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TRF7970AEVM: Simple two advice requests for TRF7970A EVM Peer-to-Peer antenna

seokbong kang
Prodigy 40 points

Part Number: TRF7970AEVM

My two advice requests about TRF7970A EVM NFC Peer-to-Peer communication antenna are very simple.

 

1. What size to be taken for P-t-P test on belows( select 1 or 2 or many)?

① Pulse W7002 94.6x56.8x0.14 coil(L=0.65uH, R=0.95Ω, Q=57, Matched Q = 5~30)

② ABRACON ANFCA-6040-A02(F-PCB 60x40mm, 4turn, L=1.9+-10%)

③ Taoglas FXR.01.07.0100C.A(53.3x36.8mm, return loss >10dB)

④ ABRACON ANFCA-5035-A01(50x35. L=2.6+10% uH, R= 1.3+20%)

⑤ Other antenna

⑥ Your intenaly used PCB antenna patten designs

 

2. Smith Chart Simulation tool(http://www.fritz.dellsperger.net/) can be used for parrel and serial capacitance

and R value calculation of your TRF7970A EVM schematics antenna matching circuit with above antennas?

 

My two advice requests come from TRF7970A using product developing finel stage.

While developing peer-to-peer communication between TRF7970AEVM with smart phone,

distance and angle between TRF7970AEVM and smart phone are big issues.

The distance between TRF7970AEVM and smart phone in peer-to-peer communication has best communication distance length.

This length can be found while smart phone closer to TRF7970AEVM from far distance.

When best NFC peer-to-peer communication distance length reachs then peer-to-peer communication start.

The distance between TRF7970AEVM and smart phone become lesser then this best length then peer-to-peer communication

become stop andt the distance become longer then this best length then peer-to-peer communication also become stop.

 

I used TI’s TRF7970A_RW_1.02.05 firmware that received from Mr Ralph Jacobi on ‘16.09.18

And my TRF7970AEVM clone is same as TI’s TRF7970AEVM but only MPU changed from MSP430F2370

to MSP430F5529 for to execute TRF7970A_RW_1.02.05 exc code size.

 

The angle between TRF7970AEVM and smart phone also has best angle while P-t-P(Peer-to-Peer communications).

And small allowable angle margin from best angle.

 

The distance allowable margin and angle allowable margin are too small to use P-t-P TRF7970AEVM on smart phone application.

So, I tried to increase NFC antenna performance to increase distance & angle margin by increase antenna size.

But failed to increase antenna performance. I used 100KHz LCR meter to get PCB antenna pattern inductance.

The inductance veries every checking times. Finally, I guess 100KHz LCR is not fit for PCB pattern antenna inductance checking.

I guess quick solution to get good performance NFC antenna is selecting on the shelf.

 

There are some kind NFC reader antennas.

I guess large antenna is best. But another thinking select medium size as the best.

Because large antenna must be low electromagnetic flux density and this weaks P-t-P communication.

I requested two advice on TRF7970AEVM P-t-P antenna because I have low experione on low knowledge on NFC antenna,

 

Best Regards

Jeffrey Kang

Deputy General Manger

R&D team

SejuFa.co.kr

 

  • 0
    TI__Guru*** 135355 points
    Hello seokbong,

    All of these inquiries are application specific topics, so I can only offer general advice to help guide you.

    First off, if you use a PCB antenna, please review this antenna design guide: www.ti.com/lit/pdf/sloa241 In general for Peer to Peer, you want a Q of 7 to 10 - and that guide will explain how to achieve this. This also address your question 2 which the answer is yes, but you need to measure the results of the simulated values with a network analyzer as real world has more variances than the simulator can address.

    Note that each NFC smartphone behaves differently. We have seen very large variances in the ideal read range for smartphones depending on both phone and P2P data rate.

    Also please note that Passive P2P universally has been significantly more consistent than Active P2P, so if you are worried about the read range/angle be sure to enable Passive P2P. That's not to say you can't have Active enabled as well, the firmware will poll for Passive P2P first anyways, but the point is, make sure to either use both Passive+Active, or Passive alone, depending on which option gives you optimum performance.