RFID Receiver design for Multiple frequencies

Discussion in 'Wireless & RF Design' started by rocky.ak, Jul 27, 2017.

  1. rocky.ak

    Thread Starter New Member

    Dec 2, 2016
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    I am trying to design a receiver circuit which can detect and retrieve information from RFID Tags which operate at different frequencies, namely 124 KHz, 128 KHz and 134.2 KHz. I need to design a receiver circuit which can detect tags of those 3 frequencies and retrieve information from it.(Basic RFID receiver but instead of 1, I need to detect tags of 3 different frequencies). Can anyone suggest any material, links or correct me if I am wrong, I believe it's possible right? Thanks in advance.
     
  2. geoffers

    Active Member

    Oct 25, 2010
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    Hi,
    I depends on the type of transponder, some modulate the field, others wait for a break in the field.
    If its just one type its going to be easier, for modulation types look at atmel u2270b as a front end chip or em4095, these data sheets will give you a idea of what's involved :).
    I think unless you need to differentiate been transponder types, setting the frequency of your reader field to the middle of the range you need to read will probably activate the ones at either end. They're not too fussy.
    For the other type of transponder look at the tms3705 .
    Good luck,
    Geoff
     
  3. rocky.ak

    Thread Starter New Member

    Dec 2, 2016
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    Thank you :)
     
  4. rocky.ak

    Thread Starter New Member

    Dec 2, 2016
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    Hello, I have a basic doubt. I trying to retrieve data from passive RFID tags which are of the following frequencies, 124 kHz, 128 kHz and 134.2 kHz so I need to activate those passive tags from my base station using the concept of mutual inductance I suppose. So I had been trying to design a standard coil through which I will be transmitting carrier signals of frequencies 124, 128 and 134.2KHz (using AD9833) for equal interval of times, such that for example whenever a 124 kHz passive tag is over the base station coil, I will transmit a carrier signal of 124 kHz such that both the coils resonate at 124 kHz frequency(pls correct me if I am wrong) and thus power is transmitted to the passive tag and it activates and responds back wrt the data present inside the tag and so on..So my question is what exactly should be the inductance value and design constraints of the coil which I will be using in base station? Thank you!
     
  5. geoffers

    Active Member

    Oct 25, 2010
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    Hi,
    If your starting from scratch I would recommend you use a front end chip, you can then use your arduino to decode the demodulated output.

    Both the em4095 and u2270b have built it coil drivers, check out priority1 website, they have some example circuits and coil values to use.

    The coil itself is part of a lc tank so you will need to tune it to its resonant frequency to get the best performance. This means unless your going to use multiple coils and capacitors, you will have to pick one frequency.

    I've used the u2270b quite a lot with lots of different coils, the transponders I used were designed to work with a activating field of 134 kHz, however they responded as low as 120khz and as high as 150khz (I think?, this is from memory!)

    I think if you set up for the middle frequency you will be able to read both sides. What protocol are you using?

    Google, an678 , an680 from microchip, they should help.

    Its a windy road, good luck.
    Geoff
     
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  6. rocky.ak

    Thread Starter New Member

    Dec 2, 2016
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    We are challenged to make Rx base station which can do FDX-A(125 and 128 kHz with FSK/PSK), FDX-B(134.2 kHz with PSK) and HDX(134.2 kHz with FSK) protocol based passive tags. So I have been looking for modules which can do FSK, PSK and detect all the tags which work at 125, 128 and 143.2 kHz range(Correct me if I am thinking in wrong way). I will set the coil with frequency around 134 kHz and I believe as you said, it would detect all the 3 frequencies.
     
  7. geoffers

    Active Member

    Oct 25, 2010
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    I think your right, I have used hdx transponders with the tms3705 with FSK , but the others were fdx with ask on the u2270b. I've not used psk so might not be much use!
    Cheers Geoff
     
  8. rocky.ak

    Thread Starter New Member

    Dec 2, 2016
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    Hello Again!

