RF Amplifier for PN532

[feiyan]

I am testing the RF amplifier on a PN532 breakout board for a better reading distance as discussed in AN1425. Finally I want to identify the tiny 2* 12 glass tag with PN532 chip.

I use this PN532 board(https://www.adafruit.com/product/364 ). Its matching circuit matches with its antenna very well.

Without any amplifier, the reading distance is about 10cm for a  85mm*54mm rfid card and about 1.5cm for this tiny glass tag.

After adding the amplifier into this breakout board, the big card distance decreases to less than 5CM, the glass tag can not be identified. The values of amplifier components are from Table 6 in the AN1425 document. I did not change other components in the breakout board.

So I want to know,

(1)After adding this amplifier circuit, I need to do the antenna matching task again?

(2)"The PN5xx has two transceiver pin: TX1 and TX2. By using the amplifier solution, the contactless reader transmission mode should be switched to asynchronous mode. This is done by setting the register 0x14(TXControlReg) to 0x83".

This is from Page 7 of the AN1425 document.

For the PN532 chip, how can I switch to asynchronous mode? I can not find the TXControlReg register in its datasheet and user manual.

Appreciate for any other good suggestion.

Thank you

Fei

[feiyan]

Hi,

Could you give me some suggestion about this PN532 problem?

Fei

[Jorge_Gonzalez]

Hello Fei Yan:

Let me replicate here the answers to the support case you submitted:

1) Yes, the antenna matching should be recalculated after adding the amplifier. There is an excel file which aims in this procedure included in the AN1425 zip file:

http://cache.nxp.com/documents/application_note/AN1425_AN166510.zip

2) The register is called CIU_TxControl in the PN532. The bit fields are compatible with the description in the appnote.

Best regards!
Jorge Gonzalez

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[feiyan]

Hello, Jorge,

Thank you for your reply.

I have other questions about PN532 amplifier.

(1) About the antenna matching. Before adding the amplifier into the PN532 breakout board, the matching task is done. And the amplifier circuit is on the left of the matching circuit and the RF antenna. So if the antenna is not changed, I should do a new antenna matching only for adding the amplifier?

(2) Now in the amplifier test, the amplifier components are in a small board(it is not the PN532 breakout board), then I use some wires to connect these two boards together. Of course these wires are as shorter as possible. This can be a problem or not? I need produce a new board for this test? DO you have any NFC evaluation board with amplifier for sale?

(3) According to AN11038, I use the oscilloscope to measure some important signals. But they are different with the pictures in the AN11038 document.

https://drive.google.com/open?id=0B-xiz9I2tKtKN1V3M2d0WmptQk0​

Can you find any problems from these pictures? The Txcontrol register is not correctly written with 0x83? or any other error?

Thank you very much

Fei