Short-range transmission using OAM-carrying waves generated by uniform circular arrays

The orbital angular momentum (OAM or vortex) waves are expected to provide ten-fold and larger increases in wireless data rates, required for short-range communications within the beyond 5G and 6G concept of all-connected life and industry. We address the specifics of short-range communications employing OAM-carrying waves generated by small uniform circular arrays (UCAs) at lower, i.e., 10 GHz, transmission frequencies. Comparing the link budgets obtained using (i) asymptotic analytical formulas, (ii) numerical electromagnetic simulations, and (iii) measurements on two pairs of manufactured prototypes comprising 8 microstrip-patch-element UCAs, we point out the limitations of simplified models which do not account for various effects, such as coupling, parasitic radiation, and insertion loss. The observed effects are expected to be relevant at millimeter-wave frequencies as well.