Proximity Antenna Training for 13.56 MHz

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Philips Semiconductors

Proximity Antenna Training for 13.56 MHzProximity Antenna Training for 13.56 MHz

Directly matched Directly matched antennaantenna

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Directly matched antennaDirectly matched antenna

RC500RC400

(or other

Reader)EMC-Filter

Rx

Tx

Rx- Circuit

Mat

chin

gZ

=70

0

Antenna

Matching

Z=

700

Directly matched antenna

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3) Tuning

5) Finetuning

1) Matching

6) Receive Circuit

Requirements:

load impedance = 700!

1) Matching

2) Resonanceresonance at 13.56 MHz

2) Resonance

4) Q-factor quality factor 35

quality factor 100

4) Q-factor

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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

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Directly matched antennaDirectly matched antennaComplete antennaComplete antenna

AntennaCoil

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Directly matched antennaDirectly matched antennaAntenna coilAntenna coil

La

Lb

RCoil

RCoil

HnHLLL ba 2...300 HnHLLL ba 2...300

2...2.02 coilRR 2...2.02 coilRR @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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Directly matched antennaDirectly matched antennaAntenna coilAntenna 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

La

Lb

RCoil

RCoil

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Directly matched antennaDirectly matched antennaSimplificationSimplification

Due to the symmetrical circuitry of the whole antenna the antenna can be simplified:

ba LL ba LL

2ant

ba

ZZZ

2ant

ba

ZZZ

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Directly matched antennaDirectly matched antennaCalculate the external resistorCalculate the external resistor

CoilLext RQ

LRRR

22

1 CoilLext R

Q

LRRR

22

1

Consider the power consumption!

Q

LRL

MIFARE Q = 35

I*CODE Q = 100General:

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Directly matched antennaDirectly matched antennaCalculate the capacitorsCalculate the capacitors

2

2

22

2

2

2

11

1

1

CR

LCCL

CLRCC ba

2

2

22

2

2

2

11

1

1

CR

LCCL

CLRCC ba

aaa

ba

ZRL

ZRLR

ZRL

CC

111

1

222

222

aaa

ba

ZRL

ZRLR

ZRL

CC

111

1

222

222

350aZwith

Remark: there is an Excel-Sheet available, that supports this calculation.

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HnHLLL ba 2...300 HnHLLL ba 2...300

2...2.02 coilRR 2...2.02 coilRR

Directly matched antennaDirectly matched antennaEstimation: Startvalues for the tuningEstimation: Startvalues for the tuning

pFCC ba 2711 pFCC ba 2711

pFpFCC ba 600...10022 pFpFCC ba 600...10022

3...3.0extR 3...3.0extR 7.1...2.0extR 7.1...2.0extR

measured

calculated

00700 jant eZ

00700 jant eZ

1

2

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Directly matched antennaDirectly matched antennaTune resonance and impedanceTune resonance and impedance

Start

tune phase to 0° ± 10° with C2

decreaseC2

no

increaseC2

yesfres>13.56MHz ?possible ?

no

Tuning OK|Z|=Zant ± 10%

phase=0° ± 10°

no

yes

Z < Zant-10%?yes

Z >Zant+10% ?increase C1 yes

decrease C1

no

00700 jant eZ

00700 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

500

1000

1500

2000

1500

2000

2500

3000

350013.56 MHz

f [MHz]

|Zin| [] phase [deg.]

Zant

phase


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• Design a coil



•Connect antenna to the RC500•Tune again




Directly matched antennaDirectly matched antennaConnect Antenna to the RC500Connect Antenna to the RC500

Guideline:

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C1a

C1b

C2b

C2a

Matching Circuit

C

Antenna

La

Lb

R

R

distance increased ?

yes

no

no Cis added

yes

decrease C2

Find dmax

Add C C < 10 pF

Start

Find dmax

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

no

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PHILIPS

A

Channel A:500mV/DIV

Timebase:1µs/DIV

2.5µs

95%

Reader

send request command

Directly matched antennaDirectly matched antennaChecking the Q-FactorChecking the Q-Factor

“Antenna Loop”

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Directly matched antennaDirectly matched antennaRC500 Serial Signal SwitchRC500 Serial Signal Switch

Man

chester

Deco

der

SerialData

IN CarrierDemodulator Rx Pin 29

SubcarrierDemodulator

Serial Data OUT

Miller CoderEnvelope

Modulator Driver Tx

Digital Test Signal

0123

ModulatorSource Switch

7 6 5 4 3 2 1 0

MFoutSelect Switch

SubcarrierDemodulator

RFU

0 1

Mfin Pin3

Mfout Pin 4

Manchesterw. Subcarrier

Transmit NRZ

Envelope

0123

DecoderSource Switch

Manchester OUT

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time in msec

Pin 4 (3): Transmit NRZ 2V/Dev.

Pin 4 (2): Envelope2V/Dev.

RFOut 0.5V/Div.

RC500 test signals

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Directly matched antennaDirectly matched antennaCheckCheck

• Design a coil



•Connect antenna to the RC500•Tune resonance and impedance




Guideline:

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Reader

send request command

Directly matched antennaDirectly matched antennaCheck the cards answerCheck the cards answer

kR 2.21 kR 2.21

Startvalue:

Insert RX-CircuitryInsert RX-Circuitry

Check the card’s answer with oscilloscope (trigger on Pin 4, Envelope)

Check the card’s answer with oscilloscope (trigger on Pin 4, Envelope)

Get the max. operating distanceGet the max. operating distance

Check the received signal at the RC500 (Pin 4, Manchester)

Check the received signal at the RC500 (Pin 4, Manchester)

Adjust R1 (valid Manchester at min. and max operating distance)

Adjust R1 (valid Manchester at min. and max operating distance)

“Antenna-Loop”

Attention: Input voltage at Pin 29 (Rx) shall not exceed ± 1.5V!

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time in msec

Pin 4 (5): Manchester 2V/Dev.

Pin 4 (4): Manchester with Subcarrier2V/Dev.

RFOut 1V/Dev.

RC500 test signals

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6) Receive Circuit

2) Resonance3) Tuning4) Q-factor5) Finetuning

1) Matching • Design a coil



•Connect antenna to the RC500•Tune resonance and impedance




3) Tuning4) Q-factor5) Finetuning

6) Receive Circuit

Directly matched antennaDirectly matched antennaSummarySummary

Proximity Antenna Training for 13.56 MHz

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Transcript of Proximity Antenna Training for 13.56 MHz