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TRF960AEVM

F Iannce
Prodigy 100 points

I have a TRF960AEVM that I am using to evaluate a switch to ISO15693 tags from ISO14443(A).

 

The reason for the switch is that we would like to get slightly greater distance than we get with the current (Type 2) tags we are using. We would like to get beyond 6-9cm out to closer to 15-20cm.

 

Given that 15693 tags require a weaker magnetic field, and are supposed to therefore work at greater distance, I tested 15693 and 14443 comparable size tag detection distance with the TRF960AEVM. Surprisingly, I did not achieve any greater distance with 15693 tags.

 

The tag sizes used were all smaller than the diagonal of the TRF960AEVM coil, from slightly smaller, to quite a bit. But, no matter the size, the difference between comparable 15693 and 14443 tags was not really relevant.

 

The magnetic field strengths required by the two standards are given as ranges. Are the results I’m seeing due to the field strengths required being more comparable at the low power and smaller coil size of the TRF960AEVM, resulting in a negligible difference? I do not have the NFC expertise to really understand this immediately.

 

Any help would be appreciated!

  • 0
    TI__Guru* 91206 points

    F lannce - 

    if you want longer read range, you will need larger antenna and/or a retuning of the EVM antenna (currently the BW is set for ISO14443A/B and should be halved for best performance with ISO15693). There is a spot to connect external antenna on the EVM and then you need to depopulate R3 to disconnect the onboard antenna.

    for example - if you want ~16cm with a large rectangle tag, then you will need about a 10cm diagonal antenna (meaning ~7 to 7.5cm square antenna), for the smaller tags it depends on how small they are - if you can let me know what tag size you are focused on  - can have a look at that for you in our lab

  • 0 in reply to Josh Wyatt
    Prodigy 100 points

    Josh - Thanks for getting back to me!

    I will perform some antenna experiments more in line with 15693-only detection (e.g. correct BW, ~1MHz).

    As for your offer to do some lab experimentation, I very much appreciate it - you are probably way better set up for this than I!

    Currently, we use 35mm 14443 round tags. As you would expect (using d=2x diam.) rule of thumb, we get about 7cm on average detection. We would like to try to stay in the 30-35mm tag diameter range, but extend this distance as much as possible using 15693 - what do you think we can achieve if the reader coil is designed for this target size? BTW - I put a 25mm diagonal square 15693 tag we would love to use over the TRF7690A EVM, but only get about 36-44mm, depending on location within/over the EVM coil. Just to see ...

    As a quick and dirty experiment, I increased R6 on the EVM to 1.5K to manipulate the Q. I got about 4-5mm extra distance on the small 15693 tags, up to about 15mm extra distance on the comparable size 15693 tags. But, oddly enough, I also got about a 6-7mm increase on the 14443 35mm tags.

  • 0 in reply to F Iannce
    TI__Guru* 91206 points

    Here are some rough measurements i made today - can do more - what size is your reader antenna again?

    7840.Read_Ranges_Antennas_10_2014.xlsx

  • 0 in reply to Josh Wyatt
    Prodigy 100 points

    Hi Josh - Thanks for the measurements! Gives me a much higher degree of confidence in results I've been getting here, too.

    It seems clear to me that boosting the Q range possible (e.g. 15693) adds significant read range, even with the smaller tags, which was my original question. Thanks. But, it seems equally likely we're not going to get quite the range we want at the tag size we want, although if we can move to a slightly larger tag, we get a good boost (per the 45mm tag entry in your spreadsheet, and testing here).

    With regard to the spreadsheet, I noted some pretty significant differences between similar size tags - I'm guessing that has to do with tag turn count,  probably, or other significant tag implementation differences?

    To answer your question about the reader antenna size - that's the area where I have the most flexibility. We originally were thinking about roughly the same size as the target tag size (slightly bigger) for best field concentration, but your tests show a little bigger might be even better (but, not too big). Also, something else that helps us is that the range is good for rectangular implementations, which helps us fit the product ID better (if it's not too rectangular, orientation doesn't seem to have too deleterious an effect).

    So, thanks for the help. As I said, this determines our move to 15693, and answers my original question. If you have any other comments on the above discussion, I would certainly appreciate hearing them!