RF Signal Generator (13.56 MHz) J1 PD-X Voltage doubling rectifier 20 Ms/s DAS PC with Software PCI Bus TTF Tag under test

Nominal NFC Field: Field according to settings specified by NFC Forum Tag1,Tag2: Minimum field at which test Tags ‘function correctly’

Influence of Tag on Operating Field (Loading) Objective: Tag loading on the Reader should be within specified limits Tag under test RF Signal Generator J1 Oscilloscope J2 PD-X Pass criterion: Change in RF voltage at J2 (i.e. Reader antenna current) cannot exceed specified value for Tag at a certain distance e.g. 0.3V for PD-3 set up for minimum magnetic field and test Tag placed at 5mm

Loading test - continued Loading occurs due to the ‘Choking’ effect of parallel resonance Strong coupling phenomenon I1 R1 L1-M Vi ~ C1 M ~1/w02.M ~w02.M2/R2 (w0.M)/R2>>1 +jw.M -jw.M

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 J2 RF Signal Generator (13.56 MHz) J1 PD-X Voltage doubling rectifier 20 Ms/s DAS PC with Software PCI Bus TTF Tag under test

Tag Requirement for Power-On Objective: Tag should respond within specified time after field is applied J2 RF Signal Generator J1 PD-X Scope Pulse Generator AM In Sync Tag under test

Pulsed RF Waveform – can be used for query commands also

Tag Requirement for Load Modulation Objective: Load modulation to be maintained within specified limits Tag under test RF Signal Generator J1 J2 Oscilloscope PD-X Magnetic field set up for nominal value. Pass Criterion: Signal at J2 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 mV for PD-3

Signal at J2

Thank You!