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RFID vs RF IC through/underwater



Jan 1, 1970
Hi there,

From my understanding RF-Tag technology is still sketchy so maybe it's
not the best solution for my need.

What I need is a small transmitter operating at a range up to 1 meter
(greater than 2 meters is actually not desirable). I am looking for
frequencies no higher than 27 MHz as the medium the application is
operating in is water or a water/air combination.

Most of the RFICs that I have found begin their operation at 100MHz
and tend to be in the 300MHz - 450MHz range. I believe this will be
too high for my needs.

TI produces RFID chips in the 134kHz and 13MHz range and this seems
very desirable (has a range of 1 meter and has a package size of only
1mm x 32mm). What is holding me back here is the cost of the readers.
I believe part of what makes the cost so high is that the reader needs
to generate a large magnetic field to power multiple transmitters in a
relatively large area (1 meter radius?). My thought here was to
combine the RFID chip with it's own powersource. Now the power source
only needs to work in the 1 - 30 mm range, and only for a single

Any idea of what this power source would look like? I realize it may
double or triple the size of the RFID package - and that's okay - much
larger than that may not be. The power doesn't need to be continuous,
but I would like to be able to broadcast 2-3 times a second or so
using a quarter size battery.

Looking forward to your suggestions and feedback.


Rich Grise

Jan 1, 1970
Actually, water is opaque to most, if not all, of the RF part of
the spectrum. You'd be much better off with a tiny sonar pinger -
you could probably get a piexo element just a few mm across ...

Good Luck!