Matching circuit in the case of differential antenna with twisted pair cable

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Matching circuit in the case of differential antenna with twisted pair cable

Contributor I


Working on a RFID project that would involve a PN5180 and an external, off pcb, antenna connected with some twisted pair cable (distance is around 1m). Power is not a problem : the system isn't on battery, and the more range the better. I'm using a differential antenna topology and i'm trying to use the "matching antennas.xls" tool provided by NXP. That brings me to the following picture :


Let's say the twisted pair has a characteristic impedance of 50 Ohms and the antenna already has its own matching circuit on the antenna pcb to accomodate for that.

Now, how should i use the excel tool ? Because it seems to adress only the case of antenna next-to the transceiver. How do i need to understand the following sentences taken from the documentation on the PN5180 :

"the antenna impedance is tuned to Z ≈ 20Ω"


"Note: The antenna impedance tuning and measurement must be done with R = 10Ω
between ANT1 and ANT2."

(both from AN11744 - page 9/45).

Would there be an advantage to redesign the antenna pcb to change its matching circuit and the type of cable to accomodate for what the PN5180 needs ?

Thank you in advance

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NXP TechSupport
NXP TechSupport

Hello @bastiaens 

Thanks for contacting us and say sorry for the late to response.

For your questions, it's recommended that you follow this application notes AN11740 - PN5180 antenna design, which will give you the answers what you want. Please check the attachment.

Please feel free to contact us if any questions.

Best Regards,


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