[DoctorOetker]

I don't believe the claim is radio echolocation, but radio spectroscopy.

I didn't read the paper yet, but I predict from the comments in this HN thread, that the proposed system is essentially a dielectric spectroscopy setup optimized for glucose detection (or any number of proxy byproducts/complexes/etc..)

Check this wikipedia page for example: https://en.wikipedia.org/wiki/Dielectric_spectroscopy

Look at the picture on the right, from typically lower to higher frequencies there is the motion response of ions, the reorientation response of molecules with a dipole moment, the excitation of vibrational modes in a molecule and the electronic excitation of electrons switching orbitals...

EDIT: since I have not read the article, I do not vouch for its authenticity (above my paygrade)