  In this paper we document for the first time some of the effects of
self-healing, a property of orbital-angular-momentum (OAM) or vortex beams, as
observed on a millimeter-wave experimental communications link in an outdoors
line-of-sight (LOS) scenario. The OAM beams have a helical phase and
polarization structure and have conical amplitude shape in the far field. The
Poynting vectors of the OAM beams also possess helical structures, orthogonal
to the corresponding helical phase-fronts. Due to such non-planar structure in
the direction orthogonal to the beam axis, OAM beams are a subset of structured
light beams. Such structured beams are known to possess self-healing properties
when partially obstructed along their propagation axis, especially in their
near fields, resulting in partial reconstruction of their structures at larger
distances along their beam axis. Various theoretical rationales have been
proposed to explain, model and experimentally verify the self-healing physical
effects in structured optical beams, using various types of obstructions and
experimental techniques. Based on these models, we hypothesize that any
self-healing observed will be greater as the OAM order increases. Here we
observe the self-healing effects for the first time in structured OAM radio
beams, in terms of communication signals and channel parameters rather than
beam structures. We capture the effects of partial near-field obstructions of
OAM beams of different orders on the communications signals and provide a
physical rationale to substantiate that the self-healing effect was observed to
increase with the order of OAM, agreeing with our hypothesis.
