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NFC Forum Measurements 1 Objective Suite of standard tests to qualify Readers and Tags –Ensure Interoperability –Present discussion limited to certain.

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Presentation on theme: "NFC Forum Measurements 1 Objective Suite of standard tests to qualify Readers and Tags –Ensure Interoperability –Present discussion limited to certain."— Presentation transcript:

1

2 NFC Forum Measurements 1

3 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

4 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

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

6 Reference Polling Device - Simplified Schematic J1 J2  L1 C2 Antenna 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 C1 DeviceNominal cap pF C2C1 PD PD PD

7 6 C2 C1 ≡ ≈C1 C2 R0 Alternative Methods Smith Chart Analytically

8 Example: PD-3 is matched to 50  C1, C2 match 50  to ~ [C1/(C1+C2)] 2.50  = 3.6  (3.4  by exact calculation) Therefore, Coil resistance = 3.6 – 1 = 2.6  Reactance at MHz = 1/( .(208+76)pF) = 41.3  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) 7

9 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 8

10 Reference Listening Device - Simplified Schematic J5 J2 J1 Used for: Qualifying Readers Calibrating specified magnetic field generated by NFC Forum Polling Devices Detected output Load modulation 9

11 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 10 RF Sig Gen PD-3 LD-1 J1

12 Magnetic Field from Readers 11

13 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 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 TTF does not require query command e.g. SENS_REQ 12

14 13 DAS Waveforms

15 Examples of some NFC Forum Tests 14

16 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 15

17 Nominal NFC Field: Field according to settings specified by NFC Forum Tag1,Tag2: Minimum field at which test Tags ‘function correctly’ 16

18 Influence of Tag on Operating Field (Loading) Objective: Tag loading on the Reader should be within specified limits J2 RF Signal Generator J1 PD-X Oscilloscope Tag under test 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 17

19 Loading test - continued Loading occurs due to the ‘Choking’ effect of parallel resonance Strong coupling phenomenon I1I1 R1 L1-M ViVi ~ C1 M ~1/  0 2.M ~  0 2.M 2 /R2 (  0.M)/R2>>1 +j .M -j .M 18

20 Tag Requirement for Carrier Frequency Objective: Tag should ‘function properly’ for to 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 19

21 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 20

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

23 Tag Requirement for Load Modulation Objective: Load modulation to be maintained within specified limits J2 RF Signal Generator J1 PD-X Oscilloscope Tag under test 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 22

24 Signal at J2 23

25 Thank You! 24


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