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TRF7963A: TRF7963

Dmitry Moonin
Prodigy 50 points
Part Number: TRF7963A
Other Parts Discussed in Thread: TRF7960

I'm new in RFID and I need some advice in design of RFID PCB Antenna and the RFID Tag.
I plan to use reference design based on TRF7963A and it will read ISO14443A tags in short distance (up to 1cm).

Each antenna will have its matching circuit and then will be connected to the TRF7693A reader through RF Switch in order to avoid cross talking between them.
The board should have a shape of 7 hexagons connected together(6 by the circle and 1 in center), each hexagon should have a PCB round antennas.On top layer, around or inside of antenna LEDs will be populated (6 LEDs by the circle and 1 in the center). All electronics components at the same board.

Please help me to understand my steps to achieve that:

1. Estimate PCB antenna parameters: inductance, diameter, number of loops, trice width, trace to trace distance in some simulation program.

2. Create the PCB with an estimated dimension of an antenna.

3. Measure the actual impedance with Network Analyzer and calculate value for capacitors and resistors for the matching circuit for each antenna by using Smith Chart Simulation Program.

I will appreciate any help.

Thanks.

Dmitry.

  • 0
    TI__Guru*** 135355 points

    Hello Dmitry,

    We have a detailed app note which covers these points and includes a tool which will estimate PCB antenna parameters for FR4 PCBs: http://www.ti.com/lit/pdf/sloa241

  • 0 in reply to Ralph Jacobi
    Prodigy 50 points
    Hello Ralph,
    Thank you for your quick response.
    I've tried to run that tool in my computer, it give me an error that file "Tabctl32.ocx" is missing or invilid. I'm using Win 10.
    How can I fix it in order to run the tool?
    Thanks
  • 0 in reply to Dmitry Moonin
    TI__Guru*** 135355 points

    Hi Dmitry,

    Ahh, I'm sorry to hear you are Windows 10... I have yet to figure out how to run it on Windows 10 myself. It was a tool created a long time ago and no source code exists for it so it's not something updateable.

    Another tool I know of is this one: http://emclab.mst.edu/inductance/

    Edit: Should've mentioned but it works on Win 7 and as far as I know Win 8/8/1 as well, so you could always try a PC running one of those OS's

  • 0 in reply to Ralph Jacobi
    Prodigy 50 points

    Hi Ralph,

    I'm just following  document SLOA135A - "Antenna Matching for the TRF7960 RFID Reader".

    On the page 3 it says to perform calibration for the network analyzer by connecting a RF test connector with 50 load, short and open.

    Does it mean I have to be connected to the antenna on my board via RF coax connector and perform calibration or it means calibrate the Network Analyzer itself and then connect to the board?

    Thank you.

  • 0 in reply to Dmitry Moonin
    TI__Guru*** 135355 points
    Hi Dmitry,

    The latter. The Network Analyzer needs to be calibrated with a cal-kit before attaching to the board. That said if you will be using some length of Coax cabling between the antenna and the Network analyzer, you may want to calibrate from the end of the cabling so you can calibrate out any parasitics introduced by it.
  • 0 in reply to Ralph Jacobi
    Prodigy 50 points

    Tank you for quick response Ralph,

    That what I know from my experience working with Network Analyzer, I just was a little confused.

    When I attach to the board via RF test board near to the PCB antenna, 0 Ohm resistor between antenna and reader, should be removed, in order to be connected only to the antenna and measure its impedance and inductance?

    There is capacitor C23 in series (reference design), does 0 Ohm resistor instead have to be installed in order to perform measurement and latter to put capacitor with calculated value by Smith Chart?

    Could it be an another matching network, I mean various combination of components, such as Inductors, Resistors and Capacitors?

    Thank you.

  • 0 in reply to Dmitry Moonin
    TI__Guru*** 135355 points
    Hello Dmitry,

    All of that sounds correct. You need to remove the 0 ohm to isolate the antenna, and yes where there is the series cap there needs to be a zero ohm to allow the antenna inductance to be measured and then replaced with the calculated capacitor value.
  • 0 in reply to Ralph Jacobi
    Prodigy 50 points

    Hello Ralph,

    In my project I can not avoid using metal around NFC antenna, in fact I have a pretty big Li-Po battery is sitting underneath of the board and a distance between them is 1 mm.

    Thus I have 7 NFC antennas on the board and battery crosses 5 of them.

    Might a flexible Ferrite Sheet 13.56MHz between be a solution for that issue?

    Thank you.

  • 0 in reply to Dmitry Moonin
    TI__Guru*** 135355 points
    Hi Dmitry,

    A ferrite sheet would certainly be helpful. It won't eliminate the impact but it will help minimize it. You'll want to do the tuning with both the battery and ferrite sheet in place. Fortunately since you are only trying to get ~1cm read range, such a system should be quite feasible.