Designing antenna for NXP ICs

[viral8387]

Hi guys,

I am recently start working on MFRC522, I want to know that will MFRC522 give read-write range more than 7cms?

I am also struggling for antenna design. Please anyone can guide me to design antenna for NXP ICs.


Regards
Viral Chavda

 

[FvM]

mifare coil

The Pegoda reader (a NXP reference hardware) typically achieves 10 cm range with a circular coil of about 10 cm diameter. Larger ranges should be possible with larger coils, possibly a power amplification may be required. The reader should be designed in a way, that the specified ISO 14443 field strength of 1.5 - 7.5 A/m is achieved within the intended operation volume.

All NXP designs are using a resonant coil interface network as shown in the MFRC522 data sheet. It's properties can be analyzed by basic network equations or modelled with analog simulators.

NXP is also providing application notes under a NDA agreement.

 

[viral8387]

interfacing antenna with mfrc522

The Pegoda reader (a NXP reference hardware) typically achieves 10 cm range with a circular coil of about 10 cm diameter. Larger ranges should be possible with larger coils, possibly a power amplification may be required. The reader should be designed in a way, that the specified ISO 14443 field strength of 1.5 - 7.5 A/m is achieved within the intended operation volume.

All NXP designs are using a resonant coil interface network as shown in the MFRC522 data sheet. It's properties can be analyzed by basic network equations or modelled with analog simulators.

NXP is also providing application notes under a NDA agreement.

Hi
Thanks for your valuable reply.....
I have documents of nxp for antanna design. I have designed one board with CLRC632 with square antanna of 2 turns having wire diameter 1mm , wire spacing 0.5mm (50mmx48mm). Now the problem occur that i am not able to tune that board using that document. Can you guide me to tune it?
EMC filter , RX and Vmid section is same as mentioned in NXP documents.


VMID---------- 820E-----
| |
| |
100n |
| |
GND |
RX----------------------------560E--1n--
|
|
Tx1-----1uH-----------------------------------
|
68pF
|
GND-------------------------------------------
|
68pF
|
Tx2-----1uH-----------------------------------


Regards
Viral Chavda

 

[FvM]

mfrc522 tx2

Both parallel capacitor pairs have to be tuned while the series capacitors are setting the impedance transformation ratio. 68 pF surely isn't correct, it's 2 x 68 pF each in the NXP application note.

In my opinion, a 50 mm coil should rather have 4 than 2 turns, and it's not suited for distances above 50 or maximal 70 mm anyway, even if perfectly tuned.

 

[viral8387]

mfrc522 antenna design

Both parallel capacitor pairs have to be tuned while the series capacitors are setting the impedance transformation ratio. 68 pF surely isn't correct, it's 2 x 68 pF each in the NXP application note.

In my opinion, a 50 mm coil should rather have 4 than 2 turns, and it's not suited for distances above 50 or maximal 70 mm anyway, even if perfectly tuned.

Previously i had design antenna with 4 turn but its inductance are getting more than NXP recommendation and also i face difficulty while i am tuning it so i change turns from 4 to 2. As you told should i put two parallel capacitor in EMC filter of 68pF. m i right?



I m following this circuit for antanna matching circuit design.

 

[FvM]

mifare field strength

I think, it can work with 2 to 4 turns; I don't know wich variant will achieve higher field strength, the tuning (C1/C2) has to be different of course. C0 is 2*68 pF in the NXP reference design.