Possibility of Flex xEM

Will it ever be possible to make a flex implant with the ATA5577 chip? I currently use my xEM to unlock the doors at work. But it would be super amazing to have it in a Flex form-factor for the increase in range/performance.

If not, why isn’t it possible? Would it be possible if it was made drastically different from the other flex implants? Like, say, much bigger in surface area?


I’m with you here. Can’t speak for Amal or any of his team but it doesn’t seem that hard. I do know they have a number of other projects underway though so it may not be top priority.

It’s not a top priority but one big reason we don’t want to explore it is the sheer size of the wire antennas involved. We can explore some ideas but you’ll basically need a pretty wide incision with a scalpel to make it work, and performance won’t be all that great either compared to the performance increase of the HF flex versions.

Still, if it’s interesting to anyone we might explore a custom job.

Thanks for the reply, Amal. Could you possibly expound more on what you mean by the size of the wires and the incision width? Are you saying that the gauge of the antenna wire would be way larger? Or are you talking surface area when the antenna is all laid out flat?


λ = c/f

The diameter of an antenna coil is a function of the wavelength of the target signal. For HF signals (13.56MHz) the wavelength is “small” (~22m) whereas with a 125kHz signal the wavelength is much larger (~2.4km). You can do fractions of the wavelength (1/2, 1/4, 1/32) but the greater the difference between reader and tag antenna fraction, the more problems you’ll have with coupling. So basically the xEM flex would be a small fraction of the wavelength and not couple much better with readers (while still being physically larger than the flexDF)

If you want more info you could check this out:


That’s an excellent explanation, however all the math and digikey example center around electric field emitters. The problem is similar though for a passive magnetically coupled device like the xEM. The issue is almost the same, but in short the tag and reader are L/C resonators and the inductance required to resonate at the desired frequency requires a lot of wire. Also, the smaller you make your coil diameter, the less inductance it has for a given wire length… so it’s simply a challenge to get enough wire packed into a small enough space and also continue to have enough surface area to interact with the source field in an efficient manner.

At times I refer to this stuff as black magic.


I wonder what sort of Price we would be looking at?

I have been doing some experimenting with some 125kHz products
I dis-assembled what I hoped to be 1 ring :ring: to rule them all, but to no avail, the antenna ran the circumference of the ring. and difficult to extract ( No photos, unfortunately, and I have since thrown it away )
I then got some RFID wrist bands, that look promising, with a similar length and width of a Flex NT, however the height is substantially greater (~x10) at about 4mm.
The chip is a EM410x rather than the xEM ATA5577 though.
Read range was good,
a key fob to DT Acces controller ~75mm
Wristband ~65mm
I’m not sure what to expect with it as a Flex implant but it looks promising???

[+] EM410x pattern found

EM TAG ID : 6C009D0A14

Possible de-scramble patterns

Unique TAG ID : 3600B95028
HoneyWell IdentKey {
DEZ 8 : 10291732
DEZ 10 : 0010291732
DEZ 5.5 : 00157.02580
DEZ 3.5A : 108.02580
DEZ 3.5B : 000.02580
DEZ 3.5C : 157.02580
DEZ 14/IK2 : 00463866759700
DEZ 15/IK3 : 000231940378664
DEZ 20/ZK : 03060000110905000208
Other : 02580_157_10291732
Pattern Paxton : 1823557652 [0x6CB14814]
Pattern 1 : 6750424 [0x6700D8]
Pattern Sebury : 2580 29 1903124 [0xA14 0x1D 0x1D0A14]

[+] Valid EM410x ID found!

Yeah they cram a bunch of wire in the z-axis and we just can’t do that for a flex… so it must spiral outward… and you get a pretty giant flex at that point.

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