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Proximity Antenna Training for 13.56 MHz

Proximity Antenna Training for 13.56 MHz. 50 Ohm matched antenna. 50  matched antenna. Matching. Antenna. Z = 50 . 50  matched antenna. RC500 RC400 (or other Reader). Rx. Rx- Circuit. Tx. Matching. Z=50 . EMC- Filter. !. load impedance = 50. 1) Matching.

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Proximity Antenna Training for 13.56 MHz

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  1. Proximity Antenna Training for 13.56 MHz 50 Ohm matched antenna

  2. 50  matched antenna Matching Antenna Z = 50 50  matched antenna RC500 RC400 (or other Reader) Rx Rx- Circuit Tx Matching Z=50 EMC- Filter

  3. ! load impedance = 50 1) Matching 1) Matching 2) Resonance resonance at 13.56 MHz 4) Q-factor quality factor < 35 quality factor < 100 6) Receive Circuit 50  matched antenna Requirements: 2) Resonance 3) Tuning 4) Q-factor 5) Finetuning

  4. 3) Tuning 4) Q-factor 5) Finetuning 6) Receive Circuit 50  matched antenna Guideline: 1) Matching • Design a coil • Calculate the parallel capacitance • Tune resonance and impedance • Connect antenna to the RC500 • Tune again • Check (and adjust) the Q-factor • Finetune resonance and impedance • Find the values for Rx-circuit 2) Resonance 3) Tuning 4) Q-factor 5) Finetuning 6) Receive Circuit

  5. Rext Rcoil Estimation: L La+b = L: coil inductance l: length of the conductor circular: l = 2**r (r=coil radius) square l = 4*a (a lateral length) d: diameter of the conductor N: number of turns : shape factor  =1.07 for circular coils =1.54 for square coils 50  matched antenna Design a coil L and R of the antenna coil shall be measured at 13.56 MHz (impedance analyser or L-C-R Meter). @13.56 MHz!

  6. Rext 1.5 Rcoil L [µH] 1 0.5 L 0 5 10 15 20 antenna radius [cm] 2 N 1 0 5 10 15 20 antenna radius [cm] 50  matched antenna Design a coil

  7. Consider the power consumption! C1 Rext Rcoil Zant C2 L with 50  matched antenna Calculate the parallel capacitance

  8. 50  matched antenna Tune resonance and impedance Start tune phase to 0° ± 10° with C2 possible ? fres>13.56MHz ? increase C2 no yes yes no decrease C2 Z < Zant-10%? yes decrease C1 no Tuning OK |Z|=Zant ± 10% phase=0° ± 10° Z >Zant+10% ? yes no increase C1

  9. 80 1800 13.56 MHz 60 1600 40 1400 20 1200 0 1000 |Zin| [] phase [deg.] -20 800 -40 600 Zant -60 400 -80 200 phase -100 0 10 11 12 13 14 15 16 17 18 f [MHz] 50  matched antenna Tune resonance and impedance

  10. 50  matched antenna Connect Antenna to the MF RC500 Guideline: • Design a coil • Calculate the parallel capacitance • Tune resonance and impedance • Connect antenna to the RC500 • Tune again • Check (and adjust) the Q-factor • Finetune resonance and impedance • Find the values for Rx-circuit

  11. Start Find dmax Add C C < 10 pF Find max. distance distance increased ? C1 yes Rext decrease C2 no Rant Zant no C is added yes C2 Lant no remove C add 2* C to C2a add 2* C to C2b 50  matched antenna Tune resonance and impedance

  12. 50  matched antenna Balun I The same as directly matched antenna... +U 50  -U I Balun (balanced - unbalanced)

  13. I I 50  matched antenna Compensated antenna I 50  50  I

  14. without compensation with compensation 50  matched antenna Principle of the compensated antenna

  15. 50  matched antenna Example: Circular antenna L = 450nH R = 0.3 

  16. 50  matched antenna Example: Square antenna L = 700nH R = 0.3 

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