Hi, I was wondering if small (1cm diameter max) uhf battery-less accelerometer exists. For the love of me I can’t find any and I’ve been searching for a while now. Any help would be much appreciated.
I need to be able to put a tag on an object and read it’s orientation with an antenna, it should be powered only during the read because between reads could elapse some time and batteries are not a good solution.
Something like this https://www.youtube.com/watch?v=SKQ3wkA … =emb_title but without the whiskers.
We don’t have much, but…the smallest we make is 24.65mm by 7.62mm https://www.sparkfun.com/products/20176 , though it does not have a battery…
The smallest contained unit with a battery is this one https://www.sparkfun.com/products/15170
Might also consider https://www.sparkfun.com/products/19426 with a small external lipo 
First of all thank you very much for your answer.
However that’s not quite what I was looking for, essentially I was looking for a passive accelerometer tag.
There is nothing special about the YouTube video. This goes all the way back to crystal radios, AM receivers in which the earphone is powered by the antenna. Anything can be powered by radio waves, if you can extract sufficient energy. You need an appropriate transmitter, receiving antenna and rectifying circuit, designed to meet the power needs of the receiving device.
Note that passive RFID tags do not transmit data. The ID signals from the transmitting station result from detecting the power absorbed by the tag, which the tag modulates. Viewing the same process differently, a receiver can detect the backscatter from the tag antenna (that is, the RF power that is not absorbed).
Your task is to come up with a low power accelerometer and CPU, then figure out how to power the combination from whatever UHF source you choose , modulate the receiving antenna properties appropriately and finally, detect the resulting data.
Read about “The Thing”, a passive UHF listening device invented by the Russians and used to spy on conversations involving the U.S ambassador to Moscow, between 1945 and 1952.
All it had was an antenna, a resonant cavity and a membrane that acted as a microphone.
https://en.wikipedia.org/wiki/The_Thing … _device%29