    Thank you for the response. I am really confused with this ISO standards 11784 and 11785 and messing up everything. So, like you said, does FDX-A/B uses ASK(AM-PSK) and HDX uses FSK only?. If that is the case, I can design an antenna which can resonate close to 134.2kHz and I should be able to detect data from 125&128kHz tags too(making my antenna so strong that it can produce enough amplitude to retrieve the data from those tags even with higher reflection coefficient as both the coils won't be resonating at similar frequencies). Could you please give me a clarity regarding the modulation schemes used in FDX-A and FDX-B and what about different encoding schemes?(Manchester, Bi-phase, PSK). Thanks!
     
  9. azimmali

    New Member

    Aug 10, 2017
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    Hi Geoff,
    The project is for animal microchips. It is pretty unclear if HDX is used in microchips. The ISO documents mention FDX using AM-PSK and HDX FSK. I did read that HDX microchips are used in places where there is a lot of electromagnetic interference. I did go through a sample code (.ino) where there is no mention of the modulation schemes, but of encoding - Manchester/BiPhase. I would like to know if there could be a confirmation on what modulations do either of the protocols use. Please note: FDX has FDX-A and FDX-B.
     
  10. geoffers

    Active Member

    Oct 25, 2010
    277
    14
    Hi,
    Is there two people on the same project here?
    The iso 11784/85 standards are fairly clear, both fdx-b and hdx are used for animal Id. That's what I've worked with.
    I don't know much about fdx-a.
    Hdx transponders tend to have better range than the fdxb type so if that's what your working with I would tune your coil to the fdx frequency, the hdx will still work well ( in my experience ! :) ).
    Did you check out the priority1 website? There's good stuff there, there is also a microchip app note for the different protocols. I will try and find it!
    Have fun , Geoff
     
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  11. rocky.ak

    Thread Starter New Member

    Dec 2, 2016
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    Hello Again!

    Well, things are clear now, I don't have to worry about HDX and work on FDX only. Well FDX uses Amplitude modulated PSK so I had been looking for a circuit which I can use to demodulate such signal. You said that you had worked with fdx-b, can you provide any reference material to design the transceiver module for it. I have checked Priority1 design website but I couldn' t find any design reference material to make it and I wanted to design the transceiver by myself using EM4095 or something much simpler, please let me know if you have any reference materials for designing RFID transceiver which can work for fdx and work at 125,128 and 134.2kHz(I think designing a powerful antenna and resonating it with 134.2kHz carrier can even work for 125 & 128kHz or else I had to design using variable cap which I feel more bulky, please correct me if I am wrong). Thank you!!
     
  12. geoffers

    Active Member

    Oct 25, 2010
    277
    14
    Hi,
    Have you checked out the datasheets and app notes for the em4095? Also the datasheets and app notes for the u2270, most of the info you will need is in those sheets used with the iso standards for which ever transponders you need to use.
    I've found the microchip document that is very useful ds51166c, its long and mostly tedious :)!
    Do you have access to a scope? You will need it if you're going to do this with any of the above.
    Cheers Geoff
     
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  13. rocky.ak

    Thread Starter New Member

    Dec 2, 2016
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    Hi,

    Yes, I have read the data sheet and all the technical papers of EM4095, U2270 is pretty old and not used much in the industry so I was thinking to stick with EM4095, although I have gone through U2270 data sheet too. DS51166C by microchip document, as you said is pretty good to begin from scratch but that document covers more about customizable chips by microchip and kind of misleading in later stages, because I need to work only on FDX which uses Amplitude modulated PSK(I was thinking to design an AM demodulator followed by PSK demodulator, correct me if I am wrong) Thanks!!
     
  14. geoffers

    Active Member

    Oct 25, 2010
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    That sounds like the right way to go about it, but as I said I haven't used psk before so am not really qualified to help!
    I did have a look at the psk receiver schematic in the microchip app note and it looks much more complex than a simple ask receiver that will pick up fdx b tags.

    I guess with a arduino running fast you could code a lot of the detection but pic's are my area so I'm not much use there either!

    Hopefully someone on here can shed more light on this than me, let us know how it goes. I'm interested!

    Cheers Geoff
     
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