M211_50-Ohm-Ant_V11_RBt -1 Philips Semiconductors 50 Ohm matched antenna Proximity Antenna Training...

M21

1_50

-Ohm

-Ant

_V11

_RB

t -1

Philips Semiconductors

50 Ohm matched 50 Ohm matched antennaantenna

Proximity Antenna Training for 13.56 MHzProximity Antenna Training for 13.56 MHz

M21

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-Ohm

-Ant

_V11

_RB

t -2


50 50 matched antenna matched antenna

RC500RC400

(or other

Reader)EMC-Filter

Rx

Tx

Rx- Circuit

Mat

chin

gZ

=50

Antenna

Matching

Z =

50

50 matched antenna

M21

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3) Tuning

5) Finetuning

1) Matching

6) Receive Circuit

Requirements:

load impedance = 50!

1) Matching

2) Resonanceresonance at 13.56 MHz

2) Resonance

4) Q-factor quality factor < 35

quality factor < 100

4) Q-factor

M21

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6) Receive Circuit

2) Resonance3) Tuning4) Q-factor5) Finetuning

1) Matching


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

3) Tuning4) Q-factor5) Finetuning

6) Receive Circuit

M21

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-Ohm

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50 50 matched antenna matched antennaDesign a coilDesign a coil

L

Rext

Rcoil

HnHLL ba 2...300 HnHLL ba 2...300

2...2.0coilR 2...2.0coilR @13.56 MHz!

L and R of the antenna coil shall be measured at 13.56 MHz (impedance analyser or L-C-R Meter).

8.1)/ln(][

][2.0 NDll

m

HL ba

8.1)/ln(

][

][2.0 NDll

m

HL ba

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 conductorN: number of turns: shape factor =1.07 for circular coils =1.54 for square coils

Estimation:

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50 50 matched antenna matched antennaDesign a coilDesign a coil

0 5 10 15 20

0.5

1

1.5

0 5 10 15 20

1

2

antenna radius [cm]

antenna radius [cm]

L [µH]

N

L

Rext

Rcoil

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50 50 matched antenna matched antennaCalculate the parallel capacitanceCalculate the parallel capacitance

CoilLext RQ

LRRR

CoilLext R

Q

LRRR

Consider the power consumption!

2

2

22

2

2

2

1

1

1

CR

LCCL

CLRC

2

2

22

2

2

2

1

1

1

CR

LCCL

CLRC

aaa ZRL

ZRLR

ZRL

C

111

1

222

22

aaa ZRL

ZRLR

ZRL

C

111

1

222

22

50Anta ZZwith

C2

L

Rcoil

C1

Zant

Rext

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50 50 matched antenna matched antennaTune resonance and impedanceTune resonance and impedance

Start

tune phase to 0° ± 10° with C2

possible ?

Z < Zant-10%?

Z >Zant+10% ?

fres>13.56MHz ?increase

C2

decreaseC2

increase C1

decrease C1

Tuning OK|Z|=Zant ± 10%

phase=0° ± 10°

yes

yes

yes

yes

no

no

no

no

0050 jant eZ

0050 jant eZ

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10 11 12 13 14 15 16 17 18 -100

-80

-60

-40

-20

0

20

40

60

80

0

200

400

600

800

1000

1200

1400

1600

180013.56 MHz

f [MHz]

|Zin| [] phase [deg.]

Zant

phase

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-Ohm

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0


• 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

50 50 matched antenna matched antennaConnect Antenna to the MF RC500Connect Antenna to the MF RC500

Guideline:

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1



distance increased ?

no Cis added

Find max. distance

yes

yes

no

Add C C < 10 pF

Start

decrease C2

remove C add 2* C to C2aadd 2* C to C2b

no

Find dmax

C2

Lant

Rant

C1

Zant

Rext

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9


50 50 matched antenna matched antennaBalunBalun

I

I

+U

-U

50

Balun (balanced - unbalanced)Balun (balanced - unbalanced)

The same as directly matched antenna...

M21

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0


I

I

50 50 matched antenna matched antennaCompensated antennaCompensated antenna

I

I

50 50

M21

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1


50 50 matched antenna matched antennaPrinciple of the compensated antennaPrinciple of the compensated antenna

without compensation

with compensation

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2


L = 450nHR = 0.3

50 50 matched antenna matched antennaExample: Circular antennaExample: Circular antenna

M21

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3


L = 700nHR = 0.3

50 50 matched antenna matched antennaExample: Square antennaExample: Square antenna

M211_50-Ohm-Ant_V11_RBt -1 Philips Semiconductors 50 Ohm matched antenna Proximity Antenna Training...

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