PN5180 external antenna

[oferrer]

Thanks to NXP documentation, community support, and antenna design tool, I have developed an ISO15693 RFID reader device using a PN5180, customizing both the antenna dimensions and the matching and filter circuit components to meet the application requirements (three sample devices below).

Due to new requirements, the device will no longer be handheld but will be fixed under a surface. I need then, with the same dimensions of the antenna, to move the reading point about 30cm away from the control but on the same surface. That is, I need to separate the reader from the antenna.

Any guide on how to do it, which part of the circuit is in the reader and which part goes to the antenna. I need to change the matching circuit if it will only be about 30cm away. What cable and connector should I use.

Thanks in advance, Osmany

[jimmychan]

You could separate the antenna coil from your circuit. The cable in between antenna coil and the circuit is better use the coaxial cable. Then the matching circuit need to tune again base on your changes.

[oferrer]

Thanks @jimmychan for your reply,
But, does any component from matching circuit have to be moved to the end of the cable where the coil will be? Is there a tool to estimate how a 30cm long 50ohm coaxial cable affects the LCR values ​​of the coil?

Best regards,

Osmany

[jimmychan]

Antenna coil can be separated and then is the 30cm cable. The matching circuit can be put on the pcb side.  We have an App. Note talk about the Antenna design and using VNA for the matching measurement (AN11740). 

FYI. A cheaper solution to instead of using high end impedance analyzer (How to use the NanoVNA for the NFC reader antenna design). 

[oferrer]

How SMA is connected to TX1/RXP  and RXN/TX2 wires?

[jimmychan]

Sorry, I don't understand what is your question? 

[oferrer]

Hi @jimmychan 

I apologize for not having explained myself well.

The pn5180 receiver works with differential RXP/RXN input signals. Therefore, one end of the antenna is connected to RXP and the other to RXN. The same happens with the transmitter.

If I use a coaxial cable to connect the coil to the circuitry, using an SMA connector, how would the connection be? I should not use a shielded twisted pair instead.

I kindly thank you for your attention,

Osmany

[jimmychan]

You could test different cables to check the performance on your circuit base on your design.